How is animal glue made from collagen?

Animal glue is produced through the hydrolysis of collagen, the primary structural protein found in the skin, bones, tendons, and connective tissues of mammals.123

In its natural state, collagen is insoluble in water due to its triple-helix structure. To convert it into glue, the collagen must be treated with hot water, acids, or alkalies. This process causes heat denaturation, which destroys the triple-helix structure and partially hydrolyzes the protein chains.143

The resulting product depends on the intensity of the processing:
* Gelatin: Produced when the starting material is pure and the conversion process is mild. This high-molecular-weight product is often used in food or photography.1
* Animal Glue: Produced through more vigorous processing. This material typically has a lower molecular weight and is less pure than gelatin, resulting in a darker color.1

Once processed, the unfolded peptide chains of the resulting material are capable of trapping large amounts of water, creating the adhesive properties traditionally used in woodworking and bookbinding.13