Design for Print.
Close up of four-colour (CMYK) halftone separation print.
2_3: Contents 4_5: Printing Methods 6_7: Flexography // Lithographic 8_9: Rotogravure // Screen Print 10_11: Colour Theory & Colour Modes 12_13: Colour Mode Examples 14_15: Print Finishes 16_17: Print Finish Examples 18: Bibliography
When designing for print there are many printing methods at your disposal. That said, the method that you choose to print with is normally determined by the job itself. Whether it be by volume, reproduction accuracy or speed there is a print method out there specifically designed to suit any print jobs needs.
Rotary printing uses a printing press in which the images to be printed (plates) are curved around a cylinder. Printing can be done on large number of different substrates, including paper, cardboard, plastic and foil. Substrates can be sheet feed or unwound on a continuous roll through the press to be printed and further modified if required (e.g. die cut, overprint varnished, embossed). Printing presses that use continuous rolls are sometimes referred to as ‘web presses’. Today, there are three main types of rotary presses; offset commonly known as offset lithography, rotogravure, and flexography. While all three types use cylinders to print, they vary in their process.
Generally used for short print runs, digital printing is the reproduction of digital images on a physical surface / substrate. Digital print differs from rotary printing in several ways: Because printing plates aren’t required every print can be different. An issue number, for example, can be added at the click of a button increasing by one unit per print. There are also less wasted chemicals and paper, because there is no need to bring the image ‘up to colour’ and check for registration and position. Inks used in digital print do not permeate the substrate, instead it forms a thin layer on the surface. Because there is less initial setup for digital print, it is useful for rapid prototyping, and cost effective for small print run
Screen printing is a printing technique that uses a woven mesh to support an ink-blocking stencil. The attached stencil forms open areas of mesh that transfer ink as a sharpedged image onto a substrate. The use of the woven screen allows complex stencils to be supported by the weave. The print process involves a roller or squeegee moving across the screen stencil, forcing ink past the threads of the woven mesh in the open areas, leaving a crisp image. This process has to be done for each colour separation (screen), building up the image colour by colour, typically CMYK (see pg. 10)
Pad printing is a process by which a 2-D image can be transferred onto a 3-D object. This is able to be done by using a process that involves an image being transferred from the printing plate via a silicone pad or stamp onto a substrate (the surface to be printed). Pad printing is used for printing on otherwise impossible products, such as stationary, electronics products, sports equipment, toys etc. The pad printing process can also be used to deposit functional materials such as conductive inks, adhesives, dyes and lubricants onto objects.
The flexographic print process begins with the manufacture of a flexographic plate, which is differs from plates made for the rotogravure and offset lithography print processes. Instead of a metal or polyester plate, a flexographic plate is rubber. This adds a more malleable quality to the plate and allows images to be printed on to substrate that have a flexible quality, typically foil, plastic, cellophane and metallic films.
As mentioned previously flexography is used for printing food packaging but is also widely used when printing labels, magazines, catalogues, newspapers and cheap paper back books.
Flexography was developed and is widely used for printing onto non-porous substrates required for various types of food packaging (it is also well suited for printing large areas of solid color). Due to this flexography is used for printing where quality is not the main objective. The price of flexo printing is therefore cheaper than that of Lithography but there is a compromise on print quality; photographic prints or full colour prints would not appear as good as they would through the lithographic process.
Offset Lithography or Litho for short, is a high volume, rapid printing process that produces constantly clean results. Offset litho presses are typically set up to print four colours, Cyan, Magenta, Yellow and Black (Key). The image to be printed is separated into these colours and a printing plate made for each. When the substrate is sent through the printer each ink/ plate is printed separately, building up colour to create a full colour image. This build up of colour is made by each colour separation plate being made up of halftone dots (see pg. 2). These dots are used to replicate the continuous photographic tones in the print process. Each process colour’s plate has a standard angle for the dots (black 45 degrees, magenta 75 degrees, yellow 90 degrees and cyan 105 degrees). Once all colours are printed these dots give the impression of a full colour image. Lithography works on the principle that oil and water don’t mix. The image area of each plate is treated with chemicals to make it attract
oil and repel water and the negative area treated with chemicals that do the opposite. The plate is then wrapped around a cylinder and oil based ink and water are funneled onto the plate. As the plate revolves the water cleans the negative area of the plate, whilst the ink remains clinging to the image. The plates used in litho printing vary depending on the size print run. Polyester is typically used for short run plates (1,000 – 30,000) but print quality is lost over time. Copper or aluminium plates last much longer and can be used for runs of up to 250,00. Lithography is extremely flexible and cost effective for small to medium print runs (1,000 – 50,000), there are a wide range of presses ranging from small sheet fed machines to large web (paper roll) fed machines. Typically most litho printers will run with 4 process colours but modern machines can run up to 6 colours (4 process – CMYK and 2 additional spot colours).
