How
WHEN MATERIALS COME ALIVE
stay
E - GU IDE # 03 - SEPTEMBER 2025 - BY
A practical guide for outdoor design
No design is possible un which you design are co
Ludwig Mies V
2
until the materials with ompletely understood.1
Van Der Rohe
emi Extr
s agre
es!
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FURNITURE ASSEMBLY / Extremis production facility
Carefully written by the Extremis design & development team for all who are interested in acquiring material knowledge for outdoor design.
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A guide to E- GUIDE # 03
Outdoor Materials
SEP. 2025 Free publication. For more information and the latest revelations, please head to our website
www.extremis.com
“When do materials come alive?” We believe materials come alive when they fulfill a purpose—function, sensorial, and aesthetical—
exceptional functionality that stands the test of time, something to love for a lifetime and pass on to the next generation.
through their integration into thoughtful design. New
Extremis now has over 30 years of experience in outdoor
materials in a product often look, feel, and perform
design, with durable products sold and used worldwide
well. However, over time, materials age and deteriorate,
in the harshest outdoor conditions. By working with
gradually losing their purpose—especially outdoors,
many top-tier suppliers and research centres, we keep
where conditions can be brutal. As pioneers in outdoor
up-to-date with the newest advancements in material
furniture, we at Extremis are committed to sharing
science and technologies.
our expertise, empowering you to make informed, sustainable design decisions and answer the question:
Our expertise has always been in metals and wood, yet
“How do materials stay alive?”
better comfort and shading for our furniture. Although
Extremis is a Belgian-based company founded in 1994 by Dirk Wynants, son of a cabinet maker. With his carpentry roots, design education, and an introduction to the metal business through his family-in-law, Dirk started with his first design idea, the Gargantua table, a combination of metal and wood. This marked the beginning of a collection of innovative design furniture that offered new solutions — outdoor furniture with
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this quickly expanded to textiles in order to provide we also use other materials like natural stone, concrete, plastics, composite materials, rubber, etc., for this guide, we want to stick to our core expertise.
GARGANTUA/ Design by Dirk Wynants in 1994
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Index Outdoors vs Indoors
10
It’s brutal outdoors!
12
Embrace the beauty of weathering
16
Design wisely
18
Choose wisely
20
Wood
8
22
Introduction to wood
24
Forest management
26
Durability & hardness
28
Wood is alive!
30
Wood sustainability
36
Wood maintenance
39
Metals
40
Introduction to metallurgy
42
Three must-known metals
44
The war against Corrosion!
52
Metallic coatings
58
Organic coatings
64
Metal recycling
68
Metal maintenance
70
Textiles
72
Introduction to textiles
74
Three must-know fabrics
76
Textile finishes
79
Textile sustainability
82
Textile maintenance
84
Sustainable Design
86
Fast design ≠ sustainable
89
Impact in the long-run
90
A holistic approach
92
Conclusion
94
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Outdoors vs Indoors Designing a product for outdoor use requires a completely different approach than for indoor use. A designer must carefully consider the materials used and how they react to the environment. Only then can we ensure that the materials truly come to life in the best possible way. Let’s take a closer look at some key factors when designing or selecting a product for outdoor use.
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Introduction _ 11
It’s brutal outdoors! No material is entirely resistant to the test of time and
Just as ultraviolet (UV) radiation causes skin cancer in
the forces of mother nature. Eventually, everything
humans, it also degrades the quality of many materials.
will age, fail, or break. Successful design engineering
For example, many plastics will become brittle and crack
focuses on delaying that moment as much as possible
when exposed to high levels of UV radiation. Indoors,
while understanding when and how failure might occur.
this is less of a problem as there is less natural light and
It also involves anticipating potential dangers and
many windows already come with a UV-blocking film.
ensuring the ability to repair or replace damaged parts. To achieve this, reputable manufacturers subject their products to rigorous simulations and testing, pushing
The obvious complication of wind and storms is seeing things sail away or break. This is often a problem for
them to failure to understand their limits fully.
cheaper, lightweight furniture. However, even heavy
Temperature fluctuations not only have a big impact
hazard. Securing anything that shouldn’t fly is crucial,
on comfort, touching extremely cold surfaces in
especially in rooftop environments or public spaces.
winter or hot surfaces in summer, they also impact the way some material age. Not only do materials heat because of high atmospheric temperatures, but also by exposure to direct sunlight. This phenomenon is especially noticeable in materials that absorb and retain heat well, such as metal, asphalt and certain types of stone and concrete. Color choices will influence this as well, depending on how much they reflect or stimulate absorption. Humidity levels are not constant. Low humidity values can reach near zero in very dry areas such as deserts (Atacama Desert, Death Valley) and low-lying arid regions (Dead Sea). High humidity values can reach 100% in tropical rainforests, coastal areas during rain, and swamp areas. Humidity also changes according to climatic conditions. In the UK for example, summer humidity is 15% and winter humidity is 20%. Extreme levels and fluctuations of humidity can have significant consequences for the performance of various materials.
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tables with strong umbrellas can become a significant
Environmental factors such as industry, salt, fauna & flora, mold, fungi, insects, etc. significantly impact materials used outdoors, affecting their durability, performance, and appearance. The corrosion classes, are used to categorize the degree of exposure of materials to environmental influences. These classes are standardized and help select materials suitable for specific environmental conditions.
INDOORS
≠
OUTDOORS Temperature
Celsius and fahrenheit scales
-50°C
10°C
30°C
70°C
-60°F
50°F
90°F
120°F
Humidity Relative humidity scale
0%
10%
20%
100%
60%
UV Radiation Index Scale
0
2
3
5
6
7
10
11+
Wind & Storm Beaufort scale
0
1
12
Corrosion class ISO & ASTM standard
C1
C2
C3
C4
C5
Mild
Moderate
Severe
Very Severe
Extreme
Introduction _ 13
The value paradox of outdoor design
Quality encompasses factors such as durability, reliability, performance, and craftsmanship. In essence, it’s about delivering excellence in what you
We spend on average ~90% of our time indoors2, therefore, we usually value indoor design higher. Needless to say this difference is bigger in colder climates and smaller in warmer climates. Outdoor design, however, faces far greater challenges due to the harsh conditions it must withstand— particularly in extreme climates. This necessitates the use of more expensive materials and innovative solutions to ensure durability. For example, developing a longlasting outdoor sofa is significantly more complex and costly than developing an indoor one. Yet, paradoxically, most people allocate a smaller budget to their outdoor furniture compared to their indoor pieces. This disconnect between perceived value and actual cost presents a major challenge for outdoor design companies, as they strive to balance durability, aesthetics, and affordability in their products. A better understanding of perceived versus intrinsic value helps us to understand how to make better decisions. Perceived value refers to the subjective worth or importance that a customer assigns to a product based on their personal beliefs, attitudes, and experiences.
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offer. Perceived quality is not always aligned with the actual, intrinsic quality of the product but rather how consumers perceive it based on various cues and marketing strategies. Often, objects attract attention and are picked up impulsively or out of curiosity because of their visual appearance, influenced by Color, Material, and Finish design (CMF)3. This triggers an immediate emotional connection. Materials derived from original precious minerals and metals are perceived as higher-end. Other materials, like plastics, have a lower perceived value due to their disposable nature and recent associations with environmental issues. However, their ease of manufacturing in high volumes at relatively low cost makes them widespread.
$$$
Actual cost The cost of durable materials
Low
Outdoor
High
Indoor
WALRUS SOFA / Endures all seasons without covers
Introduction _ 15
Embrace the beauty of weathering The unavoidable weathering caused by nature’s elements
COPPER
can dramatically transform the look and feel of a product over time. Signs of aging, such as fading, darkening, or other changes, are often referred to as patina. In some cases, a well-developed patina can enhance a product’s aesthetic appeal, much like a fine wine that improves with age. However, not all materials age gracefully. For instance,
HOT DIP GALVANIZED STEEL
a painted surface marred by scratches or blisters is generally perceived as unattractive. This highlights the importance of understanding and appreciating how different materials age and develop imperfections over time. Recognizing the beauty in natural aging and the
THERMO TREATED ASH
evolution of patinas is essential when selecting and combining materials. By choosing materials that age well and harmonize aesthetically, designers can create products that retain their appeal even as they weather over time.
