Poly over Epoxy

New year hasnt started well, due to a short supply of epoxy i thought i would hot coat and gloss with poly…

The stuff in the pot kicked as usual in about 12-15 mins but the coat on the board failed to kick and was still wet 3 days later. When i pushed my finger in i could actually move the glass. Also, the one bit which did kick was a 3" patch in the centre of the deck, but it went kind of blistery and horrible. Tried scraping of and cleaning with acetone but laminate was beyond resonable repair. Very Gutted many hours gone into this board now its scrap.

Does anyone have any words of wisdom on this subject.

By the way it was a balsa over eps, workshop temp cold


Was the epoxy hard when you sanded before the poly coat? What type of epoxy?


Epoxy was just a marine epoxy, RR to expensive to ship over. Never had any problems with it before 90% of my boards have this epoxy…

The epoxy was hard prior to poly coat.


I was making a wooden fin years back and had some tabletop epoxy that I used to glass the wood. When I tried to glass it onto the board, (using poly resin) it never kicked! I just pulled it off and used other fins. Anyway, my point is that not all epoxies work with poly resin, sounds like your experience was like mine (only much, much worse). Chalk it up to work experience, that’s all part of surfboard making, just when you think you’ve got all the angles figured, it throws you a curveball. Good luck on future projects!

Cheers friend , your probably right chalk it up to expierience and try again. Think ill stick with epoxy from now on.

Sounds like an incompatability issue, indeed. I poly glossed an epoxy laminated balsa board for PierreB, who posts here, and the gloss set, and then the lamination went soft under it. Started in just a couple of quarter sized spots, and then spread. Areas that were hard enough to sand and polish went completely mushy after a few days. It’s the strangest damned thing I’ve seen in my experience building boards. Quite a shame, it was probably the nicest polish I’ve managed to turn out.

Needless to say, I’ve since changed to expoxies (to RR) and haven’t had any compatablity issues since.

Thanks, RR it is then.

sorry to heard about your luck. how cold was your shop? you can heat your epoxy and you can heat your poly, but the room temp. has to be warm also. resin research is the only way to go. poly over epoxy is very touchy,it can be done but everything has to be just right. the best way to go is full R.R. epoxy,this epoxy is made for surfboards and for all types of temp. good luck and happy new year. Ed(ET)Townes soulmanet@yahoo.com

Yeah shop was pretty cold, probably around 6 degrees. Looks like RR is the only way to go.

yea,it needs to be around 55 degrees. Ed(ET)Townes

Not sure if the poly didn’t go off or the epoxy. If it’s the epoxy then you’re pretty much stuffed. If it’s the poly, mix a new hotter batch and brush over the old poly. Should cure the poly underneath. Polyester eats polystyrene too so be careful.

Probably should of tried that before i binned the board… oh well live and learn. Cheers for advice.