Hide Glue Test

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.

Step 1:

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.

Step 2:

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.