DID YOU KNOW? The Statue of Liberty’s copper exterior developed a beautiful green patina over the years, initially causing concern among authorities unaware of its protective properties. They attempted several times to let miss liberty be painted.4
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COPPER PATINA / Statue of liberty in New York
Introduction _ 17
Design wisely There are pros and cons to every material. Each material
Metals have a high strength-to-weight ratio, making
is precious and should be used mindfully, according
them stable and durable materials ideal for structural
to its best properties and the intended purpose. To
components. However, touching metals is not always
love design unconditionally and cherish it for as long
pleasant. Because they conduct heat very efficiently,
as possible, materials should work together both
metal surfaces can feel extremely cold in winter and
functionally and in terms of color, material, and finish
uncomfortably hot in summer. Generally speaking,
(CMF) to create a harmonious result.
metals are low-maintenance materials. With a wide
Wood is a natural and renewable material. If not processed too heavily, it requires minimal energy
range of coating techniques available, metals can be produced in a variety of finishes and colors.
to produce. Despite the superior quality of premium
Fabrics are typically used to add comfort. Their flexibility
wood species, wood also has several drawbacks: it
and softness are unmatched by any other material.
can be unstable, requires high maintenance, and may
The variety of textures, colors, and finishes they offer
splinter. However, one key reason for using wood is
is virtually endless. However, unless treated with a
that it is among the best materials for direct contact
protective coating, fabrics tend to absorb moisture
with skin. A study done by The Japan Wood Research
and dirt, which can lead to mildew or mold in humid
Society concluded that contact with wood, unlike artificial
environments.
materials such as aluminum or plastic, natural wood causes no physiological state of stress.5
Wood Unique aesthetics, natural touch and fully renewable.
Metal Durability, Strength, stability, accuracy and fully recyclable
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Fabrics Flexibility, softness, translucency, breathability and lightweight.
Design is a plan for arranging elements in such a way as best to accomplish a particular purpose.6 Charles Eames
PANTAGRUEL TABLE / Extremis
Introduction _ 19
Choose wisely Outdoor companies should strive to create designs that
Choosing colors or finishes can be more than just
are suitable for any environment. However, this is almost
personal taste... You should base your choice of color
a mission impossible, as in many cases, “one size does
on elements such as heat absorption, reflection and
not fit all.” Therefore, offering a wide variety of designs,
maintenance. To pick the right color, consider whether
sometimes even with different finishes and options can
or not it is exposed to direct sunlight. Dark colors absorb
be a good idea.
light and will heat up, while light colors reflect light and stay cooler.
It is then the customer’s responsibility to make the right choice from the assortment. The customer has to select from that collection according to his own needs, while taking into account the specific location where it will be used. What are the local conditions you are faced with—temperature, humidity, coastal environment, etc.? Consider the orientation of the sun, protection from the wind, who and how the maintenance will be taken care of? All these factors come into play when making the right decisions.
Also UV light from the sun will bleach many colors. Only pick saturated colors if you don’t mind them to change slightly over the years. Otherwise make sure that the materials are highly UV-resistant or pick a more neutral color. Only choose a pure white product if you are willing to clean the surface regularly. While a white table may look very appealing in a showroom setting, it will get dirty very fast. The same applies for surface finishes, matt surfaces collect dirt and are harder to clean compared to glossy surfaces. In case of direct exposure to sunlight, possibly disturbing reflection should be kept in mind.
IMPORTANCE OF COLOR CHOICE / Extremis color collection Off white Black
Cobalt blue
Earth
Copper brown
Verdigris
Papyrus white
Reed green
Beach beige
Cosmic cream
Pistache
Sun yellow
heat absorption*
White
a lot
maintenance
neutral no / or low
reflection* SAFE ZONE
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Color infographic
*effect on colored surface when exposed to direct sun light
Introduction _ 21
Wood Can you name another material that grows naturally, is strong enough for construction, stores CO2 , and possesses a unique natural look and feel like no other? Wood is a porous and fibrous structural tissue found in trees and other woody plants. It is an organic material—a natural composite made up of cellulose fibers embedded in a matrix of lignin.7 In this chapter, you will learn more about different types of wood, their properties and methods to enhance them.
“Partly dead, partly alive, wood combines the material and the immaterial, the past with the present, the tangible with the imagined.”8 Philip Ursprung
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Solid Woods
Engineered Woods
Engineered wood products are created by binding wood-derived materials, such as (recycled) fibers or veneers, using adhesives to form a composite material. While these materials can closely resemble solid wood in appearance, they may not be as durable for long-term outdoor exposure unless specifically treated for that purpose. Additionally, the manufacturing and disposal of the adhesives used can contribute to a notable carbon footprint and hinder further recycling. For these reasons, we prioritize the use of solid wood, which tends to be more sustainable and environmentally friendly.
Wood _ 23
30 YEAR OLD GARGANTUA TABLE / Treated properly every season
Introduction to wood Cells are created on an annual cycle surrounding a
Woods are classified according to their botanical origin
tree. These active woody cells are called sapwood,
as softwood or hardwood.
because they are still forming their cellulosic walls and conducting sugars, nutrients and water for the whole tree. Sapwood is weak and unstable, with a high moisture content, which causes it to shrink, stain, and
Softwoods, which come from cone-producing trees, have a simpler structure, making them lighter and easier to process. Visually, softwoods are paler than
decay quickly.
hardwoods, but this does not mean that lighter wood
When the resins become crystallized, heartwood is
be used outdoors, but they generally require more care
formed. Heartwood is darker in color, drier, more
and maintenance to ensure their longevity compared to
compressed, stronger, and more durable, serving as
hardwoods.
types are inherently of inferior quality. Softwoods can
a stable core that allows the tree to continue growing. As a tree ages, the ratio of heartwood increases, thus
Woods from broad-leaved trees, such as fruit trees, are
increasing the quantity of durable wood within the tree.9
known as hardwoods. These trees experience prolonged growth and have a very dense fiber structure. While hardwoods are usually more difficult to process due to their hardness and density, the finished products are far more resistant to outdoor elements. Despite the greater variety of hardwood species, softwoods now dominate
Bark
commercial wood production due to faster drying and easier processing.
Sapwood
Tropical hardwoods are a subset of hardwoods sourced from trees that grow in tropical regions with warm, humid climates. These woods often exhibit superior
Heartwood
strength and natural resistance to decay.
Pith
Hardwoods Softwoods 0
350
700 General wood density (kg/m³)
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1250
EXAMPLES OF WOOD SPECIES / Classified by their botanical origin
Softwoods
Hardwoods
Tropical hardwoods
Fir
Oak
Teak
Pine
Ash
Mahogany
Larch
Chestnut
Rosewood
Redwood
Beech
Jatoba
Spruce
Walnut
Iroko
Cedar
Maple
Afrormosia
DID YOU KNOW? It is generally believed that all woods float, but some hardwoods (like lignum vitae or ebony) have a density greater than that of water (>1000 kg/m³), causing them to sink.
WOOD WEATHERING TESTS / Extremis
Wood _ 25
Forest management Timber from hardwoods that grow slowly, especially tropical hardwoods, can be unsustainable if they are harvested irresponsibly, leading to deforestation, habitat destruction, and biodiversity loss. Many forests in the Amazon, Southeast Asia, and Africa have been heavily exploited for these woods, often through illegal logging.10 However, if forests are not used for sustainable timber, they lose their economic value and might be cleared for cattle ranching, soy farming, or palm oil plantations, which cause even worse environmental damage. In some areas, abandoned land is taken over by slash-and-burn agriculture, leading to soil degradation and long-term deforestation. Sustainable forestry practices like FSC® & PEFC can ensure the continued availability of wood while protecting forests.11 12
The Forest Stewardship Council (FSC®) is a non-profit
Due to dissatisfaction with the requirements, FSC was
organization. A timber company or any other company
not a perfect match with the smaller private owners of
that wants to become FSC certified, use the FSC label,
European forests because of high certifications costs.
and process and/or trade FSC certified products must
Therefore, Programme for the Endorsement of Forest
cooperate with an audit. A chain of custody system is
Certification (PEFC) organization was established as
used, whereby the wood is tracked from logging to the
a competitor. Since 2004, PEFC is active worldwide,
final product. The FSC label is not a guarantee of quality;
including in tropical forests. The PEFC label is
it merely serves as proof that the wood primarily comes
consistent with the Sustainable Development Goals
from forests managed according to the FSC standard.
(SDG) from the United Nations.
This standard is internationally regarded as a guarantee of responsible forest management.
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TREE ANALYSIS AND RESEARCH / by forestry worker
Europe
North America
Asia
Africa
Tropical hardwood Temperate hardwood
South America Australia
Softwood Mixed
DISTRIBUTION OF FORESTS / by categories of wood13
Wood _ 27
Durability & hardness You’ll quickly notice that there are many rankings to sort wood types on their quality. Most commonly used are durability classes and hardness ratings. These rankings tell you a great deal about general wood characteristics, but it’s not a hard science. There are also other factors in play, like the origin or climatic conditions. As different soil chemistry will lead to different qualities in the wood. For example, Burmese Teak that is derived from the species’ old-growth forests tends to be of far better quality than Plantation Teak.14
Durability class
Janka hardness
The European standard EN 350.215 is conventionally
The Janka hardness test, specified in ASTM standard
used to classify solid wood types into five durability
D 14316, measures the resistance of a wood sample to
classes. These only express the wood’s natural
denting and wear. It measures the force required to
resistance to wood decay fungi, beetles, termites or
embed a steel ball into a sample of wood. Hardness is an
marine organisms. The layout is based on a simple test:
important factor when it comes to flooring, as a floor is
a sample post is partially inserted into the ground. The
exposed to a lot of wear from contact with shoes, pets,
longer the lifespan of the sample, the more durable the
etc., especially in high-traffic areas such as offices or
wood. The methods can be applied either to individual
retail shops. On the contrary, wooden cladding doesn’t
wood species, batches of wood, processed wood-based
need a lot of hardness, as there is little to no contact.
materials, including heat-treated, preservative-treated
Furniture falls somewhere in between. There is still a lot
wood and modified wood.
of contact, but it’s usually not that hard.
