WALLPAPER STORIES The mill
manufacturers are launching new collections more frequently than ever.” Some consumers want luxury wallpapers, with the corresponding price tag, whereas others are looking for the cheapest possible products. “Different designs set different requirements for the printing technology to be used. Preferences and trends vary greatly between markets, and we have to be able to meet the needs of customers, professional decorators and consumers alike. For this reason Cresta, the brand for all our wallpaper base products, has a wide-ranging portfolio suitable for different printing technologies such as screen, flexo, gravure and digital printing, as well as for different hanging methods.” “In Kyro we manufacture both singlelayer wallpaper base and double-layer base that uses different pulp combinations. The base paper of the single-layer product mainly consists of mechanical pulp and is used for embossed and textured PVC-coated wallpapers. To produce peelable wallpapers, the base paper is produced with two layers consisting of different pulps – the back of mechanical pulp and the top of chemical pulp. To achieve good printability and light fastness, we have products with one, two or even three coated top layers.”
Haaranoja. “Fibre behaves in the same way when it absorbs moisture, for example from wallpaper glue. Therefore, irrespective of the type of wallpaper, the dimensional stability and wet-strength properties are of utmost importance. For this reason, all Cresta products are heavily stock sized.” For the growing paste-the-wall segment, nonwoven base is needed as the wallpapers must not expand once they have been hung. Metsä Board has developed two products designed for this purpose: Cresta NG2S and Cresta NGX. The wallpaper base for these products is made with two layers consisting of a mixture of chemical pulp and synthetic fibres to guarantee that the wallpaper doesn’t expand when pasted on the wall. “Cresta NG2S is triple-coated and strippable, and has been specially developed for flexo and gravure printed wall coverings. Cresta NGX is a double-layer, strippable non-woven wallpaper base that is coated on both sides. Specially developed for PVC coating and rotary screen printing, it has extremely high opacity and heat resistance. With the Cresta product range we are able to meet the needs of the paste-the-wall segment,” Haaranoja stresses. Apart from dimensional stability, properties like curl and fibre direction are very important as they influence the wallpaper’s behaviour when it’s being hung. The wallpaper must have good wet strength and be flat, even when the reverse side is covered with paste or makes contact with the pre-pasted wall.
FIBRES ARE LIKE HUMANS
“In a way, a cellulose fibre is like a human being – the more we eat and drink, the more we swell in our cross direction,” says
BAD OPACITY GIVES A BAD IMPRESSION
Everyone who has hung wallpaper knows that the last thing you want to happen is for the previous layer to be visible through the new one. This is where the opacity of the wallpaper base is critical.
“CONSISTENCY IS A CRITICAL PARAMETER. WALLPAPER ROLLS FROM DIFFERENT PRODUCTION BATCHES MUST HAVE THE SAME SHADE AND BRIGHTNESS.” – OLLI HAARANOJA
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Magazine special edition 1/2015