Epoxy Mixture

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Forum topic by hiswillus posted 07-31-2013 09:42 AM 1250 views 0 times favorited 7 replies Add to Favorites Watch
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70 posts in 2215 days

07-31-2013 09:42 AM

Gluing up a couple pieces of olive wood with a hacsaw blade inbetween to make me up a marking knife. Not sure if I did a bad joint or the wood moved but when I was done there was a gap on one side. Gave it a slight pry thinking there was no way it would just nicely split, but it did! Somethings seems to not be right as the epoxy is just peeling off the wood. I’m pretty sure it’s supposed to bond to it. Any way I’m looking for possible reasons. Either there isn’t enough hardener or maybe the wood is to oily. Any info would be greatly appreciated. ;)



7 replies so far

View Gary's profile


9393 posts in 3700 days

#1 posted 07-31-2013 01:12 PM

I don’t know, Jeff. But I’m going to bump it back up so perhaps one of the smart jocks will see it and give you an answer. I’d like to see what they say

-- Gary, DeKalb Texas only 4 miles from the mill

View Tennessee's profile


2895 posts in 2781 days

#2 posted 07-31-2013 01:24 PM

Olive wood is oily and from your picture it looks like the epoxy has cured, but did not bond to the wood. You sometimes can get this from more than just wood oil. If the epoxy was old, or cured too fast, it can harden before it has time to bond. Also, you do need some pressure to push the epoxy molecules into any pores of the wood available. Did you clamp it?
Just a few ideas…

-- Tsunami Guitars and Custom Woodworking, Cleveland, TN

View hiswillus's profile


70 posts in 2215 days

#3 posted 07-31-2013 01:44 PM

Thanks for the input Paul. yea I had it in a vice along with 4 other clamps. By the way it is West System epoxy so it’s one of the best. It’s possible that I used to much hardener. I surly remember the instructions saying varying the 1/5 mixture could allow the epoxy to dry faster or slower. Going to have to take another look at them. From what you said I’m thinking slower would be better. I’m wondering if I should just use wood glue instead. The teeth in the old hacksaw blade should give me enough texture to keep it from slipping. I’m only using epoxy as that’s what David Fink recommends.

View Tennessee's profile


2895 posts in 2781 days

#4 posted 07-31-2013 02:02 PM

This seems like a good place for Gorilla Glue.

-- Tsunami Guitars and Custom Woodworking, Cleveland, TN

View shipwright's profile


8218 posts in 3065 days

#5 posted 07-31-2013 02:50 PM

You can’t mess with resin / hardener ratios. If it says 5:1,you have to mix 5:1, no exceptions.
The polymer molecules are composed of reagent molecules in a specific ratio.
If you add more of one there will be free molecules of it left throughout the cured mix and they will adversely affect the physical properties of the glue.
Read this blog for a fuller explanation.

-- Paul M ..............the early bird may get the worm but it’s the second mouse that gets the cheese!

View planeBill's profile


506 posts in 2676 days

#6 posted 07-31-2013 02:57 PM

what brand of epoxy says anything about varying the mix ratio? It sounds to me that that and having the piece in a vise and four additional clamps was the problem. I don’t know anything about olive wood. Is it particularly dense? Is it really oily? If yes to either or both of those questions coupled with not mixing the ration correctly and having too much pressure, I would think you had a glue joint starved of adhesive.
Was it West system?
Shipwright must have been typing as I was. He hit it spot on, you can not mess with epoxy mix ratios, period. At least not any of the ones I am familiar with.
Did you prime both or either surfaces first and then add a second coat of epoxy? On more porous woods(if olive wood is porous) one will often need to prime more than once. Usually though it is a good idea to prime the surfaces to be joined with a coat of neat epoxy and then if you are going to use any thickener, apply that before clamp up.

-- I was born at a very young age, as I grew up, I got older.

View Mark Shymanski's profile

Mark Shymanski

5623 posts in 3979 days

#7 posted 08-17-2013 05:54 AM

+1 to what both Paul and planeBill said about ratios!

West has different hardeners for different working times. If you want to slow or speed up the process you need to use the appropriate hardener. West has a pretty good web page which explains a lot of how to use epoxy successfully.

-- "Checking for square? What madness is this! The cabinet is square because I will it to be so!" Jeremy Greiner LJ Topic#20953 2011 Feb 2

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