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Durability Class 5
4
3
2
1
0 - 5 years
5 - 10 years
10 - 15 years
15 - 25 years
25+ years
Natural Teak Thermo Ash
Ash Ayous
Thermo Ayous Iroko Oak Plantation teak
All sapwood is classed as being not durable
Cedar Larch Douglas fir Pine
Janka hardness scale 0
1000
2000
3000
4000
lbf
Poplar Heart Pine Teak North American Walnut Iroko Beech Ash Oak Maple Wenge Merbau Mahogany Rosewood Jatoba Cumaru Brazilian Walnut
Wood _ 29
Wood is alive! The older we get, the more wrinkles and gray hair we (usually) get. It’s the same for wood. Although tough
Shakes and cracks
in character, wood shows the signs of age like any
Nevertheless, even with premium perfectly dried wood,
other living thing. As a consequence of exposure to the
after a while, small cracks and crevices can still appear,
elements, its patina will change over time.
these are called shakes. Shakes are a defined lengthwise separation of the wood along the grain, usually occurring between or through the rings of annual growth. In nature, trees are not created equally. The beauty of
Moisture content
wood lies in the different physical characteristics of each
Wood will absorb or release moisture until it reaches
plank.
an Equilibrium Moisture Content (EMC) with its surroundings. Fluctuations may be more or less cyclical, such as diurnal changes or annual seasonal changes. To minimize the changes in wood moisture content, wood
Greying
is usually dried to a moisture content that is close to
Fresh cut wood has its color because of tannins. Tannins
the average EMC conditions to which it will be exposed.
are organic compounds that are part of the wood tissue
These conditions vary for interior uses compared with
(yellow, brown, or reddish). These tannins are water-
exterior uses in a given geographic location.
soluble and will disappear from the surface due to both
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bacteria growth (mold and mildew) and UV light damage to its exposed surface cell structure. On initial contact
Shrinkage and swelling
with rain, these pigments will bleed out of the wood for a period of time.
As the moisture content in wood changes, shrinkage and swelling may occur. The level at which wood shrinks is not the same in all directions (tangential and radial), which generates stresses within timber during drying.
Uniform moisture content
This can lead to warping and cracking, especially with harsh, uneven drying. Wood shrinkage levels play an important role in wood stability, and this varies depending on the species, origin and maturity of the tree.18
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Uneven moisture content
All wood surfaces will eventually turn gray outdoors. This is perfectly normal and a typical characteristic of wood that doesn’t compromise its structural integrity.
EXTREMIS HOPPER / Ash with ThermoWood® treatment
Wood _ 31
WOOD CLADDING WITH BLACK STAIN AND OIL/ Noa outdoor living
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Wood treatments Once wood has been harvested, cut and dried, it can be treated in various ways to improve stability and durability. Especially less durable woods are treated this way to make them usable for outdoors. Some common wood treatments for outdoor are:
Chemical modification
Wood oiling
There are a number of different chemical and pressure
Wood oil is a protective and decorative wood finish that
treatment processes that can extend the life of wood,
can be applied directly to bare wood and timber. Slowing
sometimes.
down rapid changes in moisture content that would
Whereas traditional preservative treatments often relied
otherwise lead to cracks.
on toxic chemicals that raised health and environmental
Wood oils are predominantly natural products which
concerns, modern approaches such as Accoya®
are easy to apply, as opposed to wood varnishes with
(acetylated wood) and Kebony® (furfurylated wood)
high amounts of volatile organic compounds (VOC).
provide high performance with more environmentally
UV-resistant wood oils will also slow down aging and
responsible methods.
greying, and will even revive a wooden surface’s natural color, bringing it ‘back to life’.
Shou Sugi Ban Shou Sugi Ban, also known as Yakisugi, is a traditional Japanese technique of wood preservation that involves charring the surface of wood to make it more resistant to weathering, pests, and improves fire resistance. The term ‘Shou Sugi Ban’ translates to ‘burnt cedar board’, although other types of wood can be used as well. Shou Sugi Ban has gained popularity beyond Japan in recent years, especially in sustainable and modern architectural design, due to its combination of functionality and aesthetic appeal. Applications are mainly found in cladding & fencing.
WOOD CLADDING WITH BLACK STAIN AND OIL/ Noa outdoor living
Wood _ 33
Thermal treatment Thermal modification permanently alters wood
The figure below shows the 3 phases of a general
properties by heating it to a minimum temperature of
ThermoWood® process.
160°C, much higher than conventional kiln-drying of wood. This process enhances durability, stability, and
1.
In the first step, the wood is placed in a kiln or heattreatment chamber and heated to a temperature of
resistance to rot and pests, without using any chemicals,
100–130°C (212–266°F). During this phase, the goal
making the wood safe to handle and dispose of. Heat
is to reduce the wood’s moisture content to nearly
affects the entire wood cross-section, changing its
zero. Steam is applied throughout the process to
chemical composition and cell structure. Manufacturing
prevent cracking and protect the wood from burning.
process varies depending on the wood species. As the raw materials and manufacturing process of thermally modified wood aren’t overseen by a third party, the
2. Once dried, the temperature is increased to 180–230°C (356–446°F). This high-heat phase
process and product quality may vary significantly
modifies the wood’s structure by breaking down
between manufacturers.
hemicellulose, which reduces its ability to absorb moisture and enhances its resistance to decay.
Conversely, ThermoWood® is a registered trademark owned by the International ThermoWood Association. This trademark signifies wood products made via a
3. After the heat treatment, the wood is gradually cooled down. Steam or water is reintroduced to
patented process developed in Finland in the 1990s. The
stabilize the material and restore a small amount
quality control of ThermoWood® was developed during
of moisture, typically bringing it to a level of 4–7%.
the 90’s collaboratively with Technical Research Center
This ensures that the wood is no longer brittle and is
of Finland (VTT), member companies, and Finotrol Oy.19
ready for practical use in various applications.
General overview of thermowood process
Kiln temperature (°C)
250
200
150
100
50
0
High-temperature drying
10
Thermal modification Conditioning
20 Treatment time (hours)
34
30
40
THROUGH HELL & BACK
EXTREMIS HELLWOOD / Ash with ThermoWood® treatment
Wood _ 35
Wood sustainability
When harvested responsibly from well-managed forests, wood can be one of the most sustainable building materials. Not only is wood fully renewable, but processing and recycling wooden products can also be done for a fraction of the energy expenditure of other building materials, such as steel, aluminum and concrete.20 Trees absorb carbon dioxide, and wood holds it, leading to a lower lifetime embodied energy. Byproducts such as bark and shavings can additionally be used as a biofuel, offsetting energy used in the production process.
36
Solid wood is a blessing when it comes to CO₂ storage
Wood _ 37
OILING HOPPER TABLETOP / Recommended twice a year
38
Wood maintenance Outdoor wood is constantly exposed to the elements, including sunlight, rain, humidity, and temperature fluctuations. Proper maintenance helps prevent rot, warping, cracking, and discoloration, ensuring longevity and aesthetic appeal.
Preventing stains
Preventing mold and rotting
Try to keep food and drink from spilling directly onto the
Wood does well in rainy conditions. However, it is also
wood, especially substances that can cause stains like
important to allow it to dry from time to time, to prevent
wine, coffee, or oil. Spills on wood can be cleaned with a
mold (this appears as little black spots) and rotting.
moist cloth. It is however important to do this quickly to
When mold does appear, treat the wood with vinegar
prevent them from soaking into the material. If the stains
first, before trying heavy anti-mold treatments. If wood
are already to deep, light sanding can be a solution.
gets wet a lot, oiling is a must.
Regular cleaning
Oiling
Dampen the surface with water using a garden hose.
It’s recommended to oil outdoor wood products
Scrub with a soft-bristle in the direction of the grain.
twice a year for general outdoor use, especially if the
Use a mild detergent mixed with water. Avoid using a
wood is cleaned often, as detergents can strip it of its
pressure washer, as this can gouge or splinter the wood.
natural oils. Oiling helps replenish these oils, which
Over time, outdoor wood surfaces will become rough or develop splinters. In this case, sanding will make the surface smooth again. First, allow the wood to dry completely. Then, sand in the direction of the wood grain using medium-grit sandpaper (80-120 grit).
are essential for the wood’s durability and moisture resistance, keeping it protected and looking great. Choose the right oil for your specific wood type and intended use. Always test on a small area first to ensure you like the finish, as wood oil can significantly alter the wood’s appearance. A little oil goes a long way. Use circular motions to ensure the oil penetrates well, and wipe away any excess oil on the surface.
