Yes, from animal hides, almost any animal but primarily from cattle
hides. This is simply because of the abundance of cattle hides due to
the enormous world wide consumption of beef and subsequent tanning of
hides for leather. The trimmed hide pieces (too small or irregular
shapes to provide useable leather) are shipped to the hide glue plant.
The glue manufacturing process is basically the following:
wash to remove dirt
The process can lend itself to "home brewing" but it is messy and the aroma is found by some to be less than exciting! Your best bet is to buy the finished product from a reliable supplier.
Hide glue is a protein derived from the simple hydrolysis of collagen which is a principal protein constituent of animal hides. Collagen, hide glue and gelatin are very closely related as to protein and chemical composition. An approximate chemical composition for glue is:
The molecular weight of hide glue has a wide range from 20,000 - 250,000. The higher the gel strength, the higher the molecular weight.