Rotogravure is the printing process used for printing high volume print runs at high speed. The engraving plates used in rotogravure last an incredibly long time before degrading making them perfect for consistent print quality on very long runs. The process involves making several plates (one for each colour separation) via engraving the text/image that is to be reproduced onto each plate. This plate is then wrapped around a cylinder, like in lithography. However, unlike litho printing this cylinder simply passes through an ink well. No water is used to clean the negative of the plate; instead the plate cylinder passes a doctor blade that removes all the ink from the surface of the cylinder. The ink is then released onto the substrate when passed under pressure from the impression cylinder. This action of doctor blade and impression cylinder ensures that the engraved wells of ink on the surface of the plate are evenly filled to ensure a greater print quality.
Often web fed, rotogravure is very good at printing on cheap substrate. This use of cheap substrate and its ability to produce large quantities at rapid speed make it perfect for printing publications such as national newspapers.
Screen print is a printing process by which ink is squeezed through a screen onto a sheet of substrate to make a print. Like most other methods of printing the first stage of this process it to make colour separations that allow you to push the inks through separate screens, building up to create a full colour image when they are printed on top of one another (similar to lithography). The method of preparing and making a stencil screen is as follows: The original image (colour separation) is created on a transparent overlay such as acetate or tracing paper. The image may be drawn or painted directly on the overlay, photocopied, or printed with a inkjet or laser printer, as long as the areas to be inked are opaque (usually black ink). Next a screen must be selected. There are several different mesh counts that can be used depending on the detail of the design or the substrate to be printed onto (e.g. paper or fabric specific screens).
Once a screen is selected, it is coated with light sensitive emulsion and left to dry in a darkened room. Once dry, the screen is ready to be exposed. To expose the screen the overlay is placed underneath the emulsion-coated screen, and then exposed with a light source containing ultraviolet light. The UV light passes through the clear areas of the overlay and creates a polymerization (hardening) of the emulsion. After exposing the screen is washed off thoroughly. The areas of emulsion that were not exposed to light (black on the printed overlay) dissolve and wash away, leaving a negative stencil of the image on the mesh through which ink can be squeezed with a squeegee. Screen printing can either be done hand done for small scale print runs or machine automated for larger print runs. Screen printing is popular because each print is individual, no two are the same. It’s hand rendered appearance is also desirable.
Subtractive colour model.
When preparing a job for print it is important to consider the colour mode you use. This is part of colour management â€“ the process that governs how colour is translated from one piece of equipment in the printing process to another. Colour management is needed to ensure accurate and predictable colour reproduction because each device responds to or produces colour differently.
Process colour halftone separation.
The CMYK color model, sometimes referred to as process color, is a subtractive color model. Used as a basis for color printing it can also be used to describe the printing process itself. CMYK refers to the four inks used in most color printing: cyan, magenta, yellow, and key black. The CMYK model works by partially or entirely masking certain colors on the typically white background. Such a model is called subtractive because inks â€™subtractâ€™ brightness from white.
Halftone dot angle of process colours.
With CMYK printing, halftoning allows for less than full saturation of the primary colors. Tiny dots of each primary color are printed in a dot pattern small enough that human beings perceive it as a solid color. Magenta printed with a 20% halftone, for example, produces a pink color, because the eye perceives the tiny magenta dots and the white paper between the dots as lighter and less saturated than the color of pure magenta ink. Without halftoning, the three primary process colors could be printed only as solid blocks of color, and therefore could produce only seven colors.
