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Old 17-10-2012, 12:37   #1
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Epoxy stipling or 'coagulation'

Not sure of what to call this exactly, but I'm trying to coat a piece of philipen mahogany with epoxy (west system)

At first I tried it 'straight' but when it started to set it would clump up and form uneven ridges. after sanding smooth, this picture is a second coat, thinned with acetone so you can see what's happening:

So what am I doing wrong here? Temp is about 68-70 deg using fast hardener.
Am I too thin, not thinned enough????

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Old 17-10-2012, 12:46   #2
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Re: Epoxy stipling or 'coagulation'

I've had the best luck thinning with MEK, thin enough to soak into the wood like water and using slow hardener. I do this 2-3 times until the wood stops soaking it up and walk away. You need to let the MEK gas out while the epoxy cures before laying on a thicker coat of unthinned epoxy.

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Old 17-10-2012, 13:50   #3
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Re: Epoxy stipling or 'coagulation'

So, am I thinking of this backwards? I was thinking it's pooling into high spots. But I guess the low spots are soaking in and the ridges are not?

Thank you for the help though, I'll def. try MEK and slow next time, I'm getting too impatient with this stupid thing.
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Old 17-10-2012, 13:55   #4
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Re: Epoxy stipling or 'coagulation'

Aside from asking if the surface has been cleaned, prepared and dried properly, the next suspect is thinner. Using the wrong thinner will lead to all sorts of problems. I don't know about that particular product, but you should use whatever is recommended for thinning on the can. Another suspect, perhaps, is gelling in the pot. Epoxy can gel very fast if mixed in a container that leaves the liquid epoxy with a low surface area to volume ratio. I would use a slow hardener rather then a fast to help prevent gelling. A trick, based on the fact epoxy reaction ceases at low temperature, is to use two disposable painters cups. 1/4 fill the first with ice, then place the cup containing the epoxy paint on top / inside of that. The low temperature reduces (even stops) the reaction of the epoxy, giving it a much longer pot life. Keeping the cans in the fridge before use also helps, and putting unused paint in the freezer can keep it good for the next coat as well. Good luck!
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Old 17-10-2012, 13:55   #5
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Re: Epoxy stipling or 'coagulation'

From what I see, it looks like your epoxy set before it leveled. I agree with thinning the first layers until you get saturation in the wood surfaces, don't forget to wipe down between layers, sudsy ammonia works well. Definitely use the slow cure hardner.
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