(03-21-2017, 02:16 PM)sussertown Wrote: I just read a very interesting article on Hide Glue and making your own in a wood magazine. Maybe newsletter. So, I sent a letter to the writer to simply mention that the statement about breaking wood when trying to dislodge hide glue was confusing as violinists and luthiers remove parts of glued instruments with a tap of a mallet and no damage.
The other thing I wrote was that I followed his explicit instructions. add salt, heat for two hours, refrigerate, heat for two hours more. The glue was liquid, for a while. Now it's more like honey. Anyone know what I did wrong? Altitude?
I believe you are referring to the formula given by Don Williams for making a "liquid hide glue".
Yes, it does gel down to a honey like consistency in the bottle. But it will eventually harden when exposed to air so that the water can evaporate.
Personally, I think it is a bit TOO slow and I cut the salt in half if I'm making his recipe.
For 192 gram strength stuff in the glue pot (120F to 140F) I add about 1/2tsp of salt per 1/3cup of glue granules. Seems to slow things enough for me. This is also less than the formula given by Joshua by about 1/4 the qty of salt per glue granules. I mix smaller batches as 2/3cup of liquid glue lasts me a while.
I also add a few drops of household bleach per batch cup of liquefied glue so that it doesn't mold as quickly. I don't use it every day so into the fridge it goes. But with the fridge, salt and touch of bleach, it stays good for me on the order of months. Oh, and using a condiment bottle to mix and store the glue works great! I just pop it into the glue pot to warm up and then can squeeze out what I need.
I don't build musical instruments, but I do use the hide glue for furniture type joints. And I don't spare the glue when working with it. I'd assume joining the top to the sides of a violin, one isn't going crazy with slopping on glue. I believe there is some relationship between density of wood, volume of glue, dilution (runny vs. thick) of glue and final shear strength of joint given the way hide glue bonds as opposed to "modern" plastic glues.
Out of curiosity, when you are disassembling instruments, are you applying any heat or moisture first? And also what gram strengths are used in luthery? I'm using mostly 192 (slower set) and 135 (rapid set) for joinery work.
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