Has anyone ever tried to thin epoxy with MEK, I know that the directions on MEK mentions one of its uses as thinning epoxy. I just wonder if this would weaken the epoxy more or less than denatured Alcohol? Thanks for any comments or suggestions.

Never tried MEK... that stuff is nasty. I have some around for reducing auto, er I mean airplane paints.

In general, anything liquid added to expoy will weaken it. MEK will evaporate really fast, but I guarantee some will still get trapped in the epoxy, which will weaken it.

The best way I have found to thin is with heat. Warm up the bottles before you mix in a water bath. You can also warm the epoxy after it is applied with a heat gun. The heat will make the expoy set quicker. I've heard that added heat can also weaken the cure, but as long as you keep the temp reasonable, say 120F or under I think you'll be fine.

If you are trying to fuel proof, you can also use heat, but since strength isn't as important, you can get a bit hotter. I'll pour, slather, brush in, etc the epoxy. Hit it with the heat gun, then use a playing card to scrape off the excess. Makes for a pretty thing and light weight fuel proofing. Only way I know of to get thinner/lighter is to use dopes. I don't like the dopes because they never really cure and remain tacky for a long time.

I have used it, it works pretty well, but heat works well too. Depends on how thin you want it.

MEK (methyl ethyl ketone) is just another organic solvent. There's no advantage to using it to thin epoxy over another chemical such as alcohol. MEK vapors cause liver damage but require long term exposure to do that. One of your previous replies makes sense. Depends if you want to thin the epoxy just to use as a fuel proof sealer. In that case alcohol will work just fine. If you want to thin to fill a gap, check the LHS for another alternative. If the epoxy is to be used for structural strength of a joint, stay away from adding a 3rd. component to the 2 part mix.

I've used denatured alcohol with good results.

Acetone works too, but that is not a healthy solvent to use like MEK.

Don't use rubbing alcohol. That has too much water in it.

I prever denatured alcohol as it is not so caustic.

Check out: http://www.westsystem.com/webpages/e...ningEpoxy.html

I have always used the basic Isopropyl alchohol, ie rubbing alchohol.

I have never encountered a strength problem.

If the rubbing alcohol has too much water, the epoxy will not cure. I have seen people who have used it and the epoxy never cured, always stayed sticky and was not fuel proof.

There are different grades of rubbing alcohol. Read the labels; some are better than 90% pure. The really cheap stuff has a lot of water in it.

I agree with monkeyboy, don't thin it if you can do it another way. I've seen to many people try thinners then complain about slow cure, no cure or sticky results. If you must use alchohol, don't use rubbing alchohol (all rubbing alchohol has a large water content), use denatured alchohol available in the paint section of most hardware or paint stores. Mild heat (less than 200 degrees) does not weaken it and certainly makes it very flowable and does decrease cure time. If you have a choice, use heat.

the only reason i thin epoxy is when fuel proofing the fuel tank area, firewall exposed wood on the outside etc. rubbing alchohol, just never use somthing called IV prep( if your a diabetic with an insulin pump you know what that is) IV prep will ruin the epoxy, it too watery

Thanks for the info, my primary purpose for thinning was fuel proofing. everybody has really given me more options to choose from...

My LHS stocks some stuff from BSI (Bob Smith Ind. I thnk?) that is called 20min "finish cure" epoxy. it's pre-thinned, almost watery. Really easy to work with for fuel proofing fiberglass work. Sure, it might be cheaper to thin it myself, but I like the no-thought-needed aspect.

Use an epoxy specifically designed to be spread thin, like Z-Poxy finishing epoxy.

Hi ya'll,
We all should know there is an almost universal thinner that
works fine with just about anything modelers might use.
Plain old Acetone which evaporates so easily and quickly it
should not change tha character of anything, OK?
Good luck!

Hal deBolt

Hal,
Great to see you here! Didn't realize that you spend time in RCU.
Dennis-

Just don't use Acetone to thin expoxy for use over foam or your airplane will get to play "wicked witch" . I do a fair amount of fiberglass right over foam.

Hi DB,
Yes I spend time with RCU, find it interesting.
Now have made a bunch of posts, mostly in Aerodynamics and Autogyros which are my current passion.
You are in Ma.?
By any chance familiar with my fine friend Harvey Thomasian?
If so, what is the latest with him?
SUL and good luck!

Hal [email protected]

P.S.> Kirk is so right, don't get Acetone anywhere near foam!!