Today continues our daily Merry Blogmas 2017 posts of short science-lite articles for Dec. 1 through Christmas.
Hide Glue and Other Collagen-Based Glues
Collagen is the principle protein in the bone, muscle and skin tissues of mammals and certain fish. It is made up of fibrous strands of polypeptides, which is the same as saying that collagen is made up of long mostly-straight chains of linked amino acids.
Collagen-based glues include those made from:
- animal hides
- animal hooves of animals
- fish skin
- air bladders from fish
- fish bones
Making Collagen-Based Glue
The chemical process for making collagen-based glue is to cook epidermal or skeletalmuscular
material down in water:
- The peptides bonds between the fibrous strands of collagen polymers break apart.
- The protein strands get disassociated in the watery goop.
- When water is removed from the goop, the strands kink and rebind (see diagram below).
- The re-gelled material is not as strong as the original tissue.
- It has the virtue that it can be dried as sheets or as solid granules.
- For use, it is rehydrated and it sets up as a glue by simply letting it dry out again.
- It has the virtue that it can be stored for forever if kept dry.
- It has the detraction that it can be destroyed by penetration of moisture after it has set.
The Varieties and Uses of Collagen-Based Glues
Collagen-based glue is one of the oldest types of glue known. Its use predates written history.
Depending on the species, age and type of tissue material being used to make collagen-based glue, there may or may not be other substances mixed in with the collagens.
- The purer the collagen content and the milder the cooking-down processes, whiter or clearer the glue will be.
- The purest rendered collagen glues are hoof gelatin and sturgeon isinglass.
- The better grades of collagen-based glue, like isinglass, were and still are superior glues for fine handcrafted woodworking projects like lute making and other musical instrument building.
- Rabbit-skin glue is still a preferred material for making grounds for laying gold leaf on paper, parchment and vellum.
I know historical reenactors and artists who make their own collagen-based glues. I’ll be honest and confess that when I want to use a collagen-based glue, I cheat and use Knox brand unflavored gelatin found at almost every grocery store in the USA.
Banner image of collagen strands by J. W. Schmidt, 2005, CC BY-SA 3.0 via WikiCommons