Yellow bloches with Epoxy


I have just laminated my first board with epoxy SP 115 and some yellow blotches are showing up after about 2 weeks (still in shaping bay) Any one else have seen this? Whats gone wrong? The blotches are a bit urine yellow and not pretty!

Hmm not too happy


I’ve also noticed this.

My first epoxy board was laminated in August with RR epoxy and on the hull there is a small of light yellow.

Anybody have any answers


the yello squeege/spreader thing bleeding? maybe?

does it look like a finger print, I know with poly if you get acetone on sone types of glove and touch the blank you will get a yellow/brown mark, that you cant see before glassing, as your using epoxy there shouldn’t be any need for acetone though, and I’ve not seen this happen with DNA.

Lots of prope have had problems with those yellow squeeges, I dont use them atall, I just cut one to size from a piece of white mount board works great for me and I canget about 30 from onsheet of the suff, thats about 3p each.

Here is a photo of what I mean, I’m not sure what you have said, is the case here. I might get in touch with SP Systems to see what they say!

Thanks, still interested if anyone know what it might be!


Is it the stringer bleeding/gassing out. Could be wood oils…

Does it follow a pattern, near the stringer…

Epoxy takes time to set, things flow, just a possibility…

No stringer on the board! No pattern! Just random big/small blotches that look a bit like peeing in the snow! There is a window with some sunlight coming through, I wonder if the uv is dodgy!? I didn’t seal the blank so could be gassing of the foam perhaps!?

Hey woody,

What’s “white mount board”?

The stuff you make your squeegees from?

Any other names I might know it by?

I’m sick of cleaning my yellow ones, I alaways forget and end up scraping off dry resin…


What’s that red line below, it just looks like the stain is following the line…

Do the marks follow the sun pattern that came in…

The red line is the lapline but they don’t really seem to follow that as they are spread out over the board randomly, although seamingly only the top where there is no paint (acrylic) but that can be because I can’t see it where the paint is. The sun covers the whole board at one point through the day so there must be something fishey about the affected area.



I have seen this on two epoxy boards that were less then a month old. One I dripped some water (like a drop or two) from a painting sponge that I had just cleaned some orange acrylic paint off of. You couldn’t tell when it first dripped as the water looked clear. It grew and spread and discolored. The other time I was taping off a blank to paint and I can only imagine it was sweat or something that must have reacted with the spackle.

KKSurf not sure what you’d call it, but its basicaly 2mm rigid card, smooth faced on both sides, used for the mounts on picture frames. It comes in A1 sizes and in many colours but I use white and cut it in to 5"x8" peices, I can use each one 2 or 3 times as long as I wipe them after with a piece of kitchen towl.

You should find the stuff in any decent art shop or a place that frames pictures, they may also sell ideal sized off cuts cheap.

Looks to me like the paint got re-activated by the resin, and when you lapped and pulled resin over the tape, it pulled some paint with it. Because there’s no paint right along the lap line, the tape seemed to stop the paint, but once across the tape, the resin/paint mixture shows up.

Try sanding it off.