Melting Foam and the Ding Repair Mystery

Hey fellow Swaylockians,

I have a mystery for you. I am doing a ding repair job for a customer of mine and have run in to a little problem. The board had a delam (more of a bubble realy)that I had to cut out and fill. So I went through standard procedure ( I’ve done tons of delams) and noticed that after the first batch of cab/resin fill the hole in the foam had become bigger. The foam had actually melted. At first I thought maybee I ran the batch too hot but it turns out I did’nt. It was a standard mixture/cat ratio and my workroom temp was actually only about 67D if not colder. Originally, when I cut out the delam portion of the board I did notice that there were several melted drip like points stuck into the orig foam. I had never seen this before but at the time thought nothing of it. This board is some custom job that my customer had made about eight ears ago. No brand name or anything, looks almost like a garage job. Do you think it is possible that he used something less tollerant to heat for this board than standard clark. If so, what kind of foam would do that. In addition the board is very yellow all over for its age, and I know the board has not actually been surfed that much or in the sun. It does not have enough dings to be as yellow as it is.

Any help would be much appreciated from the Swaylocks Crew

Thanks Mucho


Howzit Chicksav, If the board was done with epoxy the poly resin is what melted the blank since the two aren't compatable. In over 45 years of working with poly i've never seen it melt a non styro blank.Aloha,Kokua

Ah, I’ll bet I know what the problem is.

It’s an older epoxy/styrene board. It’s not heat, it’s styrene foam dissolving in the styrene monomer that most polyester resins use as a thinner. Some of the polystyrenes look a lot like standard polyurethane Clark foam…but it ain’t. Another hint is the yellowing- the early epoxies, the ones that were really not made for surfboard use, they tended to turn cat-urine yellow with a very little exposure to UV light.

As a test, put a drop or two of uncatalysed resin on top of some of the foam and watch what happens - my guess is it’ll start turning into marshmallow fluff/goo. If you have some straight styrene for thinning resin kicking around the repair shop, use a drop of that instead.

The answer to the problem is to do the ding with epoxy resin. You can use all the other stuff, cabosil and cloth and all, just ya need to change the resin you’re using.

And of course you can guess howcome I know all this… yep, it happened to me too.

hope that’s of use


Yep, I am sure you are right doc. Now I just have to find a place that carries epoxy resin. Does the Home Depot Carry it? I usually get my resin from DMC but thet are closed on Sundays I think. Any advice would be graetly appreciated and thanks again.


Ah; now for the no-fun part that I was just thinking I should have mentioned in that last post.

You see, the epoxy that works for surfboards is kinda rare stuff. I have used System Three SB112, RAKA and Devcon, liked the first two but the third didn’t do real well, trurned the same color as you’re describing while it was going off. I have heard good things about the Resin Research stuff Greg Loehr is making, and I wouldn’t set fire to WEST system cr@p.

And unfortunately, the only stuff you are likely to be able to find easily is Devcon or WEST ( Wildly Exaggerated, Shoddy and Terrible ) resins, say at Home Despot or a marine store.

Might want to call around a little, I know Fiberglass Supply carries System Three, a very few surf shops have some decent epoxy, but as I said it’s not exactly as common as the polyester stuff we’re used to. You have to mix it in exact proportions or else it doesn’t go off at all. Add too much hardener and not only doesn’t it go off faster, it stays gooey forever.

And if they have been giving you wholesale prices for resin, hang on to your hat. The stuff is 2-3 times the price of polyester.

The good news is there are not all that many guys who do epoxy repairs, so once you have some you can have a fair amount of work. The stuff seems to have a better shelf life than polyester too. I have some epoxy more than six years old that goes off as well as it ever did.

Sorry I wasn’t more help



i know poly melts eps but if you covered the eps with a layer (barrier) of something it should shield it from ‘meltdown’, right? would lightweight spackle work? like the type those HDepot blankers use? I thought I saw a thread like this in the archives…I’ll see if I can dig it up. This is just an alternative to using Epoxy as that would be best but maybe this method might work if you can’t find any.


Oh yeah, Greg L’s RR epoxy is great stuff contact him and have it shipped to you. Good luck.

Hey All

Well I checked with Home Depot and lowes But they only had it in small amounts and I need at least a quart. I will get some from Fiberglass Warehouse and let you guys know how it turns out.

Mucho Thanks


Well- I have heard of Elmer’s white glue being used as a barrier coat between polyester resin and styrene foams, painted on like. Haven’t done it myself, but chemically it’s okay ( water based glue, aliphatic resin I think ) , plus relatively impermeable and stronger than the foam.

I suspect the problem with a spackle might be just that, though, that it’s going to be permeable enough to let styrene and various byproducts of the polyester resin going off , well, it’d maybe get into the foam and then you’d have the same thing happening again.

My understanding of spackle use on styrene foam boards is that it’s to prevent too much resin from going into the nooks and crannies of the polystyrene foam but not so much that it prevents the resin from contacting and making a good mechanical bond with the foam. Plus it’s not a very strong material, so that the delam problem might happen all over again.

hope that’s of use


Howzit doc, the Elmers glue works good, the trick is to apply 2 coats letting it dry between coats and making sure all the styro in covered.Aloha,Kokua
Howzit Chicksav, Where you live you are surrounded by surfboard factories and probably suppliers also or take a drive to BAsham's in San Clemente and get what you need. I definitly woudn't jump the gun and buy the wrong epoxy because you are in a hurry so if you must wait til Monday then just wait.Aloha,Kokua

Your right guys,

I don’t have to have it today so I will just wait until I can get the good stuff. I have several distributors within a 50 mile radius here in SD I was just hoping to score some today. But, like with surf, patience always rewarded and I am sure I can get some from somewhere around here. By the way, speaking of Elmers. I was in Lowes and noticed they caryy a 2 part epoxy resin kit made by elmers. It comes with a six ounce resin and six ounce cat container. Might work great for those smaller jobs. It is 15$ though.

Take care and thanks again to Doc and Kokua



I want to repair a epoxy- surftech surfboard, that is nearly broken in two parts. Well the foam has a gap and I have to glue it together and fill the gap.

Using epoxy and microballoons seems to be too rigid and hard, so that by flexing the board, the glued part will break again.

Do you guys have any idea what kind of Glue or liquid foam (2 comp resin that expands by catalysing) is the best for that kind of work?

thanks for the help!