Wallpaper paste
Wallpaper adhesive or wallpaper paste is a specific adhesive
An adhesive, or glue, is a mixture in a liquid or semi-liquid state that adheres or bonds items together. Adhesives may come from either natural or synthetic sources. The types of materials that can be bonded are vast but they are especially useful for bonding thin materials...

, based on modified starch
Modified starch
Modified starch, also called starch derivatives, are prepared by physically, enzymatically, or chemically treating native starch, thereby changing the properties of the starch. Modified starches are used in practically all starch applications, such as in food products as a thickening agent,...

 or methylcellulose
Methyl cellulose is a chemical compound derived from cellulose. It is a hydrophilic white powder in pure form and dissolves in cold water, forming a clear viscous solution or gel. It is sold under a variety of trade names and is used as a thickener and emulsifier in various food and cosmetic...

, used to fix wallpaper
Wallpaper is a kind of material used to cover and decorate the interior walls of homes, offices, and other buildings; it is one aspect of interior decoration. It is usually sold in rolls and is put onto a wall using wallpaper paste...

 to walls.

Wallpaper pastes have a typical shear thinning
Shear thinning
Shear thinning is an effect where a fluid's viscosity—the measure of a fluid's resistance to flow—decreases with an increasing rate of shear stress. Another name for a shear thinning fluid is a pseudoplastic. This property is found in certain complex solutions, such as lava, ketchup, whipped cream,...

Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...

 and a high wet adhesive tack. These properties are needed to slow down the penetration of the adhesive into the paper and wall, and give slow bonding speed which gives the wallpaper hanger time to hang the wallpaper correct to the wall.

The wallpaper adhesive is applied to the wallpaper to let the moisture of the adhesive soak into and penetrate the paper. The paper will thus expand before hanging rather than on the wall, which would cause vertical bubbles in each panel of wallpaper as the adhesive dried from the edges in. When using nonwoven or glassfibre
Glass-reinforced plastic
Fiberglass , is a fiber reinforced polymer made of a plastic matrix reinforced by fine fibers of glass. It is also known as GFK ....

wallpaper—paper that does not expand—the adhesive is applied to the wall instead.
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.