Bumpy epoxy cure - amine blush with MAS??

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Bumpy epoxy cure - amine blush with MAS??

Postby Creekboater on Tue Jan 09, 2024 3:19 pm

I see this from time to time. After an initial coat of unthickened epoxy onto raw wood, I sand and roll on another thin coat of unthickened expoxy. And after it cures it looks to be 'beaded up' as if water on Rain-Ex. I might guess this could be due to amine blush but I'm using the MAS non-blush system.

See pic below. I'd appreciate any insight anyone might have...
Attachments
bumpy1.jpg
bumpy1.jpg (180.25 KiB) Viewed 12499 times
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Re: Bumpy epoxy cure - amine blush with MAS??

Postby [email protected] on Tue Jan 09, 2024 6:11 pm

On my first build I often used isopropyl alcohol (90%) to wipe down the first coat of epoxy after sending,
and the second coat often went on lumpy. For my Pocketship build, I switched to denatured alcohol (from the hardware store),
and that problem went away. I particularly remember epoxying the spars, and how nice and smooth each coat of epoxy went on.

Also, you might be laying on the second coat a little too thick.

Doug
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Re: Bumpy epoxy cure - amine blush with MAS??

Postby dbeck on Wed Jan 10, 2024 4:27 am

Maybe this does not depend on the brand. We are not using MAS but PEC, which came with our kit from fyneboats.

We have seen this from time to time. I tend to say this happened to us when working at colder temperatures around 60 degree F [1].

Dietrich

[1] CLC recommends temperatures above 60 degree F, better 65-75 degree F, and removing blush with warm water, see here.
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Re: Bumpy epoxy cure - amine blush with MAS??

Postby Creekboater on Wed Jan 10, 2024 9:39 am

Thanks Doug and Dietrich.

My inquiry really is whether others are seeing a blush with the MAS non-blush system. I am seeing blushing and, if I don't notice it and clean it before the second coat, then the picture I sent is what I get after curing. If I notice the blush, water works just fine to get the blush off. In that instance, I do not see the bumpiness on my second epoxy coat. I'm just frustrated with MAS and curious if anyone else is seeing this.

My shop is conditioned at 70-80 F , humidity 45% or so, no motor exhaust, etc. etc. so environmental conditions shouldn't be a factor.

My thought is I've gotten my hands on a 'bad batch' of hardener or resin or both.
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