How do I glue leather together naturally?

I'm trying to figure out how to mend tears and holes in leather without using any of the synthetic glue products and repair kits that are so popular. So far, I've found two ideas:

1 - leather book binding glue (gelatin based)
2 - animal hide glue

Those links are for DIY instructions, but I'm guessing these products can be purchased as well. Are there other natural glues and adhesives for leather? Does anyone have experience gluing leather with natural products? Has anyone tried some of the common homemade glues like flour and water on leather? I'd be interested in your experience.

When I did my third leather book, I made hide glue with gelatin powder, water, and a dash of cloves. The cloves are added to both book binding glue (made with wheat) to help prevent decomposition, so it seemed to make sense to add it to my hide glue.

The hide glue worked really well! It acts fast, especially the thicker it is. So it totally holds things together while you work, and also seemed to do a mighty fine job of sticking the leather to the cover. Here's a picture of mine when I first stuck the mixture on the woodstove to heat up:



It was really easy to make. Here's the recipe/ratio I used. This site has some spiffy info about wheat glue vs hide glue, as well as how straight gelatin glue vs normal hide glue worked.

I got the great spine definition with hide glue, too. I did use quite a bit, though, as just a little didn't seem to be enough:

Nicole, this is great! Your books look so professional.

Question - how do you think it would work on say, a patch over a hole for a leather jacket? Do you think it would dry too stiff? Or would it be acceptable?

From what I've read, isinglass is possibly the strongest natural adhesive. It was used for gluing together pieces of wood, horn, and sinew to make composite bows.

https://daily.jstor.org/isinglass-or-the-many-miracles-of-fish-glue/

Jordan, interesting. I did a little more searching and found a how-to here, How to Prepare Isinglass. If it's used on bows, I wonder how flexible it is after it dries.

Leigh Tate wrote:Nicole, this is great! Your books look so professional.

Question - how do you think it would work on say, a patch over a hole for a leather jacket? Do you think it would dry too stiff? Or would it be acceptable?

I folded a scrap of leather about 3 hours ago with hide glue. It's very flexible. It does not feel stiff at all. I mean, it's basically really thick jello. Jello is springy and bendable (think jello gigglers or gummy bears.) It sticks together quite well. I can pull my leather apart...but I also applied it to the suede side, so basically I'm just ripping out suede to separate it.

Nicole Alderman wrote:

Leigh Tate wrote:Nicole, this is great! Your books look so professional.

Question - how do you think it would work on say, a patch over a hole for a leather jacket? Do you think it would dry too stiff? Or would it be acceptable?

I folded a scrap of leather about 3 hours ago with hide glue. It's very flexible. It does not feel stiff at all. I mean, it's basically really thick jello. Jello is springy and bendable (think jello gigglers or gummy bears.) It sticks together quite well. I can pull my leather apart...but I also applied it to the suede side, so basically I'm just ripping out suede to separate it.

A couple cautions for using hide glue or gelatin on a jacket (gelatin is a purified form of hide glue) -- different hide glues have different amounts of flexibility. Rabbit hides make an excellent, flexible hide glue which is great for bookbinding; my bookbinding friends say that fish swim bladder hide glue is even better--a stronger glue with even more flexibility. Glues that are good for bookbinding are poor for joinery, where you don't want much movement. For furniture making, the hide glue granules/flakes you buy at the hardware store are preferable, and comes in a range of strengths, depending on your application. Foodsafe gelatin sold as such tends to be on the weaker end of hide glues, but works ok for low-stress applications, such as instruments. I know a few fine woodworkers and luthiers who use hide glue, and it is actually stronger than the wood around it in many cases. But the stronger it is, the more brittle it is. For binding leather, you'd want something much more like bookbinding glue and less like glue for making furniture.

The second, and perhaps more important, thing is that objects that have been hide glued must not ever come into contact with water! Water will liquefy the glue and leave you with a join full of goop, which is not what you want! If you'd only be wearing your jacket inside, this would be fine, but if there is a chance of wearing it out in the rain or snow, I'd take a different tactic.

For a waterproof, natural glue with some flexibility, you could try making cheese glue (it sounds weird, but I have used it and it's pretty good!).

Method for patching leather:
- Hold the tear closed. Cut a patch larger than the tear in all dimensions
- Use cheese glue to attach the patch to the wrong side of the fabric
- Once the glue is dry, use tunnel stitching to attach the patch to the coat; the stitches should not be visible on the outside

Best of luck!

M Broussard wrote:... objects that have been hide glued must not ever come into contact with water! Water will liquefy the glue and leave you with a join full of goop ...

That's exactly the other question! Especially because I'm particularly interested in repairing leather clothing and shoes. In searching for techniques, every tutorial or DIY always uses some sort of adhesive, even for sewn patches. For a permie, that begs the question of alternatives for commercial kits, glues, and goops.

If the glue isn't pliable, that's a less desirable option for garments that need flexibility of movement. If the glue is water soluble, it may or may not be useful depending on whether the repair includes sewing.

It is rather flexible. The pic of the unstrung, strung, and drawn bow shows how much range of motion the glue must flex while under tremendous force. The bows were often overlaid with rawhide, leather, rayskin, cherry bark, etc. and the glue held them during the entire range of flexure.

One reason it was used was its better than average water resistance: https://www.newmalaysiankitchen.com/fish-maw/#:~:text=Fish%20maw%20is%20dried%20swim%20bladders%20of%20large,in%20food%20industry%20to%20create%20water-resistant%20glue%20(source). I doubt it would take long term wetness, though (it is collagen and would, if nothing else, eventually rot, but so would leather). One advantage of this glue was that it could be reconstituted with a mix of alcohol and water, and I think even steam to make repairs. Many of these cultures lived in tents, and you can imagine the standard weather patterns to which they would have been exposed. The bows would have been used for hunting and war, neither of which tend to wait for better weather. They were used in rather arid regions, though, but I understand this was more of a result of the humidity's effect on the sinew rather than the glue, as it greatly diminished the efficacy of the bow.

M Broussard wrote:For a waterproof, natural glue with some flexibility, you could try making cheese glue (it sounds weird, but I have used it and it's pretty good!).

Okay, so I've been doing some research on M's suggestion of cheese glue, because a waterproof glue with some flexibility sounds like what I'm looking for.

Cheese glue is also called casein glue (casein being one of the two proteins in milk) and when mixed with an alkali, it makes glue. Here are some links for resources:
  How to Make Casein Glue
  Using lime and cheese glue

In addition I found:
  How to Make Leather Glue (gelatin based)
  "Medieval Glues Up to 1600 CE" - That one is a PDF discussing the various glues made during the middle ages, and how they were used. It mentions cheese glue and hide glue (used for wood and vellum), but also gum ammoniac, which is a resin based glue recommended for leather.
  English translations of a section from Il Libro dell' Arte - Includes directions for making fish glue, goat glue, and cheese glue.

Hide glue will work but to make a patch you would probably want to sew it on.

I've heard of bluebell bulbs (Endymion) being used as a paper glue - just rub a cut surface on the paper. How well this translates to leather I wouldn't know, it'll be carbohydrate based rather than protein.