Wood _ 39
Metals The discovery of new metals often changed the course of history so drastically that they are now used to define different time periods in history (Copper age, Bronze age, Iron age). Today, our society is completely reliant on metals, often far removed and much more exotic than the wrought metal ores first discovered thousands of years ago. The science of metallurgy is now one of the most widely researched materials sciences.21 In chemistry, metals are “elements that lose electrons easily, that are lustrous, malleable, and are good conductors of heat and electricity.” 22
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If outdoor furniture was made of gold, it wouldn’t rust!
EXTREMIS GOLDEN PICNIC/ Not actual gold, but anodized aluminum
Metals _ 41
Introduction to metallurgy Around 95 of the 118 elements on the periodic table are
So, how are metals formed? In nature, most metals are
metal elements. However, only a smaller subset is widely
found in combination with other chemical elements.
used in industry due to properties like scarcity, cost,
These natural chemical combinations are known as
and lack of desirable properties. Aluminum and iron are
metal ores. In order to extract pure metals from their
the two most abundant metal elements in the Earth’s
ores, significant energy must be expended.
crust by weight. This, combined with their favorable properties such as strength, durability, and ease of
Extraction
processing, makes them the most widely used metals for
2Fe2O3 H2O
industrial applications. By combining metals with other elements, we create
Metal ore
4Fe + 2H2O + 3O2 Corrosion
Pure iron
what’s called an alloy (e.g. Brass, combining copper and zinc). Alloys have several advantages over pure metals due to their enhanced properties. Alloys that contain iron (e.g. Steel) are also referred to as ferrous metals. Nonferrous metals (like aluminium alloys) are usually more expensive because they are often in higher demand and are generally less abundant than ferrous metals. In addition to the various metal elements, also the way the metal atoms are structured in the atomic lattice is critically important for its properties. E.g. graphite and diamond, where diamond is the hardest material in the world and graphite is as soft as a pencil tip. While in fact they are both merely structural formations of the same base element, carbon.
Conversely, corrosion is the tendency for metals to revert back to their natural, stable state. This breakdown of metals only occur when exposed to a ‘corrosive environment’. That’s why corrosion only takes place at the surface of the metal. There are many different types of corrosion mechanisms. The most known example is when steel reacts with oxygen (O2) and water (H2O). The reddish-brown oxide that is created in this reaction is called rust. Rust that forms at the surface gradually flakes off, exposing the new metal underneath. Metals that are highly resistant to corrosion and oxidation include precious metal like gold, silver, platinum, etc.Unfortunately, because of their rarity, these metals are too expensive to be used anywhere other than special applications or jewellery. The same is true for titanium, copper, lead, etc. While they are not technically considered precious metals, their cost often
Carbon atom
Graphite
42
exceeds what’s acceptable for general applications.
Diamond
If precious metals had been abundant, they would not have been precious.23 Henry Hazlitt
Al
Mg Ti
Cr
Fe
Cu Zn Ag Pt Au
Non-metals Precious metals
Fe
Metals used for industrial pruposes SIMPLIFIED PERIODIC TABLE / metals
Metals _ 43
Three must-known metals While there are many types of metals to talk about, in this section, we will dive a little deeper into three (most) common metals used for architecture and furniture:
• • •
Aluminum Carbon Steel Stainless Steel
DID YOU KNOW? The Eiffel Tower, made of wrought iron, was originally meant to be dismantled after 20 years! Though historically significant, wrought iron has declined, with steel now the preferred alloy of iron.
EIFFEL TOWER PARIS / made from Wrought Iron
44
Metals _ 45
ALUMINIUM EXTRUSION PROFILES/ Custom parts from Extremis
46
Aluminum Aluminum is known for its numerous benefits, most
When aluminum is exposed to a dry atmosphere, it will
importantly, it’s light, strong and easy to machine.
form a natural protective oxide film that chemically
Aluminum is typically 2,5 times lighter than steel.
bonds to the surface of the metal. This film is
Once the lighter weight of aluminum is factored into
characterised by a powdery white or dull grey finish.
the equation, aluminum comes out on top with a
Unlike rust, the oxide layer will not flake off, however,
superior strength-to-weight ratio. It’s also more
this natural film is so thin (± 3nm ) that it will easily wear
malleable than steel, this makes it relatively easy to form
off. Therefore, for an increased corrosion resistance
while either cold or hot and is ideally suited for extrusion
aluminum is often anodised to give an oxide layer of
of complex shapes.
5 to 15µm.
It’s essential to note that aluminum in its pure form, is a highly reactive metal. Technically, pure aluminium dissolves when exposed to water. Often, alloying elements are added to achieve different properties, classified by their grade as listed in the table below.
Grade
Primary Alloying Element
Common uses
1000 Series
99% pure aluminium
Electric conductors
2000 series
Copper
Aircrafts
3000 series
Manganese
Roofing, siding
4000 series
Silicon
Weld fillers, brazing
5000 series
Magnesium
Marine applications
6000 series
Magnesium and silicon
Structural shapes, pipe
7000 series
Zinc
Aircrafts
Metals _ 47
STEEL = IRON + CARBON
WELDED STEEL BENCH FRAMES/ Quality inspection upon galvanizing
48
HOT ROLLED STEEL PROFILES / typical metal stock shelf
Carbon Steel Carbon steel, regular steel, plain steel, or simply just
Carbon steel is often divided into two main categories:
‘steel’ all refer to steel which is not stainless. Steel is
low-carbon steel and high-carbon steel. As the carbon
mostly composed of iron and a small amount of carbon
content percentage rises, steel has the ability to become
(0.05 - 2.1 %), two relatively affordable elements, that
harder and stronger through heat treating.
when combined, create a strong, easy to machine and easy to weld material. Steel is much stronger than iron in the domains of yield and tensile strength, but it’s also significantly tougher. This makes carbon steel the go to material for many industries.
Steel comes in many different shapes and sizes, stretch metal, perforated metal, wire mesh, ... The way steel is shaped, hot rolled or cold rolled, also has an affect on the strength and corrosion resistance. Cold-rolled steel, recognized by its smoother and more polished finish,
Exposed to a corrosive environment, carbon steel will
has a finer grain structure compared to hot-rolled steel.
rust while expanding approximately 2 to 6 times the
As a result, cold-rolled steel can have better corrosion
volume of the original steel and losing all strength in the
resistance, as the finer grain structure reduces the
process. Therefore, carbon steel is only considered a
likelihood of intergranular corrosion, which typically
durable material for outdoors when treated with the right
occurs along the grain boundaries.
protective coating! A more detailed explanation of corrosion and protective coatings will be provided in the upcoming chapters.
Metals _ 49
Stainless Steel (≠ stainfree steel) Stainless steel is a highly alloyed, low-carbon steel
For outdoor design, the most commonly used type of
with a high chromium content (>11%). Chromium is the
stainless steel is austenitic stainless steel, particularly
key element that makes it rust-resistant. The chromium
grades 304 and 316. These are ideal for outdoor
reacts to form a passive oxide layer on the metal’s
environments due to their excellent corrosion resistance,
surface, slowing further oxidation and providing a self-
high weldability, and durability.
healing quality, which helps resist corrosion. But as the name implies, stainless steel does not mean stainfree steel. So don’t be fooled, even stainless steel can rust, this is called “tea staining”. Tea staining is most common in areas that are near a marine
Grade 304 is the most common, offering good general corrosion resistance and is used in many outdoor applications like architectural details, railings, and furniture.
environment. Other probable causes of staining are iron
Grade 316 is similar but includes molybdenum, which
contamination, unclean welding or chemicals such as
provides better resistance to pitting and crevice
Chlorine.
corrosion, especially in marine and chemical environments. This makes it an ideal choice for coastal landscapes, outdoor sculptures, or any design elements near saltwater. Despite its advantages, it’s important to remember that stainless steel, like any material, requires proper care to maintain its appearance and performance. Routine cleaning and protecting it from sources of heavy contamination will help preserve its longevity and keep your outdoor designs looking pristine for years to come.
DID YOU KNOW? Cars are typically made from steel due to its affordability, strength, and ease of forming into complex shapes. The only production cars made from stainless steel are the DeLorean DMC-12 and the Tesla Cybertruck, which feature angular designs made by bending.
