Technical details of epoxy resin please

Hi everyone,

I’m living in India and I’m just starting up my own shaping shack. I’m going to shape in EPS because it is easily available here. So I’m going to be using epoxy. But since the surfboard industry is non existent here I’m having some trouble finding the right resin. Also I want to use only local materials and not import anything. I’m in contact with a company producing epoxy and PU Resin, so they could eventually manufacture custom resin accordingly.

So here is my question:

Can anybody help me and tell me about the chemical details and specifics of epoxy resin used for surfboards? (Density, Viscosity, Flex, Hardness, Geltimes, Chemical composition…)

I read that there is an additive for epoxy a bit like crystic wax for PU that one can mix into the epoxy to make the hotcoat. (easy sanding/gloss finish etc…) What is the chemical name for that?

I would be hugely thankful for any help.

Also what is used for sealing the blank? Is it necessary?

For Laminating I have an AC room, so temperature and humidity should be ok.

I’ll add some fotos of my first board(6’0 x 19" x 2 5/8")…not quite finished yet…no concaves…not yet laminated…

Hi ecmf,


I don’t know about specific resin characteristics but one of the most important features of an epoxy suitable for surfboards, is to be UV resistant.Usually these resins have a blue/purple color in the bucket.

They turn clear when mixed/cure.

The additive you mentioned is optional.You can hotcoat your board without it just fine.

If your board is smooth enough you can skip the sealing process.If not, you can use some lightweight spackling paste.

Tons of info in the forum’s archives.


Good luck!

Hi Windswell!

Thanks for your reply!

I’ve been reading a lot about it in the forums, but haven’t found exact details yet. Btw…I wanna thank everyone for such a great site and so much info on designing, shaping, glassing a.s.o. Swaylocks was such a great discovery! And for someone starting out, like me, it’s a goldmine!

I just got some sample epoxy. Minimum I could order is 4kg! But it’s not blue, it’s more like light lemonade. The company sais it’s UV resistant though. Mixing ratio is 2/1.I’m still waiting for the company’s test report for all the characteristics of the resin. I’ve made some putty with it (because I had some holes in my board from sloppy blank gluing :)…) and it works well. It got really hard. Does the epoxy for surfboards have to stay flexible when fully cured? Gonna try my first glassing job tomorrow hopefuly… YAY!

In the forums I read that one can mix xylene and paraffin at 9/1 and use it as a kind of surfacing agent. But after researching xylene, it seems kind of controversial to use epoxy (no need for mask) and then use a product that is really toxic. Is there something else that would do the same job without the toxicity? Man…as a surfer without chemistry knowlege it’s hard to find my way around all these terms and products. But I’ve learned a lot in the past few months… 

Another question…For making my designs I’ve downloaded a free version of Shape3d. What do you guys use? Is there another good (free) program? Maybe a better one?


If the epoxy is made for composite construction like boatbuilding or whatever, then the epoxy you’ve got is propably good without you needing any particular specs for it. It’s not rocket science.  No need to make a surfacing agent, just sand the epoxy lightly between layers for a good bond. As for UV resistance, as the epoxy yellows it kind of weakens, but not by that much. The blue color is mostly an optical brightner to make it look whiter/brighter, but has little or nothing to do with strength. I doubt that UV would kill a board in the resonable lifetime of it, however it might turn yellow pretty fast and some people don’t like that much. I’d say the best way to protect from yellowing is to use an UV blocking spray coat. If the concerns is mostly cosmetic, adding some pigment might be the ticket.

Most of the surf epoxy companies have website pages that include summaries of the tested specifications for their resins.  You can compare them to each other as well as to the specs for the resin you’re using. They publish some specs, and there’s others available elsewhere I think.

I’m fairly sure nobody’s going to give away their chemistry. I mean, epoxy can only be a number of things though. Epoxide groups on a bunch of carbons and some sort of hardener are sort of necessary. RR is an amine hardener, I believe, I think it says on the bottle. The resin company should have a chemist, no?

Xylene’s not good for you, but, you can use it without killing yourself just fine. Just don’t stand there huffing the vapors. I always wear gloves when handling anything. At least in my experience, epoxy is the more flexible polymer when cured. I have one poly board now, and if it’s dinged it cracks. The ones I’ve shaped with eps just get a dent, no cracking or anything. 


Standard Surfboards epoxy are in général juste slightly flexible than poly, compare young modulus, but it have near double elongation to break that´s way it´s a far better resin. Cure your board in a “dark” hot box, it´ll improve all caracteristics off your resin and it´s sand better. 

wow india?! how are the waves? seen some good footage of sri lanka and some fun small waves in bangladesh (one of my boards has actually been riden in bangladesh!)

board looks damn good and your setup looks professional - are you sure this is #1?

good luck with your epoxy search. like the others said any epoxy will work but surfboard specific will be easier to work with and better cosmetically. probably the closest source for you is australia?


Thanks guys for the replies!

@grasshopper: Actually it’s number 2 to be honest. And thanks for the doubt! That means to me that I didn’t do too bad of a job! I’ve been repairing boards since a long time. But I just started shaping. The first one I didn’t tape off the blank halves when I glued it, so loads of resin spilled on the foam when it dried. I then got loads of holes in the board when peeling off the mess. And it wasn’t glued exactly, so I had to thin it out a lot. And I made a single concave in it just for fun because I was really exited to start shaping (couldn’t hold myself back!). I’ll upload some photos below and that is the very first board I ever attempted of making…The second one (same template and previous Photos), I thought I’ll keep simple because I heard that in the beginning one should try to make some simple boards, so I left it flat.  That’s why my next board is gonna be a 6’4" summer board with lots of volume in the nose, 3" fat and 19" wide (my block is only 19.5" wide) with little tail and nose rocker, kinda boxy rails and flat bottom to slight V in the tail. I hope it’s gonna work out…got the template printed out today. As for the shaping room…I have to be honest…I have never in my life seen one, let alone been in one. I just did my research and you guys helped me out loads with all the tips and photos!!! Also the Father of two friends of mine is a good builder, so he helped out loads. The sidelights are LED and the rack we made out of waste metal bits and pieces and is adjustable in hight and length. The foam on it is an old yoga mat we found on the beach. Right now we are building a dust extractor with water filtering system. I hope it’s gonna work :slight_smile: Waves are pretty good. There are many spots and surfschools are popping up all over. In fact I work at one: check out our youtube channel, just type kallialay surf school in youtube and you can enjoy some of our waves. We also hold an international competition in august called summer swell challenge. All are welcome!!

@lemat: Thanks for the tip! I’ll try that out. In fact my friend who is in construction has some tunnels that might work for that. He cures concrete inside. He adds water, but if we leave it dry it gets really hot and dry in there. But if it gets really hot will the EPS not melt? The Indian sun is strooong… :) 

@drzoidberg: I’ll check it out. Yes the company I’m in contact with has a chemist dr.babu :slight_smile: but since they don’t understand when I say surfboard it’s slightly hard. But I’m sure I’ll get the right mix eventually. I just might have to go meet him personally one day.

@haavard: Thanks. Your comment makes me confident that I’ll manage to make something that works. I’ll keep trying and researching. I’m really exited about doing my first lamination…

Ooooo, sorry my msg got so long…

Alright, cheers!