Anyone autoclave hot hide glue?

[roger wiegand]

The latest batch of glue granules I got seems to grow mold faster and in bigger variety than any I've had before. I can't let it go 48 hours between reheating without getting a carpet of aspergillus and penicillium.

So this got me wondering whether it would cause any bad issues if I were to make up canning jars with reasonable amounts of glue in them to quickly melt and use and then autoclave them in a pressure canner to sterilize the glue and jar.

Will heating the glue to 240-250 F for ~20 minutes degrade it in any significant way? Knowing what I know about collagen I wouldn't think it would be a problem, but does anyone have hands-on experience? I'd worry about making joints that appeared fine initially and then failed down the road. I've tried boiling and that doesn't seem to create any apparent loss of strength, but it's also not fully effective at sterilization.

I'm mostly gluing leather to wood in organ work, not a high strength requiring application.

[russell lusthaus]

I would not heat it very hot - not over 160 or so. That is what I was taught - not sure why - maybe a breakdown of collagen, etc. Keep it in the freezer or fridge in between sessions. I make ice cube trays of glue - and transfer to zip locks - and use as needed.

[Dave Fitzgerald]

No experience doing this with hide glue. But, if I wanted to heat-inactivate it, I would try Pasteutization on a small scale. You don't really need it to be sterile - the objective would be to just knock down the population of bugs in the product. Make up a batch, heat it in a hot water bath until the temp. of the solution reaches 160 F, hold it there for 15-30 seconds, then cool to your regular working temp. and/or store in the refrigerator.

[roger wiegand]

I like the ice cube tray idea, I think. Do you keep them frozen? Have to try the experiment, off hand I don't know whether freeze-thaw or overheating would be more damaging to the protein. Popping in as many cubes as needed for a day sounds efficient. Now I throw away almost as much glue as I use.

l already know that brief boiling is insufficient to do in the mold spores, so I don't think a 160 deg pasteurization will do the trick. Keeping glue in my Hold-Heet pot all day at ~145 degrees doesn't particularly faze the buggies. If I heat it every day it's OK, but if I skip a day I have colonies growing.

I'm sure keeping it in the fridge would help slow down the growth, but might also stress marital relationships. ;-) (For some reason, some folks don't like the smell)

[chris carter]

I make hot hide glue in batches and pour into a 1" silicone ice cube trays. They are flimsy so I let them set up and then move them to the freezer. Once frozen I pop them out and put them in a tupperware container and keep them in the freezer. When I need to glue something up I pull out however many cubes I need and throw them in the pot. My pot is a little glass jar in a baby bottle warmer with a mark on the dial for the proper temp. Works flawlessly. When it comes to leftovers, if I know I will use them within a few weeks I'll just stick the jar in the fridge with a lid. If I added salt, then I put a tiny post-it note on there that says "salt" so I know. If it will be a while, then I just pour the leftovers into the mold and put it in the freezer and then pop it out and back into the container. If I added salt, then I don't refreeze - not because you can't, but because I won't know that cube(s) has salt in it and it will get jumbled up with all the other cubes. I have had cubes made of glue that has been frozen a few times with no issues. I think you can refreeze indefinitely.

Be aware that you loose a little moisture in the freezer. If you have a defrosting freezer you will lose more. If you keep it in a regular chest freezer that's not frost-free, like I do, then you will get some ice crystals that separate from the cubes. It's fine. It just means that I have to add a smidge of water when heating up. I keep a spray bottle of H20 in the shop and it mostly gets used for this purpose as I don't have running water in there.

[Mel Fulks]

I used to do some work for a guy who made and repaired violins, he insisted on buying the stuff that was sold in almost colorless sheets.
Not granules. Might have been rabbit glue.

[Robert Engel]

Hide glue is cheap enough, try to mix only what you need, ideally you're making a new batch each day. If I'm not using it within a few days, I keep it in the fridge. If it looks funky I discard it and mix up a fresh lot.

I think that high a temp will denature the protein, my understanding is never heat beyond 150°

[russell lusthaus]

Just like chris, long term storage in the freezer and shorter term in the fridge. I use the glass jar with marbles in the crock pot method for large batches. I have the very small hide glue pot from Lee Valley for small (2 cubes). Wish it were just a tad bigger.