Hide Glue – New Information Found Part 1

I’ve done extensive research and have written several articles on this glue. I thought that’s all the information there is until I met Eugene. He was kind enough to release a 15 page dossier on this glue. He’s been working with and selling hide glue since the 50s and he has summarized and simplified the information of the last 70 years of working knowledge in 15 pages. Make a cuppa, sit back and have a read. I will not post all 15 pages in one post, but will do so in several posts over several days.

BY: EUGENE  B  THORDAHL

“40 Centuries Old And Still Holding”

INTRODUCTION

Nearly 4,000 years ago, the Egyptians were using hide glue for their furniture adhesive.  This is proven by chairs found in Pharaoh’s tombs and by stone carvings depicting the process of gluing different woods.  Hide glue is still in use today for wood gluing and over the years much has been written about the manufacture and use of hide glue for hundreds of other adhesive applications.  With the evolution of synthetic (ready to use) adhesives, hide glue has taken a lesser role in industry but has maintained a major role in repair and restoration of antique furniture, reproduction of period furniture, restoration, production and repair of musical instruments as well as numerous other applications.

HIDE GLUE PRODUCTION – FROM HIDES?

Yes, from animal hides, almost any animal but primarily from cattle hides.  This is simply because of the abundance of cattle hides due to the enormous world wide consumption of beef and subsequent tanning of hides for leather.  The trimmed hide pieces (too small or irregular shapes to provide useable leather) are shipped to the hide glue plant.  The glue manufacturing process is basically the following:

  • wash to remove dirt
  • soak in lime water for 60-90 days
  • wash to remove hair and lime
  • neutralize with acid, drain, wash & drain
  • add water, heat to 110-120o F for 2-4 hours (called an extraction)
  • drain off the dilute glue solution, evaporate, chill, dry, grind
  • repeat last 2 steps 3-4 times to extract all of the glue with the temperature being increased 20-25o F each time.

The process can lend itself to “home brewing” but it is messy and the aroma is found by some to be less than exciting!  Your best bet is to buy the finished product from a reliable supplier.

CHEMICAL COMPOSITION

Hide glue is a protein derived from the simple hydrolysis of collagen which is a principal protein constituent of animal hides.  Collagen, hide glue and gelatin are very closely related as to protein and chemical composition.  An approximate chemical composition for glue is:

                        Carbon                                   51-52%

                        Hydrogen                              6-7%

                         Oxygen                                  24-25%

                        Nitrogen                                 18-19%

                                                                         100 %

The molecular weight of hide glue has a wide range from 20,000 – 250,000.  The higher the gel strength, the higher the molecular weight.

TESTING HIDE GLUE AND STANDARD GRADES

Peter Cooper, founder of the domestic glue industry in the early 1800’s, is generally credited with developing the standard methods of testing and grading glue.  The standard is recognized worldwide.  The main components are viscosity and gel strength (or jelly strength which is measured in grams).

The viscosity and jelly determinations are made on a 12.5 percent solution of hide glue, employing 15 +/- 0.01 g of commercially dry glue with 105 +/- 0.2 g of distilled water at 25o +/- 2o C using a standard 150 ml test bottle.  The viscosity is determined by timing the outflow of 100 ml of the glue solution at 60.0o C from a calibrated glass pipette under closely controlled conditions.  The millipoise value is determined by proper reference to the time of outflow in seconds and the constants of the specially calibrated pipette.  The jelly value in Bloom grams is obtained by subjecting the viscosity sample to rigidly controlled gelation in a water bath maintained at 10o +/- 0.1o C for 17 hours, followed by measurement of the force in grams required to depress the surface of the glue jelly 4.0 mm by a mechanically loaded plunger approximately 0.5000 inches in diameter, using the Bloom gelometer.

A chart of Standard Grades follows.  Note the glue grade designation is the “Standard Mid-Point Grams”.

Standard Hide Glue Grades

Standard Mid-Point Grams  Range GramsStandard Millipoise ValueRange Millipoise ValuePeter Cooper Grade Designation
512496-529191183-1995A Extra
477461-494175167-1824A Extra
444428-460157152-1663A Extra
411395-427145138-1512A Extra
379363-394131125-137A Extra
347331-362121113-1241 Extra
315299-330111102-1121 Extra Special
283267-29810192-101No. 1
251237-2669283-911XM
222207-2368275-821X
192178-2067267-741-1/4
164150-1776360-661-3/8
135122-1495853-591-1/2
10895-1215347-521-5/8
8570-944437-461-3/4
5847-693428-361-7/8
3210-463020-27No. 2

GENERAL PROPERTIES:

            Moisture:                    10 – 15%

            pH                               6.0 – 7.5

            Form                           Dry Granular 8 – 10 Mesh

            Color                          Yellow/Amber to Brown

            Specific Gravity        1.27

A later discussion will present the value and reasons for using different grades.  Generally, the higher the gel strength (in grams):

  • the higher the molecular weight
  • the higher the viscosity
  • the faster the tack and set

the shorter time you have to complete a lamination

6 thoughts on “Hide Glue – New Information Found Part 1

  1. Thanks for the information. Looking forward to the information. You might find this amusing. I work in the biotech industry on the chemistry/manufacturing side of things. While working at a large biotech company, I took a tour of their big manufacturing facility. When growing up cells to make your biological product, you put them in a broth that nutrient rich so that they can grow easily. The challenge is that you don’t want other things growing. As such, there is one step used called HTST (high temp, short time – it’s really like flash pasteurization). All of the media goes through this to kill anything else so that when you add the cells you care about, they are the only thing that can grow. Even though this step is contained, it stinks to high Heaven and makes me want to gag. The folks who run it smiled and said, “it smells like money.” I don’t know what hide glue extraction smells like, but I can guess.

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  2. The Brooklyn Museum has X-rays of the joinery in the slatted seats of Egyptian chairs showing that the mortises are surprisingly loose fitting and that the glue has been mixed with some kind of calcium powder to fill the gaps. I asked about it but they couldn’t say for sure if it was something like alabaster dust or maybe a gypsum (plaster of Paris) mixture .

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  3. This page shows examples. https://www.brooklynmuseum.org/opencollection/objects/3948 Most of the joints seem to contain (to some degree) a glue/powder mixture. I experimented with some chalk and hide glue when I was making an Egyptian style cabinet on stand recently but it didn’t seem as strong as straight glue in my test pieces, so I didn’t use it on the final. I’m going to make a slatted/scooped seat stool next and will try it out on the tenon slats.

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    1. It just goes to show what it means having a workbench and securing your stuff to it. How in the world were they able to cut accurate shoulder securing the work with their feet. I haven’t seen any workbenches or vices in any paintings. That’s my only explanation as to why there are gaps

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