Print Theory & Colour Modes
Panton colour swatch book.
PANTONE AND SPOT COLOURS
Graphic designers use spot colours to ensure that a particular colour in a design will print accurately. This may be necessary if the colour is outside the range or gamut of possibilities of the four-colour CMYK process. Alternatively there may be a pressing need for a specific colour, such as for a specific corporate logo. Special colours and spot colours have a greater intensity and vibrancy as they print as a solid colour rather than one that is composed of halftone dots (CMYK). The pantone colour system has also developed to include fluorescent and metallic colours. Something the CMYK process colours cannot produce.
Monotone printing is printing where one colour is used. Instead of building up colours to create an image only one colour is printed. Tints of this one colour are then used to create highlights and shadows. Monotone printing is often used when there is a lack of budget for a project, as obviously one ink costs less than four. But with the progression of digital print technology digital print is becoming cheaper for short runs so today it is less of a problem.
Similar to monotone but as the name suggests two colors are used. Again this is a useful print technique if you have a tight budget. Highlights and lowlights are made not only by tints but colour selection. For example if you choose a light and dark colour they may work to your advantage. Specific Pantone or spot colours can be used and applied to a photographic image a useful technique when producing work with a limited pallet for a company that has corporate spot colours as part of their identity. Tritone and Quadtone work in the same was as mono and duotone but with the addition of one colour each time.
Print finishing encompasses a wide range of processes that can provide the final touches to a design once the substrate has been printed. Special print finishes can transform an ordinary looking piece into something much more arresting. Although finishes are applied post printing they should not be an afterthought, but rather considered during the planning stage of a project.
Die cutting is the process that uses a steel die to cut away or stamp out a specified part of a design. Normally used for decorative purposes it can also enhance the visual impact and performance of a piece. In addition to altering the shape of a design to enhance visuals, die cutting itself can also serve a functional purpose â€“ creating cutouts or windows so the user to see inside or through a publication. Die cutting can be done separately on a flatbed post printing or the die cutting can be integrated into the printing press itself.
Generally used for short print runs, digital Embossing is the act of stamping a design into a substrate. This create a three dimensional, raised pattern in the substrate and can be used in conjunction with ink or foils. It is normally used to create decorative or textured surfaces to provide emphasis on certain elements of a design. The opposite of embossing is debossing â€“ instead of a raised pattern being stamped into the design it is sunken into the substrate and as a result it is sometimes known as negative embossing. Generally, a thicker stock holds an emboss much better than thinner stocks and similarly to foil blocking embossing comes with a premium price due to the extra equipment needed.
The foil blocking process consists of a coloured foil being pressed onto a substrate via a heated die. This causes the foil to separate from its backing and stick to the substrate. Foil blocking can be combined with embossing to create multi dimensional, elegant prints. This is often called sculptured foil embossing. By its very nature foil blocking is a very expensive print process with sculptured foil embossing even more so due to the extra embossing die to be produced. That said it can be used to great effect to produce highquality, eye-catching results.
Varnishes are colourless coatings applied to a printed piece to protect it from scuffing, wear or smudging. However, varnishes can also be used to enhance the visual appearance of a design, or elements within it. Varnish can produce three main types of finish â€“ gloss, dull and satin. Gloss reflects back light and is frequently used to enhance photographs of specific graphic elements within a printed piece. Dull or matt varnishes are typically used on text heavy pages to diffuse light and prevent glare â€“ increasing readability. Satin varnish is the middle option between gloss and matt, providing some highlights without the flatness of matt. Varnishes are particularly successful when printed onto matt stocks to highlight particular elements of a design and imparting a different texture.
I hope this booklet has been useful in terms of learning about designing for print and print production itself. It is by no means a comprehensive guide to print. There are many more facets and nuances to print production that you would struggle to fit in a book let alone this booklet! The best way of learning these is to get your hands dirty and get designing for print. Thank you for your time. Ollie
The Production Manual – Ambrose & Harris (AVA Academia) Colour Management – J. Drew & S. Meyer (Rotovision) Experimental Layout – I. Noble & R. Bestley (Rotovision) Grids – Ambrose & Harris (AVA Academia) Print & Finish – Ambrose & Harris (AVA Academia)