Hi guys,
Been skinning for quite a while but now I've stumbled onto something new. I was doing a pair of doorsills using 400 gsm cloth. I applied the first coat letting it go to a full cure and then applied the 2nd coat ( epoxy laminating resin + fast type hardner) with sanding cause I felt the first layer may have been too thin.

2nd coat went for a full cure and then I started wetsanding it ( 400 grid ) After getting it all even, I saw white marks all over the panels, nothing new but this time they remain visible :-( Wiped it down with acetone but even then I can still see them .. Do I need to sand down even more or did something go wrong here ? Please advise :-)

Sounds to me like you got amine blush "trapped" under the second coat ... but since you let it cure fully and sanded the first coat, that sounds like the first coat did not in fact cure fully?

What kind of temperatures are you working in ? (This is a very humid winter!!, unless you are on the southern hemisphere .. )

"Sapere Aude"... Dare to KNOW!

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Do not adjust our mind, theres a fault in reality :-)

As dravis says, the first layer may not have been fully cured.  This time of year the lower temperatures and high humidity can play havoc with epoxies. We always recommend working above 20C (measured) and avoiding damp environments.  Sheds/garages in winter can be much damper and cooler than it seems.

You may well have to sand right back to the first layer to get rid of it.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

I'm working indoors with a constant temp around 22 degrees.

I would tend to agree, but the first layer was fully cured (24h), and I didn't sand it.

Before wetsanding the white haze also was not visible at all ...

Okay, seems to be something wrong with the 2nd layer. Went crazy on the parts with an 80 grid, till it almost hit thecloth, worked slowly upward to 400 again and the white haze now seems to be gone ... will require a lot more elbow grease but they'll turn out fine eventually :-)

Not sure on what went wrong though .. don't think I screwed up the mixing ratios .. oh well, all well ends well

I would tend to agree, but the first layer was fully cured (24h), and I didn't sand it.

Ahhh .. there's the problem ...  You did not sand or "key" the first fully cured coat of epoxy...

While a very pure epoxy like the EC coating stuff, will bond very well to itself, even with no sanding or keying, this is not the case with most laminating epoxies.

What you probably had then was unbonded areas under the second coat ... only cure is to sand through it ..

Good luck with the new coatings,,,



"Sapere Aude"... Dare to KNOW!

The written word is the only truly efficient vehicle for transmitting a complex concept from mind to mind...

103% of all people do not understand statistics...

Do not adjust our mind, theres a fault in reality :-)

Never had a problem before doing it that way, but I always used West Systems before.. ah well, gonna take the advice and give every fully cured layer a good sand from now on thanks

An even better way: don't let the first layer cure fully before applying subsequent layers. This will create a chemical bond.