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Temperature sensitive epoxy problem

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Forum topic by Azalin posted 01-07-2021 01:17 PM 498 views 0 times favorited 7 replies Add to Favorites Watch
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Azalin

2 posts in 94 days


01-07-2021 01:17 PM

Topic tags/keywords: epoxy guitar finish

Hello,

I’m new to the forum. I’m a hobbyist and am building guitar for myself to meet my taste.

I tried something new and made a jigsaw puzzle electric guitar body. Routed all the pieces individually, and used epoxy to glue them together.

The epoxy cured in room temperature (like 20C). Now it is fully cured. I also took a sample from the same mix to examine how hard it gets. It is very hard actually. I like it. The problem is when I slightly heat the sample epoxy, like just above body temperature it gets soft. So the same will happen to the guitar body too at warm summer days. The stress of the strings will pull the body bend and because the epoxy is softened it will tend to bend.

Is there anything I can do to prevent the cured epoxy getting soft, more temp resistant? Or do you think the work is a total failure?

Edit: Forgot to mention, thickness of the epoxy between pieces is about 2mm.

Thanks,
Suat


7 replies so far

View mitch_56's profile

mitch_56

58 posts in 1524 days


#1 posted 01-07-2021 02:20 PM

You either used the wrong kind of epoxy (e.g., you used a casting resin instead of a laminating resin), improperly mixed it, you got contaminants in your mix (maybe you mixed in dirty containers, or some solvent or oil got into in to the mix), or you got a bad batch.

Something to test: take your sample, and post-cure it according to the manufacturers directions. Then try to get it to warm it and see if it gets soft again. Probably won’t help, but there is a tiny chance it will help enough so that you don’t have to scrap the guitar and start over, and a tiny chance is better than no chance.

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SMP

3772 posts in 956 days


#2 posted 01-07-2021 02:39 PM

What kind of epoxy? I had similar problem with Gorilla epoxy recently so am never buying that brand again.

View HokieKen's profile (online now)

HokieKen

17233 posts in 2189 days


#3 posted 01-07-2021 03:00 PM

Yes, what kind of epoxy? I have to agree with Mitch, this isn’t normal behavior for most epoxies. Even casting resin shouldn’t soften noticeably at temperatures that low.

Did you mix anything into the epoxy like dye or pigment? Maybe it wasn’t compatible?

I would contact the epoxy manufacturer and see if they have any suggestions. Unfortunately, I don’t see much hope of salvaging what you’ve already done unless the manufacturer can suggest a way to resolve the issue.

-- I collect hobbies. There is no sense in limiting yourself (Don W) - - - - - - - - Kenny in SW VA

View bilyo's profile

bilyo

1345 posts in 2153 days


#4 posted 01-09-2021 12:06 AM

You say the the glue line is about 2mm thick. So, the epoxy was used as a filler as well as a glue. I don’t understand the chemistry involved, but I found out the hard way (similar to you) that it doesn’t work. I tried to repair a chair with very loose joints. The gap around the rungs was also about 2mm. After the epoxy cured, it also failed under stress. I contacted the manufacturer and they informed me that ordinary epoxy glue is just that, glue. It is not formulated to be a filler. There are also formulations made for that purpose. You can also buy fillers to add to the glue formulation that will give it better strength in that use. In my chair repair, I ended up re-doing it and added sanding dust to the epoxy glue until the consistency was like peanut butter. Once the epoxy was cured, it was very strong and rigid and has held up well since.

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Foghorn

1143 posts in 437 days


#5 posted 01-09-2021 01:27 AM

If you’re still here Azalin, that’s a really cool guitar and design. It would be a shame if you had to scrap it for epoxy fail. I don’t know what you used and others have asked above, but tried and true epoxies like West Systems, G2 and System 3 are reliable. Having said that, a good PVA wood glue likely would have worked fine. Good luck.

-- Darrel

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Azalin

2 posts in 94 days


#6 posted 02-24-2021 08:29 PM

Hello,

Yes, I’m still here and I owe you an apology for not replying.

I wanted to post the end of the story. I decided to finish this project, and taking the risk but so far so good. No cracks or bending yet but I think I need for the summer time to see how the epoxy reacts in higher temps.

Thank you for your help people.

Here are some pics:

View Madmark2's profile

Madmark2

2487 posts in 1639 days


#7 posted 02-24-2021 08:39 PM

Nice axe!

-- The hump with the stump and the pump!

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