50
WALT DISNEY CONCERT HALL WITH STAINLESS STEEL CLADDING/ Los Angeles
Metals _ 51
The war against Corrosion! Corrosion is the biggest enemy of metal products and
The most obvious way of limiting corrosion is by
structures. The global cost of corrosion is estimated
removing the corrosive environment. Although the
to be US$2.5 trillion, which is equivalent to 3.4% of the
environment is often something we have no control over,
global GDP (2013).24
there are some premeasures we can take to limit the
Corrosion is a serious issue as it disrupts industrial ecosystems worldwide. Corroded products are often discarded, and corrosion by-products, such as rust, can contaminate water bodies.
contact. Minimize contact with water and humidity by proper outdoor design and/or a protective coating. It’s important to note that not all coatings are created equal. Even though different coatings may appear identical on the surface, what lies beneath can vary drastically in quality. The following is a brief overview of common types of corrosion, pretreatment and coating methods.
Design considerations for preventing corrosion: Material, coating, and pretreatment selection are crucial. Avoid completely flat surfaces or incorporate drainage holes. Minimize small crevices and sharp edges, as they can trap water. Ensure adequate ventilation to reduce humidity in enclosed areas.
52
Drainage holes in tabletop and seat help with good water evacuation
VIRUS PICNIC TABLE / Powdercoated stainless steel
Metals _ 53
Full welds all around prevents crevice corrosion
AMAI TABLE / Powdercoated stainless steel
54
50 Shades of corrosion There are many different forms of corrosion, some of the common ones are explained below. The purity or composition of the metal, crystal defects, grain structure, deformation, etc. all have an impact on the corrosion resistance of a metal. It’s therefore key to choose the right metal, pretreatment and coating required for the application. Uniform corrosion
Galvanic corrosion
Uniform corrosion is considered an even attack across
Galvanic corrosion is the degradation of one metal
the surface of a material and is the most common type
near a joint or juncture that occurs when two
of corrosion. This type of corrosion typically occurs over
electrochemically dissimilar metals are in electrical
relatively large areas of a material’s surface.
contact. Choosing metals that are as close together on
25
Pitting corrosion Pitting is one of the most destructive types of corrosion caused by a local break or damage to the protective oxide film or a protective coating. Its a localized form of corrosion, in which a local point forms a small corrosion
the galvanic series helps to reduce the risk of galvanic corrosion. For example, aluminium and zinc work well together, but aluminum and stainless steel have an increased risk of galvanic corrosion. Salt corrosion
cell with the surrounding normal surface. Once a pit
Salt accelerates corrosion because it enhances
has initiated, it grows into a “hole” or “cavity” typically
electrical conductivity in water, allowing current to
penetrate from the surface downward in a vertical
flow more easily. Since rust formation depends on the
direction.
movement of electrons, iron rusts more quickly in salt
Crevice corrosion Crevice corrosion is also a localized form of corrosion and usually results from a stagnant micro-environment. Crevice corrosion occurs in shielded areas such as those under washers, bolt heads, gaskets, gaps at incomplete welds, etc. These smaller areas allow for a corrosive agent to enter but do not allow enough circulation within, depleting the oxygen content neccessary for passivation to happen.
water than in fresh water. 26 Additionally, salt is hygroscopic—it attracts water. By drawing moisture from the environment, salt speeds up the oxidation process. As a result, salt water corrodes metal up to five times faster than fresh water, and salty, humid ocean air can cause metal to corrode up to ten times faster than air with normal humidity. Salt Spray Testing is a method used to evaluate corrosion resistance by exposing materials to a controlled salt mist, simulating harsh environmental conditions.
Metals _ 55
Electropolishing metals helps resist corrosion by minimizing the microscopic surface features that come into contact with the corrosive environment.
INUMBRA PARASOL / Electropolished stainless steel
56
Surface treatments Surface treatments are used to clean parts, improve corrosion resistance, adhesion for coatings, aesthetics, etc. Some common surface treatments for metals are the following. Pickling & Passivation
Electropolishing
Pickling uses a solution, which usually contains
Electropolishing does the opposite of shot blasting.
aggressive acid, as cleaning treatment for many
It’s an electrochemical process that removes material
coatings. Pickling removes impurities, such as grease,
from a metallic part, reducing the surface roughness
stains, inorganic contaminants, heat discoloration and
by levelling micro-peaks and valleys. It improves the
rust or scale. After pickling, the metal surface is active.
surface finish and corrosion resistance (as it reduces
Depending on the type of metal, it will immediately
the total surface area that comes in contact with the
corrode without further treatment.
corrosive environment.)27
In the case of stainless steel, a passive chromium oxide
Anodising
layer will naturally form after 24 -48 hours by exposure to the air. To prevent contamination pickup and to speed up the natural passivation after pickling, production lines often require a faster, chemical passivation
Anodising is a electrolytic process that converts metal surfaces into durable, decorative, corrosion-resistant finishes. This process is mainly used for aluminum, but
treatment.
also works on other nonferrous metals like magnesium
Blasting
oxide film of about 3nm, but anodizing increases this to
and titanium. Aluminum naturally forms a protective
Shot blasting is an alternative substrate cleaning method, it avoids caustic chemicals and it is ideal for large parts unsuitable for chemical dipping processes. It involves ‘blasting’ the substrate with various types of shot like sand, metal, soda ash, etc. Shot blasting removes mill scale, rust buildup, oils & dirt, weld spatter, etc. and creates a surface profile that enhances coating adhesion. The choice of shot depends on the substrate being prepared.
a much thicker layer, enhancing corrosion resistance. Conversion coating Conversion coatings react with the surface to create complex films via dipping, spraying, or brushing, providing corrosion protection and enhancing primer adhesion. Chromate and chromate-phosphate coatings have been effective in preventing corrosion of aluminum alloys for decades, but their use is limited due to carcinogenic effects, prompting research for alternatives.
Cleaning -> Pickling -> Conversion coating -> Metallic / Organic coating Example of a pretreatment process for steel
Metals _ 57
Metallic coatings All coatings are susceptible to damage from scratching
Galvanizing methods are broadly classified into two
or chipping, which can expose the bare metal beneath.
categories: hot galvanizing and cold galvanizing. In
Once the underlying metal is exposed, corrosion can
general, hot galvanized coatings have a much better
begin, leading to adhesion loss and the formation of
metallurgical bond to the base metal, because they
growing blisters. This issue is particularly severe with
create a layer of zinc alloy.28 The thickness and coverage
regular steel, as it lacks inherent protective properties.
of the galvanizing layer can also indicate its protective
Metallic zinc coatings, commonly referred to as galvanizing, provides an effective way to protect iron or steel from corrosion. These types of coatings
properties. The following section will provide a more detailed explanation of some of the most common galvanizing methods.
form a protective barrier that seals the metal from environmental exposure. Even if the coating is scratched and the underlying iron is exposed, the surrounding zinc will corrode first, producing protective precipitates that cover the exposed area. This self-healing effect, known as sacrificial anodes or cathodic protection, prevents further damage.
DID YOU KNOW? Another example of cathodic protection is used on boats with steel hulls. This steel is protected by acting as a cathode, while a cheap and easy to replace zinc bloc performs as a sacrificial anode.
58
ZINC as a gardian angel
HOPPER FRAME / Hot-dip galvanized steel
Metals _ 59
Hot-dip galvanizing With Hot-dip galvanization, the zinc layer is applied
Hot-dip galvanization is primarily used in industrial
by immersing the metal in a bath of molten zinc at a
applications (stairs, railings, fences and other
temperature of around 450°C. The process of hot-dip
constructions) because of its exceptional durability. For
galvanizing results in a metallurgical bond between the
example, research has shown that galvanised steel used
steel and zinc, with a series of distinct iron-zinc alloys
to build bridges would last longer than the concrete
that protects both the out and inside of a part.
structures along our roads: up to seventy years in the
Good quality hot-dip galvanization requires a suitable
wind and rain.
type of steel that is thoroughly cleaned. Typically, the
The galvanisation process used in many outdoor
steel is chemically cleaned to remove all oils, greases,
products is so sustainable that it even received the
soil, mill scale, and oxides. Surface preparation is
Cradle2Cradle certificate from the Cradle to Cradle
critical as zinc will not react with unclean steel.
Products Innovation Institute (San Francisco – USA) from its auditor ‘EPEA’ in Hamburg. Cradle-to-Cradle (C2C) describes the idea of thinking in complete product cycles and thus ultimately preventing any environmentally harmful waste from being produced at all, with materials passing through a cycle as they do in nature. However, the thermal application of the zinc layer is a
The undefeated world champion of coatings
process that consumes a lot of energy. The product’s incredibly long lifespan amply compensates for that. What is more, the steel structure is perfectly recyclable. So after all, it is a very raw, industrial technique.29
(with some personality issues)
60
HOPPER LEG / Hot-dip galvanized steel
Hot-dip galvanized parts can easily be identified by the crystallization patterning on the surface, which is also a good indicator for the quality of the coating. At first, galvanised products have a greyishblue sheen, over time, the look becomes more matt and neutral.
