I've seen 1 other tutorial about making this glue but from dog chews.I used beef & deer rawhide scraps and sinew scraps.I save them all from accoutrament projects and sinewing bows.They accumulate faster the more projects I do.
This time I started with a container holding around 4 pounds of scraps.I was going to use large stainless steel pot on right but used a regular 1 gallon steel can instead.
This container fills a steel gallon can 2 times 3/4er's full and makes 1 first pouring of glue from each one.First pourings makes your strongest glue.I top the can off with water.Turn stove on low and bring temperature up to around 160 F.Not over 180 F.Too hot can weaken the glue.Once up to temp I cover it to prevent a skin from forming on top.
I simmer it around 6 hours each at that temperature to get 1 first pouring each.Any impurities will float to the top and can be skimmed off with a spoon.
I have a miracle whip jar that I cut the center out of but left the threads on the lid with cheese cloth to strain the glue through while pouring.Cotton T- shirt fabric can work too.The amount of water in steel can fills this jar just right.Around 48 fl. ounces and it fills a normal cookie sheet lined with a plastic garbage bag just right then too each time at 1/2" thick glue.
I set cookie sheet out in 45 F. to gell,or putting it into refrigerator can hurry it up too.Nice light blonde colored glue.If your glue is dark you cooked it at too high a temperature.It does'nt totally mean the darker glue is worthless or anything.Still plenty strong enough to do simple composite bows.The lighter colored glue though will be your strongest type glue.I use it on more extremely reflexed bows with good consistent success.
Then after it gells cut it up into 1/2" squares with pocket knife.It'll be like jello if you've ever had that.
I then spread them out on a garbage bag to dry.I put a fan on them.It'll take a full day or two to harden and dry.It can be reconstituted any time for use after that with water.
From the two pourings I got 9.5 ounces.Enough to do 4 to 5 bows.I guess my average would be for every pound of rawhide 2.5 ounces of hide glue is made.
Grinding up the hide scraps to very smaller or pulverized pieces before heating them up can get you more glue too.