When I proposed the 100 mile ART project I was all too aware that my experience in using entirely locally collected materials had a few holes in it; glue making is one of them. Glue shows up in many areas of painting an icon: The woodworking, gilding and gesso work all rely on a good glue, and hide-glue can be used in all these applications. As you can guess from the name, hide-glue is made from an animal’s skin. While any animal hide will make some glue, different types will produce stronger and weaker glues. A favourite type of hide glue among iconographers is that made from rabbits because of it’s high strength. By boiling the hide the collagen is released and this can then be used as an adhesive – at least that is the theory …
So, my first task was to find some rabbit pelts. A Mennonite friend of mine has his daughter raising rabbits as a small side business for her. He gave me the contact information for Abate Rabbit Packers in Arthur, Ontario where his rabbits go to be slaughtered. The owner, Joe Abate, was happy to sell me a few hides and so I headed up to Arthur to collect the pelts. In conversation, Joe (who is the third generation involved in rabbits) was interested in what I was doing and even gave me a few older rabbit skins just in case that would make a difference to the process. With the box in my trunk, I headed home.
Unlike most people who deal with pelts, my first job was to get off the hair and the method I decided to try was to submerse the hides in limewater. I knew from some different sources that this should remove the hair, but it also had the benefit of being something that the glue industry does to soften the hides before extracting the glue. So, I made up a bucket of limewater and put the hides into it.
As the week went on, I checked on the rabbit pelts a couple of times to see if the fur was loose enough to remove. After a few days, I could begin my glue making attempt!
By this time, the hair came off very easily and there wasn’t much work in it. Scraping the underside still needed to be done and this took a little longer, but in the end I finished that without too much trouble. I used an old hacksaw blade to do the scraping. For the first pelt I tried just holding the blade with my hands, but I tired quickly. So I took the time to make a little handle for the blade (you can see it in the top photograph) and it worked much better for me.
Once I had this finished it was time to boil it. Actually, boiling is a bit of an exaggeration; I kept the water at around 75C. This is because, with any type of hide glue, the higher the temperature the weaker the glue. While it was steeping, I kept revisiting the pot and putting a finger into the liquid. It took about four hours for the water to become sticky, but it finally did! I then poured off the liquid and refilled it with clean water. I allowed this to sit to extract more glue. Each subsequent soaking took only about two hours. I was able to repeat the process three times in total and each time I ended up with the same sticky water. In the end I filled up a big pot of “glue liquor”.
This glue liquor now needed to be reduced so that the glue can be allowed to set and then dried out for later use. So far, the liquid looked a lot like the hide glue I’ve used in the past.
In the background throughout the next busy day, I kept one eye on my pot of glue liquor. I kept it at roughly the same temperature as when I was steeping the pelts and little by little the water went down. I was surprised at how much of the liquor is actually water!
When the day was done, I thought it was reduced enough (the glue had started to stick to the bottom of the pot unless I stirred constantly). I poured it into two cookie sheets to set to see what we would have in the morning …
The morning after I set out my reduced glue liquor I found that it had set, but not to the firm state that I had hoped. If I was to use jello as an example, I found that my glue had set to regular jello rather than the “jiggler” consistency I had hoped for. This is a very appropriate analogy to make because the jello we know and love has it’s roots in this same materials and process that I have been exploring here, and to this date the difference between what is dubbed as ‘glue’ or ‘gelatin’ simply denotes whether the substance is food grade or not!
So I decided to heat it up again and remove more water if possible. What I found was that I needed to reduce the temperature to about 50C in order to not have a glue sediment form in the bottom of the pan. This done, the mixture seemed to continue to reduce well until I had only enough for a single pan full.
After letting this batch sit for the afternoon I had achieved my “jello jiggler” and I then began to doubt whether that was thick enough. Once a hide glue is dried, it lasts almost indefinitely but if it is wet it will go moldy in about a week. I really didn’t want my hard won glue to develop mold …
That’s when inspiration whispered in my ear: Warming Oven. Our old Moffat stove is from the 1950’s before microwaves were around to reheat dinners, so it has two ovens beneath the elements, one for baking and one for keeping dinner warm until the missing family member came home. There is no thermostat on the reheating oven, it just gets warm, so I flicked on the switch and put my single pan-load of hide glue in.
It seemed to be working perfectly, and after another couple of hours in the warming oven my glue came to form a nice, thin layer in the pan. So I peeled it out of the pan and put it on paper to dry-out.
Unfortunately I couldn’t peel it out in one big piece (it would have made a great photograph!) but I did get all the hand-sized pieces to release in the end.
By the evening, these pieces were getting quite hard and I expect I’ll be putting them into a jar for later use. In the end I’m quite surprised that three pelts produced only a thin, pan-filled amount of glue and I suspect that I could do better if I were to pay more careful attention to the temperatures at which I steep the hides.
What I have from this batch will be great to experiment with when it comes time to create my first batches of gesso but I think I’ll need to try and repeat the process before I’m finished with this project!