
Animal glue is an
adhesive that is created by prolonged boiling of animal
connective tissue
Connective tissue is one of the four primary types of animal tissue, along with epithelial tissue, muscle tissue, and nervous tissue. It develops from the mesenchyme derived from the mesoderm the middle embryonic germ layer. Connective tissue ...
in a process called
rendering.
In addition to being used as an adhesive it is used for
coating and
sizing
Sizing or size is a substance that is applied to, or incorporated into, other materials—especially papers and textiles—to act as a protective filler or glaze. Sizing is used in papermaking and textile manufacturing to change the absorption ...
, in decorative
composition ornaments, and as a
clarifying agent.
These
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respon ...
colloid glues are formed through
hydrolysis
Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile.
Biological hydrolysis ...
of the
collagen from skins, bones, tendons, and other tissues, similar to
gelatin. The word ''collagen'' itself derives from
Greek (), meaning 'glue'. These proteins form a molecular bond with the glued object. Conventionally,
keratin glues, while made from animal parts like horns and hooves, are not considered animal glues as they are not collagen glues.
Stereotypically, the animal in question is a
horse, and horses that are put down are often said to have been "sent to the glue factory". However, other animals are also used, including cattle,
rabbit
Rabbits, also known as bunnies or bunny rabbits, are small mammals in the family Leporidae (wh