Metals _ 61
Sherardized steel Hot-dip galvanized steel
GARGANTUA / Legg connection
62
Electroplating
Sherardizing
Electroplating uses electrolysis to cover iron parts in a
Sherardizing also called vapor galvanizing or dry
very thin layer of another metal about 5-25 micrometers
galvanizing is a cementation process. It is a strong
thick. In the most corrosive environments, zinc plating
coating and provides good abrasion resistance, used
alone will probably not be sufficient. It is suggested to
in high temperature conditions. It involves heating up a
always combine zinc plating with an organic coating
steel part to a very high temperature. It is then put into a
for outdoor applications. Electroplating provides good
rotating drum which also contains zinc dust. The steel is
coverage, although it does not reach the insides of
then rolled in the drum full of zinc at a high temperature
hollow parts like tubes.
where the zinc will then evaporate and diffuse, bonding to the steel and filling in very small crevices.
Thermal spraying
Usually used for smaller parts nuts, bolts, screws,
Also called metallization, is the process of applying
spanners, etc. Applicable for base metal like steel.
a thin metallic coating to a substrate with a special technical gun. The gun is heated either electronically or using a flame, to melt the zinc upon spraying it onto the substrate. Because the substrate remains cooler than with hot-dip galvanization, there is virtually no risk of damage or distortion of the substrate. Thermal spraying can also be done with aluminium (TSA-coating) or a combination of the two in order to provide extra chemical resistance, lower cost than pure zinc, etc.
Typical zinc coating thickness on steel 140 µm
0 µm
Hot-dip galvanizing Shot blasting + Hot-dip galvanizing Zinc spraying Zinc electroplating Sherardizing Zinc rich paints
Pure zinc Zinc alloy layers Dispersed zinc pigment
Metals _ 63
Organic coatings The term “organic” refers to coatings that are primarily composed of carbon-based compounds, typically derived from natural or synthetic polymers, resins, or oils. Organic coatings are generally the last step in the process as they mostly have an aesthetic function. They can also provide some corrosion protection, however, it can be difficult to protect the inside of tubes or hard to reach corners. Corners and bends are the weakest parts of a coating because they naturally receive less coverage. If underlying corrosion occurs, this can cause the resin and pigment particles to lose adhesion, leading to the formation of ever growing blisters. In the case of steel, organic coatings and metallic coatings can also be combined. This is called a duplex coating combining the best of both techniques. The protective properties of a galvanised coating with the aesthetics of an organic coating.
Liquid coating
E-coating
Liquid coating is simply another term for applying paint
Electrophoretic Painting is a high-tech process
in liquid form, which dries to a solid finish. Because
developed over the last fifty years for applying anti-
this method doesn’t require heating, it’s commonly
corrosive coatings to steel car bodies. In this process,
used for large structures, bridges, and buildings where
coating materials (resins, pigments, additives) are
deconstruction is impractical. However, due to limited
dispersed in a water bath. Parts are immersed in this
layer thickness and adhesion, wet coatings need regular
solution and an electrical current is applied, using the
reapplication to protect against corrosion.
parts as an electrode. This makes the resin insoluble in
Liquid coatings consist of a liquid carrier (water-based or solvent-based) and solids, which remain after drying. The solids include resins for toughness, pigments for color, and additives for properties like UV protection and rust inhibition. Solids can be acrylic, enamel, or urethanes. Some liquid coatings cure through chemical reactions, notably in two-component (2K) coatings systems with a curing chemical component.30
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water, causing it to adhere to the parts’ surfaces. The electrical current ensures a consistent coating thickness. The coated parts are then removed and cured by baking to harden the coating. E-coating efficiently covers all surfaces, even complex shapes, with nearly 100% material utilization, resulting in lower unit costs and high-quality production.31
DID YOU KNOW? The Golden Gate Bridge is a constant painting canvas to protect the steel from corrosion. It’s a never-ending labor of love, as workers battle the elements.
GOLDEN GATE BRIDGE / Painted Carbon steel
Metals _ 65
MEASURING COATING THICKNESS / Powder coated stainless steel
66
Powder coating Powder coating is a dry finishing process where an
For outdoor use, a single layer of polyester or epoxy
electrically charged powder adheres to metal surfaces,
coating on reactive metals is insufficient, as the
then bakes in a curing oven for a smooth, durable finish.
elements can still penetrate the coating and attack
It’s tougher than traditional wet paint, offering better
the surface beneath. It is only when these coatings are
resistance to chipping, scratching, and wear due to
combined that they offer solid protection against the
thermal bonding. Because the particles size in most
outdoors. Alternatively, pretreatments like zinc-coating
powders is 30–50 µm, the coating should exceed at least
or anodizing can be applied to protect the base metal.
50 µm in thickness for effective protection. Applying
You can go even further for some components, using
too much powder can lead to uneven textures, improper
stainless steel as the foundation before applying a
curing, and compromised durability, causing issues like
coating. This is just one example of how higher quality
chipping, peeling, or cracking.
comes at a higher cost to meet outdoor durability
There are many types of powders on the market, the most commonly used are: Epoxy is considered the best in terms of corrosion and chemical resistance. It has excellent surface wetting
standards. Unfortunately, these added precautions are almost invisible at the surface level. The real benefits become evident only after the typical warranty period expires. Extremis products are designed to last far beyond that.
and adhesion to substrates. However, epoxy will not withstand exposure to UV light, the color will fade and the surface will chalk fairly quickly. This is why for outdoor use, epoxy coatings are only used as a primer. Providing additional protection from corrosion beneath a polyester topcoat. Polyester coatings are widely used because they provide excellent value and offer great impact, mechanical, and chemical resistance. Even though they cure at a low temperature, they exhibit high heat resistance. Polyester coatings also provide superior UV resistance, making them suitable for some outdoor applications.
Metals _ 67
Metal recycling
Unlike some materials like plastics or wood, metals are
Non-ferrous metals (like aluminum) are much easier to
permanent materials that can be recycled again and
recycle than steel. few materials are as easily recycled
again with no loss of quality. This makes them ideal for
as aluminium. It requires only 5% of the energy needed
a circular economy. However, recycling metals does
to produce the initial primary metal to recycle it. In
require a significant amount of energy, especially to
fact, 75% of all aluminum ever extracted is still in use.32
melt and process them into new products.
However, the extraction of aluminum is extremely energy
The production of ferrous metals (such as steel and
intensive.
iron) is particularly energy-intensive because they need
Carbon steel is an environmentally friendly material, as it
to be heated to very high temperatures for melting and
is easily recyclable. It is also energy-efficient to produce,
reshaping. For example, the melting point of steel is
as it requires less energy than other metals such as
nearly double that of aluminum.
aluminium.
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GALVANIZING STEEL TABLE LEGS / Extremis production facility
Metals can be recycled again and again with no loss of quality
Metals _ 69
Metal maintenance Some metals require more maintanance than other, but all metals will benefit from regular care. Without it, dirt and corrosives like salt, acids, small iron particles can accumulate and cause damage. Whenever possible, store metals in dry, temperate conditions, as extreme heat, moisture, or exposure to chemicals can accelerate corrosion or degradation.
Galvanized steel
While the surface may naturally develop scratches over
Galvanized steel is almost maintenance free, making
movement of rough or uneven objects over the material.
them ideal for public or semi-public spaces. However,
Most stains can be cleaned using stainless steel-specific
sometimes, white rust on galvanized steel can occur as
cleaners. When cleaning, always use non-ferrous tools—
a result of corrosion caused by moisture and improper
never use rust-prone items such as ferrous sponges,
handling or storage. While it doesn’t usually cause
scrapers, or steel wool, as these can damage the
severe damage, it can lead to the gradual deterioration
surface.
of the zinc coating. Preventing its formation through proper cleaning is key to maintaining the protective qualities of galvanized steel. Small damage can be touched up with zinc spray. If the zinc coating is in really bad condition, consider re-galvanizing the steel to restore its corrosion resistance before rust damage occurs.
Stainless steel Stainless steel is highly resistant to corrosion but should still be protected from salt exposure. Surface rust should be removed immediately to prevent damage.
70
time, major scratches can be minimized by avoiding the
Coated metals Use a mild detergent diluted in water. Avoid harsh or abrasive cleaners that can damage the coating.Also avoid the impact of sharp objects that can damage the coating. Scratches or dents can be repaired with a paint touch up pen. However this only camouflages the scratches without removing them.
HOPPER PICNIC/ Cleaning the powder coated legs with Extremis multicleaner
Metals _ 71
Textiles Textiles have been identified as the catalyst of technological changes. Their importance during the industrial revolution cannot be overstated. The textile industry was also the first to use modern production methods. In order to meet the demand for cloth and clothing of the ever growing population. Upholstered furniture, cushions, blankets, shades, carpets, etc. are what gives outdoor design good comfort and cosiness. This is done by gluing, stitching or welding different pieces of textile and/or foam together into a final product. Textiles can be quite complex as there are many aspects to it, all having a big impact on the final quality of the product.
