Starch glue or carbohydrate glue is based on vegetable starch.The paste is relatively weak and is used primarily for pasting paper and wallpaper, but it can also be used for lighter woodwork and is used in the USAfor gluing plywood. Potato flour paste and flour paste are starch glues.
Potato starch is dissolved in warm water and mixed to a porridge. The porridge is allowed to stand for 10 minutes so that the water is absorbed by the grains of starch and thickens. Afterwards cold water is added to make it easy to stir.The mixture is then boiled to thicken it more; water is added until a workable consistency is obtained. The glue must not be used until it is cold. If the paste has to stand for a time a little alum is added to prevent it turning sour. If hydrochloric acid is added to the potato starch, dextrine isformed, which gives a glue of afar higherdurability. Dextrine is also used in fillers containing gypsum.
Flour from wheat, maize or rye is used to make flour paste, which is stirred in warm water to a white sauce, adding water carefully so that the paste does not become lumpy.The mixture can also be sieved.This glue must be used cold, and it is a definite advantage to add alum. Paste from wheat flour is mostly used to stick paper and wallpaper. Rye four paste is a little stronger and is used for sticking paper on hessian, linoleum and wallpapers, and as a filler. Sago four is used for the gluing of wood. In commercial products, fungicides are often added.
An emulsion filler based on ryeflour is madefrom 1 part boiled linseed oil,1partof water and about 1 part chalk.This is gently mixed and allowed to stand for half an hour without being stirred. A pinch of rye flour is sprinkled on the mixture and thoroughly stirred in. More chalk, which acts as the filler, is added, until the mixture has the consistency of porridge. Pigments such as umberand ochre can be used to colour it.
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