I just want to start this post by saying, “I love to use hide glue.” Hide glue was an interesting part of furniture repair when I began my apprenticeship. It was a smelly new tool that the shop dog loved to eat off the floor whenever I scraped the excess from a repair. I learned over the years that hide glue has been around for a very long time and still has it’s place in the wood shops of today. It may not smell the best, but you can get used to it.
I recently made a new batch of hot hide glue and noticed that the glue never gelled back to a solid mass after the glue pot was unplugged. That was odd. So to be safe, I used my Ol’ Brown Glue (a hide glue product that does not require heat to use). I was baffled by the glue batch that would not harden without heat. I do remember pouring the granulated glue into the pot at the end of the day, and figured maybe the pot was still warm and it affected the new batch. So, I poured that out in a hole by the pear tree for fertilizer and made a new batch. This This second batch had the same result! I immediately went to the authority on hide glue on my bookshelf. A book by Stephen A. Shepherd, Hide Glue: Historical & Practical Applications. (I highly recommend the book!) He talked about a way to test your glue. So, I did it and I want to show you how I did it.
I measured .5 oz of granulated hide glue from my bag of 192 gram strength and 251 gram strength (the 251 g was a newer bag of glue) and mixed them with 2.5 oz of distilled water.
I waited about 3 hours and looked at my results.
The 192 g was very watery still and not seeming to absorb like the 251 g.
Now this batch was much more like jelly and even the watery liquid was thick.
So, I decided to check the instructions to see how long I needed to wait to get my results. Shepherd says [paraphrased] that hide glue will absorb 5 times it’s weight in water and the test should be performed overnight. The next day all the water should be absorbed and a stiff jelly substance will mean you have a good batch of glue.
So, I waited overnight. The 251 g glue passed the test and the 192 g did not.
Not only was there water not absorbed, the glue smelled rotten too. So, I will have to see about a better way to store my glue than in the zip lock style bag it comes in, even if it does come with a silica absorber. It was only 1 1/2 years old just for the record. So, if you are unsure about your granulated hide glue, this is an easy test you too can perform. I weighed my glue and water with a digital postal scale. Thank you Mr. Shepherd for your hard work on researching and sharing that information in the form of your book. I hope this post helps demystify the scary aspects of hide glue.