72
Textiles _ 73
Introduction to textiles Textile is an umbrella term that includes various fiber-
Textiles are divided into two groups: consumer textiles
based materials, such as yarns, filaments, threads,
for domestic purposes and technical textiles. In
different fabric types, etc. At first, the word ‘textiles’ only
consumer textiles, aesthetics and comfort are the most
referred to woven fabrics. However, weaving is not the
important factors, while in technical textiles, functional
only manufacturing method, and many other methods
properties are the priority. Geotextiles, industrial textiles,
were later developed to form textile structures based
medical textiles, and many other areas are examples of
on their intended use. Knitting and non-woven are other
technical textiles, whereas clothing and furnishings are
popular types of textile manufacturing.
examples of consumer textiles.
Fibers Yarn Non-Woven
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Complex Yarn
Woven
Knitted
A fiber is the smallest component of a textile, it
After manufacturing, fabrics undergo various processing
determines the base properties of the textile, strength
and finishing techniques to enhance their value.
and stretchability, UV resistance, fire resistance, etc.
Methods such as washing, dyeing, steam treatment,
The sources of fibers may be natural, synthetic, or both.
coating, film application, lamination, linings, backings,
For non-woven fabric, the fibers are directly transformed into a fabric by mechanical, thermal or chemical processes. Most common example is felt, where fibers like wool or acrylic are bonded together as a result of the inherent friction (entanglement) from one to another.
etc. are applied to textiles. These post-processing treatments improve properties such as aesthetics, strength, abrasion resistance, water resistance, mold resistance, waterproofing, water repellency, fire retardancy, lightfastness, etc.
Yet, unless densified or reinforced by a backing, nonwoven fabrics often lack sufficient strength compared to woven fabrics.
Coating
For woven fabrics, the fibers are typically spun into a simple yarn, a long continuous length of interlocked fibres. Multiple yarns can be combined in different ways
Fabric
to create a complex-yarn.33 Yarns are then used to make different kinds of fabric by weaving or knitting. Most
Liner/interliner
commenly this is done in 2D to create a continuious sheet of fabric at a specific width. However, it is also
Backing
possible to structure yarns directly in 3D (Think about braiding, 3D knitting, etc.).
Textile fibres Natural
Synthetic
Animal fibres
Vegetable vibres
Inorganic/Mineral
Wool, Cashmere, Silk, ...
Cotton, Flax, Hemp, Jute, Sisal, ...
Glass, Carbon, Metallic, Stone
Organic /Polymer Acrylic, Polyester, Nylon, Poly-vinyl, Poly-urethanes, Poly-olefins, Rubber
Textiles _ 75
Three must-know fabrics Most outdoor fabrics on the market will be made from synthetic organic/polymer fibres because they tend to wear better than natural fibers and are more naturally resistant to moisture. Here we will dive a little deeper into three common fabrics used for outdoor architecture and furniture: Polypropylene, Polyester and Acrylic. The quality of a fabric depends on many different factors like weight (weight/area used to define the thickness of the fabric), fabric structure, chemical treatments, manufacturer, etc. Yet, at the core, many characteristics are defined by the choice of the base material.
Polypropylene (PP) Polypropylene is the chemical name given to the textile we know as olefin. Olefin fiber is a synthetic fiber made from a polyolefin, a byproduct of refining petroleum. Olefin fabric was developed from a form of polypropylene that came about in the 1930s. Since then, olefin fabric has become a popular choice in outdoor apparel and outdoor furniture upholstery due to its water-repellent properties and lightweight composition. One of the most important properties of olefin is its strength as it keeps its strength in wet and dry conditions and is very resilient. It’s also fire, and chemical resistant, colorfast and comfort, its resistance to mildew, abrasion, and sunlight. Olefin fibers have low moisture absorption, but they can wick moisture and dry quickly. Consequently, Olefin fibers do not dye well, but are very stain resistant without the use of stain treatment baths. POLYPROPYLENE YARN / Panigiri Byos
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Polyester (PES) Polyester and polyester-blend is a tough, versatile fabric that is cost effective. Polyester works well outside because it is resistant to stretching, abrasion - it’s also lightweight and flexible. Polyester is water-resistant, however, it’s not waterproof unless it’s coated with special materials. Polyester fabrics require a PFC chemical finish for stain resistance, this way they can resist mold, mildew, and surface stains. Polyester is usually batch-dyed, therefore, polyester fabrics on average will have a lightfastness score no higher than 1000 hours. Solution-dyed polyester is especially great for outdoor use - it has exceptional UV/sun resistance and wear properties. Not to mention, solution-dyed fabrics are much better for the environment (less water waste is used during production). HI-TECH POLYESTER SHADE / Inumbra parasol
Acrylic Acrylic fabrics are made from acrylic fibers. Acrylic along with Olefin is extremely resistant to fading from the sun. Excellent lightfastness. Acrylic is extremely easy to stain when not treated with a stain treatment bath, it combines the best of fade-resistance with mold- and mildew-resistant properties. These properties make acrylic upholstery ideal for humid environments, poolside lounging, and sun-loving patio spaces. Solution-dyed acrylics were made famous by outdoor fabric brands like Sunbrella®. It’s typically on the higher end of the price-range, but well worth it, since it lasts as long as 5 to 10 years.
SUNBRELLA® ACRYLIC / Walrus cushions and blanket
Textiles _ 77
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Textile finishes Textile dyeing Batch dyeing refers to fabrics that are woven white and
Solution dyeing diverts from traditional wet processing.
then dyed in drums to its desired color. This process is
Pigment is added to the molten plastic before making
great for obtaining mass amounts of colored fabrics but
the fiber. Since the yarn is created in a specific color
these fabrics are very receptacle to staining because
(versus first being produced and then dyed), the
of the mass about of dye sites in polyester fiber. These
color is confined within the yarn. The color becomes
fabrics tend to look great at first but become stained as
intrinsic to the fibers, so the process often yields
the treatment wears off.
stronger fibers than batch dyeing, which weakens and
34
damages the fiber’s integrity. Yet, not all solution-dyed fibers are created equal. Solution-dyed Acrylic can be atmospherically dyed, this means that the fiber has dye sites. The more dye sites a fiber has, the more stains can penetrate the fiber.
Batch Dying
Solution Dying
Textiles _ 79
Textile coating Textile coatings are often the last step in the process, when the fabric is already woven and a coating is applied either on one or both sides of the fabric. Coatings can be applied to make a fabric waterproof, improve strength, abrasion resistancy, UV resistancy, fire resistancy, etc. It is also possible to coat the yarns upon weaving, this will produce a mesh fabric that is not watertight but breathable. Thermo-fixing allows the yarns to fuse together after weaving to ensures dimensional stability. Nano-coating Are ultra-thin layers (measured on the nanoscale) that are built upon the fabric often by spraying. Some nanocoatings are polymers, either polymerized in-situ or prior to application. At the nanoscale, quantum physics comes into play, creating a hydrophobic effect that repels water and dirt. An industry definition is that a nano-coating is no more than 1–100 nanometers thick. Therefore, nano-coatings also wear off very quickly and have to be reaplied often. Historically, many nano-coatings have contained—or still contain—PFAS. However, growing environmental and health concerns have led to increasing pressure to reduce or eliminate their use. In response, the industry has been shifting
PVC-coating Is strong and durable, making it ideal for use in a variety of applications. They do not stretch and are resistant to many chemicals and weather conditions, making it ideal for outdoor use. PVC is relatively inexpensive to produce, making it a popular choice for many applications. However, the plasticizers used in soft PVC release toxic chemicals during production and its lifetime. PVC coated fabrics are also difficult to recycle because it is a complex material made up of several different components that are hard to separate. Silicone-coatings Have different properties compared to traditional PU and PVC coated fabrics. Silicone coatings do not use plasticizers, which are often found in PVC products. They also do not break down under UV light, deteriorate in cold temperatures, and maintains consistency and shape over time. It has been determined that there are no known health hazards associated with the use of silicone, hence the use in many food-grade applications. PU-coating
toward the development of non-PFAS alternatives for
Polyurethane coating have a plump feel, they are
nano-coatings.
elastic,and have a film feel on the surface. PU coated fabrics are mainly used in outdoor clothing and military industries,and are characterized by moisture permeability, wear resistance, wind resistance, and softness.
80
PVC TARPAULIN / Walrus sofa
When stitching a coated fabric, make sure to glue the seams to prevent water from entering.
Textiles _ 81
Textile maintenance Frequent washing can shorten the lifespan of fabrics by weakening fibers, fading colors, and gradually wearing away protective surface coatings. At the same time, leaving textiles dirty for too long can cause issues— organic matter such as rotting leaves or bird droppings may penetrate the fabric and lead to permanent stains. Therefore, it’s important to clean them immediately. The best strategy is to prevent dirt buildup in the first place. Store cushions and blankets indoors when not in use, and keep parasols closed or covered. If your furniture is placed near trees or dense vegetation, be aware that they will require more frequent care. This applies for all materials but textiles in particular.
