Official Luthiers Forum!

Does anyone know what the difference is between rapid and extended drying epoxies (other than the obvious)? I was under the impression that the longer the drying time, the stronger the bond, but someone recently told me they weren't sure that this was the case. Thanks in advance.

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It's not the miles ahead, it's the stone in your shoe


In Markham,Virginia

Beyond the obvious observation that cheap hardware store 5 min epoxy sucks, there is no real relationship between cure time and strength. (most 30 min hardware store epoxies suck, too)

As an example, west systems 105 laminating resin will give equivalent results when working with any of the hardeners (205, 206, 209). This is also true with most structural epoxies used in industrial applications

The real reason for different cure times is because it impacts your ability to achieve the correct bond conditions. i.e using longer cure helps when vacuum bagging because it allows more time to get everything situated before it gels. Alternatively, when using heavily filled mixed to achieve gap filling, shorter cure can work better because it will gel before the epoxy runs out of the gap and the filler will not separate before curing.

hope this helps,
-jd

The 5 min stuff I got from Lowes dries literally rock hard within 2 hours and gives me a joint stronger than the wood. When you say you are not happy with the cheap stuff what kind of problems did you have?

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It's not the miles ahead, it's the stone in your shoe


In Markham,Virginia

A lot of hardware store epoxies are crap, but it's hard to tell which ones unless you've tested them yourself. I've had 5-min that went rock hard, and some that never fully hardened even after days.

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services