If you are not using MAS epoxy, you may have amine blush, which is normal for most epoxies and unrelated to the rainstorm. The usual thing is to wash it off with water and a Scotchbrite pad. I Googled amine blush and this was the first thing that came up:

http://www.yachtpaint.com/usa/diy/ask-the-experts/what-is-amine-blush.aspx

I'm using MAS with the slow hander

Did the rain actually get onto uncured epoxy?

Laszlo

   Yeap I had just finished coating it when it the rain came out of no where.

Looks like no one has an answer. My thoughts are that blush is triggered by humidity and that rain directly on the epoxy was enough humidity to overpower the non-blush formula that MAS uses.

If the epoxy has set up and cured, I'd treat it as blush and wash it off the way careybob says. Otherwise, I'd scrape it off and try again.

Good luck,

Laszlo

I had a similar issue once when I left a freshly epoxied boat outside overnight and dew settled on it, leaving behind white patches. I was able to remove these patches by slowing warming them up with a heat gun.

Not sure whether that was the same issue as yours, but it's a simple thing to try before you scrape and sand everything off.

Good luck!

   First let me say thank you for the advice and I will leave you knowing that Dr. pepper you are spot on. once the hull warmed up the following day in the 90 deg. heat it all went away. I did still wash and sand the hull just in case, but Im happy to report its looking great now.

thanks

   I had a similar issue last night. I put down what ihad hoped would be my final coat of epoxy in late afternoon, about 75 outside. by late evening it had mostly set up so I left it out overnight (very big mistake). at midnight I went to check on it and  the whole surface had been covered by dew and was agast to see that and had turned milky white. 

I put it inside, turned on every light and put a fan on it. the temp inside was probably about 70 plus. 

this morning the milkiness had disappeared. I let it bake in the sun all day to ensure it was fully set up. then about 5 this evening I washed it down with a hard bristle brush and warm water. I think that was a necessary step. Do not sand until the wash is done. even if the the milkiness had gone I was pretty sure that some blush had come out or there wouldnt have been the discoloration in the firt place. as I washed the surface i could tell there was resistance about half the time which with a few strokes disappeared. It was almost like a thim film of wax or grease was on the surfact but would come off with a scrub. That was the blush. had I not washed, the next coat of epoxy or varnish would have been a disaster. After the bristle scrub I also went over the whole surface with a clean rag to ensure no resitnce was felt anywhere and that got rid of the extra water. 

My steps were confirmed by a tech guy at MAS whom I contacted today.

I think it is now ready to move on, one day wasted but it could have been much worse. Lesson, watch the humidity, watch the rain and watch the dew. MAS has been great but a non blush epoxy will blush like crazy if put down with a lot of moisture.

David

I feel the pain here and thought I'd share what I've learned about applying epoxy - some paints and the dew point.  First determine the dew point (temperature when condensation occurs) in your shop then avod epoxy and paint when the temp is within 5° of the dew point. Also when working close to the dewpoint keep in mind you want to avoid any temperature change on the work surface - no heat gun or epoxy tools that have been in the freezer. If you're in a warm climate like mine the epoxy should be at shop temperature. My shop isn't air conditioned and I used to keep the epoxy in the house where it's cooler to gain a little working time until one day ....long and ugly story.

  If your shop is air conditioned then your humidity is likely to be low enough not to be an issue. Mine isn't so I check the humidity and determine the dew point before starting work. I use this:   http://www.opticsplanet.com/lock-down-relative-humidity-reader-hygrometer.html  it's cheap and works. The ones at most hardware stores for a few bucks are a joke. The only other tool you need is a thermometer in the shop. The next step is to calculate the dew point. This is an easy tool:  http://www.dpcalc.org/  There is also a good app called 'Dew Point.'

  One last link, this is to a weather site that shows temp and dew point in a graph format. You can see the daily pattern of the dew point in your area and if you work outdoors is all you need. You may need to select your city and enable 'dewpoint'  (customize tab)  http://www.wunderground.com/cgi-bin/findweather/hdfForecast?query=32211

  Hope this saves someone out there some grief.

     The last post was me, guess I took too long ?