Textile labeling Always consult the specific maintenance instructions from the manufacturer. These instructions are tailored to the materials and technologies used in your outdoor products. The requirements for labeling textiles vary from country to country. For instance, in the US, textile and apparel products must be labeled with fiber content, the manufacturer or dealer identity, and the care instructions. On the other hand, in the Europe Union (EU), Regulation (EU) No 1007/2001 states that textile labels should include either mandatory or voluntary information such as the country of origin and size.
82
HI-TECH POLYESTER SHADE & ACRYLIC FABRIC CUSHIONS / Garden
Close and cover parasols to shield them from debris and weather exposure.
Store cushions and blankets indoors when not in use.
Textiles _ 83
Sustainable design In 1987, the United Nations Brundtland Commission defined sustainability as “meeting the needs of the present without
compromising the ability of future generations to meet their own needs.” Nowadays, sustainability has become merely a buzzword used in every corporate marketing campaign, sometimes with little meaning behind. Why? Because the complexity of the topic makes it easy to fool people with greenwashing claims. This leaves the customer on its own in making a good assessment of a products sustainability. Sustainability is a progressive insight, we do not pretend to know the single truth about what’s really sustainable and what not. Yet we do know some things that certainly matter...
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Sustainable Design _ 85
STEEL MINING CRANE / Black Rocky Soil
86
The price of fast design Global Footprint Network calculated that Earth
According to Jonathan Chapman38, “The mess we are
Overshoot Day 2024 falls on August 1st. This marks the
in today is more likely to be a result of unsustainable
date when humanity’s demand for ecological resources
developments in the way we design, manufacture and
and services in a given year exceeds what Earth’s
consume objects in the modern world”. Even recycling
ecosystems can regenerate in that year. Material
does not break this cycle since as chapman point out
resource extraction could increase by almost 60% from
“consumers continue on, but do so, now, with recycled
2020 levels by 2060, from 100 to 160 billion tonnes – far
materials instead of virgin ones.” Recycling provides
exceeding what is required to meet essential human
consumers with a false sense of security – recycling
needs for everyone.
gives the consumer a cleaner conscious when it is time
35
36
A major issue is “fast furniture”, made in the last 10 to 15 years using low-quality materials. This furniture is often cheaper and considered disposable as it’s often hard to repair. The Environmental Protection Agency reported that Americans discarded over 12 million tons of furniture in 2018, with over 80% ending up in landfills and only 0.3% recycled. This means furniture accounts
to potentially throw away or replace an object. Chapman thinks that the current methods that designers employ has devolved into a treatment of non-sustainable ‘symptoms’. ‘Sustainable design’ regularly settles for a marginalized role in the product life cycle. As a designer, there is an imperative duty to work with a product’s entire life cycle in mind.
for about 6.6% of total landfill waste.37
Earth Overshoot Day 2024 falls on August 1st.
Jan.
Feb.
Mar.
Apr.
May.
Jun.
Jul.
Aug.
Sep.
Oct.
Nov.
Dec.
Sustainable Design _ 87
Impact in the long-run The chair with the least environmental impact is sitting
impacts, will reduce every year a piece of furniture is
on the floor. However, in order to add value for the user,
used. This demonstrates the significance of product
we have to use at least some resources and energy to
lifespan in creating lower environmental impacts.39
produce a real chair. The goal here should be to use
Good design aims for ways to reduce, rethink, and
these recourses as sustainably as possible. The focus on
reform consumption in the long run.
a long-term vision and avoiding overconsumption and waste underlines the importance of sustainable design for the present and future.
Total Life Cycle Impacts per year
Sarah Ingram of Arizona State University studied the environmental impact of durable design. The study found that if the lifetime of a chair doubles, the total life cycle impact per year halves. This important (though also somewhat intuitive) finding illustrates that resource depletion, as well as ecological and human health
15 year
88
30 year
45 year
60 year
Chair lifetime
“What makes a design sustainable? Not only the durability of the materials, but also the longevity of the idea.” Dirk Wynants
Durability
Longevity
Durability is the ability of a product to perform its
Longevity encompasses more than just the material
required function over a lengthy period of time.
properties of the product41. User behaviour, and broader
This includes the physical aspects of a design: the way a product or building is engineered, the materials used,
social and cultural trends play important roles in the product’s longevity.
and how the components are shaped and connected.
Will the importance of a design still be relevant to
Can the product remain functional, without requiring
the user and society in the future? Why do we readily
excessive maintenance or repair, when faced with the
dispose of some things, whereas we keep and maintain
challenges of normal operation over its lifetime?
others for years and years?
A parasol should not break in heavy winds, and a metal
A product that doesn’t have or quickly loses its reason
table should not rust shortly after purchase. Therefore,
of existance, because its a variation on an existing
we should develop and buy products that can withstand
product without offering anything extra, is in essence
‘wear and tear’ without breaking down. Designing
not a sustainable design. Regardless of whether it has
products for easy maintenance is also a big part to
been made out of the most durable materials. This often
ensure designs last well past their warranty period.
happens with products that follow a particular hype,
40
style or fashion trend, they quickly go ‘out of fashion’.
Sustainable Design _ 89
PICNIK / Design classic by Dirk Wynants & Xavier Lust for Extremis
A holistic approach The power of holistic design lies in considering every life-cycle stage, from raw materials to distribution, to minimize environmental impact. It is a more integrated approach to sustainability, transcending the superficial aspects of furniture or architectural design. At the start of a design process, you should consider certain aspects and make sacrifices that comply with timeless values. This is what makes design pieces endure and become heirlooms. Timeless designs are often known as such for a reason; their existence has demonstrated the ability to withstand the test of time and the judgment of the community across many different aspects of design. The right balance between functionality, aesthetics, circular design, and human connection.
90
Emotional value Cultural changes
Problem solving
Cultural changes
Design for people
Minimize environmental impact
Be inspired by social change, strive to promote social
Usefulness
Aesthetics
Biophilic
Maximize positive impact Functionality
interaction and harmony between people and their environment with outdoor designs that transcends the principles of form follows function.
Biophilic You boost human wellbeing with designs that are connected with nature through architecture and design. Key principles of biophilic design, creating healthy, quality and productive environments based on the patterns of nature.
Emotional value Products that are loved, liked, and trusted create a certain attachment that makes them stay relevant for longer. The best way to make a product last is to make it beautiful in every aspect. Aesthetically sustainable objects continuously add nourishment to human life, focusing on the psychological and sensuous bond between subject and object. They inspire both care and enjoyment, becoming a focal point of memories and experiences.
Functionality Be practical – fit the design to the purpose and what people need. Only develop an idea if it is both necessary and useful. User-centered design tries to optimize the product around how people can, want, or need to use the product, rather than forcing the users to change their behavior to accommodate the product. In essence, function always comes first and form follows.
Minimize environmental impact Closing the loop between the end of a product’s life and production is what supports a circular economy. In contrast to a linear economy, where products are made from virgin materials and disposed of in landfills or simply burned, discarded products are often viable goods that can be repaired but are tossed prematurely. Repair is often seen as difficult by consumers or deliberately made difficult by producers in order to sell more new products. Creating reusable, repairable, regenerable, and recyclable products that generate zero waste is paramount for sustainable design.
Sustainable Design _ 91
Conclusion Ultimately, everything begins with the design. A new product must earn its reason for being. Even though a product is created using the most sustainable methods possible, that alone is not enough. If a product fails to improve present and future lives more effectively than existing alternatives, then what is its purpose? A compelling WHY is identified even before the design process starts. Instead of thinking in terms of rooms, tables, chairs, the focus is on enhancing interactions among people while addressing the evolving needs of society. Rather than simply making products, the aim is to create “tools for togetherness”.
When designing or buying outdoor design, consider this: Start with a purpose—create sustainable design that fulfills a clear need. Minimize environmental impact—good design aims for ways to reduce, rethink, and reform consumption in the long run. Incorporate biophilic design—moreover in the E-guide to Biophilic design
92
AMAI TABLE / Design by Dirk Wynants for Extremis
Conclusion _ 93
References
94
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41
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References _ 95
Pictures All images, infographics and designs are considered the intellectual property of Extremis unless mentioned here below:
ICONS
96
downloaded from The Noun Project
COPPER PATINA / Statue of liberty in New York
by Victor Muñoz downloaded from Pexel
TREE ANALYSIS AND RESEARCH / by forestry worker
by Toa55 from Shutterstock
GOLDEN GATE BRIDGE / Painted Carbon steel
by Wendy Wei downloaded from Pexels
EIFFEL TOWER PARIS / made from Wrought Iron
by Kim Stewart downloaded from Unsplash
HOT ROLLED STEEL PROFILES / metal stock shelf
by Rodho downloaded from Shutterstock
WALT DISNEY CONCERT HALL / Los Angeles
by Tobias Keller downloaded from Unsplash
STEEL MINING CRANE/ Black Rocky Soil
by Pixabay downloaded from Pexels
References _ 97
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