a substance used to adhere one thing to another
Different ingredients to make glue are available in different parts of the world. The process of making a good adhesive is usually time-consuming, and involves a fire. Sometimes the glue did not have to be so strong because it was part of the process of lashing things together with sinew or cordage.
Many glues are also varnishes. They are used to coat items to make them waterproof. (Neandertals mixed glue with pigments to make moisture-proof paint.) People also prize the glossy appearance some glues bestow.
Resin glues are made from sap tapped from plants. Brewer’s pitch is the sap of the Pitch Pine (Pinus rigida), which is a water-resistant type of wood because of its resin content. When heated, it melts and can be spread around as a varnish. It was used to coat the inside of wooden mugs up until Civil War times in America.
“Animal glues” refer to preparations using various animal parts, usually connective tissues, to extract collagen and other proteins. Bone glue was made by boiling animal bones and teeth. Sinew and hide could be made into glue. Antler and horn were also sources of glue. Parts of cattle, horses, rabbits, and fish were known to be used. Sturgeon’s bladder glue was used in Asia by bowyers to make an especially strong bond.
Like resin glues, animal glues were stored in a dry pellet or crystal-like form. They had to be heated for use.
The modern air-dry white glue is generally made from milk. The proteins are milk caseins. Primitive people usually did not use air-dry preparations as adhesives because they lacked air-tight container technology.