Included here largely as
a matter of historical interest, Starch glues still are no longer often used in
the wood industry. They have been replaced by urea-resin adhesives in gluing
interior-type hardwood plywood and furniture. As the name implies, the
principal component of these adhesives is starch which may be obtained from a
variety of plants including corn, potatoes, rice and cassava. Vegetable glues
are ordinarily sold in powdered form and must be mixed with water. Other
chemicals such as alum may be added to improve their properties. These mixtures
are heated to prepare them for use--heating flour paste, for example, renders
the flour soluble. Vegetable glues are relatively inexpensive and have a
relatively long pot life. They set through loss of water, which may be quite slow,
so that glued assemblies must often remain clamped overnight.
