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Dissolving old glue
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Author:  Conor_Searl [ Wed Dec 12, 2018 10:58 am ]
Post subject:  Dissolving old glue
Is there a way to dissolve old glue that is on wood? As a sub question, is there a way to tell by appearance what kind of glue a person is dealing with? I'm working on cleaning up a failed headstock repair (see earlier post about the '57 Gibson) and there's a lot of glue. If I can avoid hours and hours of scraping the lions share of the glue off the surface of this break that would be awesome!

I did try using a soldering iron and damp towel but it seemed to have no effect, this particular glue almost looks like lacquer, it's clear and has a nice gloss.
Author:  profchris [ Wed Dec 12, 2018 12:13 pm ]
Post subject:  Re: Dissolving old glue
I can't tell from the photos on the other thread, but if it *is* water soluble then it might be hide glue. Steam ought to have made the surface sticky if so, but old hide glue takes quite some time to start to dissolve/liquefy. Your damp cloth might not have produced enough steam, or for long enough, to soften the glue.

Get a cotton wool bud and a cup of hot water, and get a small part of the glue surface wet. Keep wiping with a hot bud (rinse to get it hot again). After a few minutes you might see a change in the surface appearance of the bit you're working on, and the bud starts to feel sticky. If so, you're winning! Basically, keep going until it's all gone. It will take ages, but if it's hide glue and you re-glue using hide, then leaving a very thin film of old glue on the surface is fine because you've partially reactivated it during cleaning, and although it will dry the new hide glue should reactivate it. But you mustn't leave more than a smear!

If this doesn't work then it's not water-soluble. I believe that acetone might be the next thing to try, but wait for words from others who know rather than just believe :)
Author:  Conor_Searl [ Wed Dec 12, 2018 1:45 pm ]
Post subject:  Re: Dissolving old glue
profchris wrote:
but old hide glue takes quite some time to start to dissolve/liquefy.


Just to get some perspective are we talking 5 minutes or a half an hour?
Author:  B. Howard [ Wed Dec 12, 2018 4:29 pm ]
Post subject:  Re: Dissolving old glue
Could be epoxy..... Most unqualified techs prefer it as they think it will work better. Most of the failed repaired head breaks I see were done in epoxy. Stripper with MEC in it (BTW if you haven't heard the stuff with MEC is going bye bye from the stores next year...). will work but it will not be absolutely clean when done and vapors are deadly. Oh and any finish in the general area will be toast too. Epoxy will also release with heat, usually about 300 D F. again toasting the finish and possibly weakening other joints like the FB.
Author:  Wayne Brown [ Wed Dec 12, 2018 8:03 pm ]
Post subject:  Re: Dissolving old glue
It's probably not Titebond but as a matter of information, vinegar will desolve Titebond glue. I had read this somewhere and it worked great on one of my repairs.

Wayne
Author:  profchris [ Thu Dec 13, 2018 10:50 am ]
Post subject:  Re: Dissolving old glue
Conor_Searl wrote:
profchris wrote:
but old hide glue takes quite some time to start to dissolve/liquefy.


Just to get some perspective are we talking 5 minutes or a half an hour?


I'd expect to feel some stickiness in 5 mins or so, even with pretty old glue, and would give up after 10!

Epoxy was my other guess, but I've no experience with that - Brian Howard has explained all, and it sounds just as tricky to remove as I suspected. Fingers crossed for you.
Author:  Conor_Searl [ Thu Dec 13, 2018 12:19 pm ]
Post subject:  Re: Dissolving old glue
B. Howard wrote:
Stripper with MEC in it (BTW if you haven't heard the stuff with MEC is going bye bye from the stores next year...). will work but it will not be absolutely clean when done and vapors are deadly.


MEC? Are you familiar with this brand? There is no list of ingredients on the side...

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Author:  Conor_Searl [ Thu Dec 13, 2018 12:23 pm ]
Post subject:  Re: Dissolving old glue
profchris wrote:
I'd expect to feel some stickiness in 5 mins or so, even with pretty old glue, and would give up after 10!

Epoxy was my other guess, but I've no experience with that - Brian Howard has explained all, and it sounds just as tricky to remove as I suspected. Fingers crossed for you.


Yeah I spent a good 10-15 minutes on a couple small spots with both boiled water and cotton like you suggested, as well as a damp rag and soldering iron. It didn't even get a little tacky. And scraping with a razor just left little white scratches. It's seeming more and more like it might be epoxy. But I'll pick up some acetone and try that as well as the stripper I have at home and see if that gets me any where before resigning myself to scraping it all off.
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