I feel like I’ve only just scratched the surface on this topic which prompted me to add further notes, however I am aware that most people would rather view than read but unfortunately I do not have a professional studio setup with cameramen to aid me so we’ll just have to do it the old fashioned way and read.
Protein glues are made by cooking protein for lengthy time, you could put a soup bone in your soup and cook it for too long and your soup will turn into glue. You have fish glue, rabbit skin glue, bone and hide glue. Fish glue is the only one that is liquid in room temperature but is not as strong as a mixture of bone and hide glue but OBG is not made out of fish glue. Rabbit skin glue is used by guilders to apply gold leaf to their furniture, this type of glue must be diluted quite a bit. Bone and hide is mixed 2/3 to 1/3 to make good furniture glue and are measured in gram strength, this measurement is taken by pushing a tool into the dried glue. The gram’s strength varies from 100 – 500, 135 gram strength is used to make chip glass, 192 is a good compromise and most commonly used for furniture in terms of medium setting. The higher the strength the faster it sets and the more brittle it is.
The beauty of animal protein glue is that it can be used over and over again, be it 1000 or 5000 years old you just reheat it and use it again, I don’t know of any modern day product that can be used multiple times and in a single year let alone 1000 years from now.
In the old days they sold the glue in cakes and would also have the makers stamp on it, to cure it they would put it on a wire mesh so as not to let it get mouldy so they would let it dry hard on a screen so they could later sell it.
Marquetry and veneering cannot be performed with modern day glues, yes they can be glued with modern day glues but they rarely last for very long and so hide glue is the only glue that is used in veneering and marquetry.
I have only ever used liquid hide OBG and Titebond after experiencing the two my preference goes to OBG, on the other hand I have never cooked my own glue. This is an area I would love to explore as OBG is getting far too expensive living so far away from the source. I offered to you a recipe from Don Williams on making your own liquid hide glue with no spoil date. I have written to Patrick Edwards about this but he hasn’t responded.
It may seem medieval to some to resort to what may seem like primitive methods of gluing two sticks together and even some what cumbersome to make when readily available modern day glue off the shelf works perfectly fine. All be it I believe it is the perfect choice for gluing timber and without repeating all the benefits of using animal protein glue please refer to the first article but in terms of cumbersome or time consummation of making the glue I believe the time difference between making it or using PVA or yellow glue actually consumes the same amount of time. HA???? How you may wonder. To clean up modern day glue properly takes more time than it does to make Hide glue. I did say they are on par here but after thinking about it I figured it actually takes longer to clean up the mess. With hide glue you can wash it off which only takes minutes but with PVA or yellow glue washing it off after it has dried is not possible and you can’t get a chisel in those tight spaces without risking digging into your furniture piece. So in hind sight it makes perfectly good sense to incorporate hide glue in your everyday woodworking.
I believe this now concludes what I know about animal protein glues, I’m sure there is more information out there on the net if your still eager to know more about it. All I need to do now is figure out where I can purchase 25kg bags of the stuff.