Full Chisel Blog

February 6, 2012

‘What the hell is 192 grams Bloom?’

Filed under: Alchemy,Hide Glue,Historical Material,Of Interest,Publications,Uncategorized — Stephen Shepherd @ 10:22 am

That was a question asked me by a friend that is starting down the short sticky slope of hot hide glue.  He had asked what to order and I told him ‘192 grams Bloom’, to which he gave the above response.

I then explained to him about how the strength of hide glue was determined using a [Oscar] Bloom Gelometer to establish the strength [molecular weight] of a sample of hide glue.  A mixture of 12-½ wt. % protein solution (known as standard concentration) of hide glue is prepared by heating the hide glue and water for 18 hours at 50° Fahrenheit and tested in the following manner.  A plunger ½” in diameter, with a flat bottom (1/32″radius on the lower edge) is pressed about 3/16” (4 mm) into the solution.  The English/European system differs slightly.

Glue comes in strengths from 12 to 529 double Bloom grams, the highest coming from the first extraction of hide glue during the manufacturing process and divided into several grades.  The numbers given like 192 is the midrange; between 178-206 considered the best for general woodworking.

I then told him to read all about it in Hide Glue – Historical & Practical Applications and to order some 192 from Joel at Tools for Working Wood.  He sent in the order for 5 pounds and gave me a pound, good thing as I am down to my last half pound.

Stephen

3 Comments »

  1. I recently disassembled and rebuilt a table that had been in the barn of our new-to-us house for donkeys years. I had to separate the skirt from the legs to repair some worm damage, and the pegs popped out easily of the mortice and tenon joints easily and the parts separated no problems. The weird thing was the joints weren’t draw-bored, and there was no trace of glue in the joints. I have read, but don’t know where, that one thing with hide glue is that if the humidity gets up, bacteria can literally eat the glue out of the joint, and this seems to have been the case here. Seems like the joints must have been glued originally. Is this true of hide glue?

    Comment by Brian Anderson — February 8, 2012 @ 3:02 am

  2. Brian,
    A lot can happen to hide glue over time, it can completely dessicate, turn to powder and fall out. Bugs love hide glue and can literally eat the glue away. Bacteria could also attact hide glue.
    Stephen

    Comment by Stephen Shepherd — February 8, 2012 @ 10:48 am

  3. Thanks Stephen, obviously all bets are off if you leave a table out in a barn for decades. But I couldn’t find anything on the subject, and didn’t understand what had been going on with the table, and a couple of other pieces of furniture worth repairing, but in bad shape.

    Cheers, Brian

    Comment by Brian Anderson — February 8, 2012 @ 11:27 am

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