Thinning epoxy with denatured alcohol - strength consequences?

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Jan 7, 2013
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Denver, CO
Does thinning epoxy with denatured alcohol decrease the strength of the bond, or permanently change the properties of the cured epoxy in any way? Wondering if the alcohol ends up evaporating from the mix as it cures leaving you essentially the same end result as if it wasn't thinned. Considering a build were I might try injecting internal filets, but the Aeropoxy ES 6209 I have seems like it would be a little thick for that application. As you can tell by this question, I have never injected internals, or thinned epoxy before.
Oh, shoot. I forgot to mention that I already searched the PTM&W website (makers of Aeropoxy products) and found that same FAQ document. Steve, my apologies for taking your time on that.
OK. So, I figured I would go back to the PTM&W website and see about contacting them with this question. Expected to find an email to send in the question, but couldn't find one specific to technical support. So, I called their phone number and within 10 seconds was talking with their technical services manager. Super nice guy. He didn't have any hard data to share with me, but was fairly confident that the denatured alcohol would indeed evaporate leaving a structurally similar result, but did think it would increase cure time. He did ask what I was using the ES 6209 for. When I shared with him that I was using it as a structural adhesive for high powered rockets, he was excited to tell me about a new product, ES 6247. He called it 'toughened', said it was a little thinner, and had higher bond strength in their tests. It's not on their website yet, and he wasn't sure when it would be. He did note that it would cost more (didn't give $ specifically, and I didn't ask).
There's really no strength issues here as it's a widely used formula for glassing RC models. I've done a fully sheeted 1/9th scale B-17 with glass cloth and thinned laminating epoxy. Dries as hard as a rock.
My father, a retired polymer physicist gave me (a biology type) a crash course in basic epoxy chemistry, and while I wont be able to recreate that education here, I can guarantee that (at least in the models he drew, which I think are basic and almost all inclusive), alcohol thins and keeps the reactants apart, but once evaporated, will have no effect on the cross linked product.
I haven't glassed anything for quite awhile, but I used to glass tubes and fins with regular Bob Smith 30 minute epoxy thinned by around 15-25% to get its consistency thin enough to easily pour and spread thin. Never had an issue with curing, and also was able to spread thin enough that I didn't have to sand it much to get it prepped for priming and painting.