Yellowing of epoxy- eps boards

I have made a few EPS/epoxy boards and they always yellow quick. After a few months they look years old. I’ve even used reisn tints to color the epoxy and noticed yellowing around the lap lines , or around glassed on fins. Is this a result of something I’m doing wrong or is it just the nature of the beast?

What brand of epoxy are you using? Not all epoxies are the same, some are much

worse than others.

Why don’t you paint them on the outside, like windsurf boards and Surftechs, and epoxy Bics?

White is a good color.

I had that problem with WEST system, but now use a locally mixed formula which shows no sign of yellowing. You could try Woodenboat magazine, there are a lot of different epoxies advertised there.

Check out his test of different epoxies. http://www.oneoceankayaks.com/Epoxtest.htm Some yellow alot, some don’t. They have a sample of west epoxy in the local boatshop, a big yellow chunk of resin… Did you cover the epoxy with something with a UV filter?

regards,

Håvard

Oh Great… very interesting site… I’ve just used West 206. Better get some 2 pac.

Hicksy

Quote:

Check out his test of different epoxies. http://www.oneoceankayaks.com/Epoxtest.htm Some yellow alot, some don’t. They have a sample of west epoxy in the local boatshop, a big yellow chunk of resin… Did you cover the epoxy with something with a UV filter?

regards,

Håvard

That site was very interesting. I found this info there, has anyone tried this cleanup method?

 <span style="font-size:6px">Epoxy Cleanup  <img src="http://www.oneoceankayaks.com/Images/yellodot.gif" alt="" class="bb-image" />

Most people clean epoxy with thinners such as acetone. Because of its toxicity, expense, and fire potential, I try to limit its usage only for cleanup and soaking of brushes or tools that are used immediately. Since epoxies are fundamentally alkaline, (like lye-sodium hydroxide or baking soda-sodium bicarbonate), they can be neutralized by acids such as vinegar. While acetone thins the epoxy (when it evaporates, a sticky film remains) vinegar neutralizes the epoxy completely and with it its toxicity (new chemical is formed, no epoxy remains). Vinegar is cheap non flammable and removes uncured epoxy completely. Because of its acidity, don’t use it to clean the hull or surfaces to be re-coated!

maybe greg can help us with that question? or bert

Hicksy, I used West system for 9 years, and found that if you polish your board with a good car polish, it will make a tremendous difference. I had boards on roof racks and lying around in the paddock. Only those which were not polished showed signs of deterioration. I have written to Tim at Gemco here to see if he can supply over your way. Tim makes 4 to 1, and 2 to 1 epoxies which are blush free, don’t yellow and have excellent air release (bubbles disappear). The resin is a little slow but is nice to use and is lower in toxicity than West.

I have a 2-yr old Loehr design epoxy… Used regularly. No yellow yet. I think the older ones yellowed pretty quick, tho.

I use System 3 SB112 on my balsa boards. This has an added UV inhibitor but is a bit on the expensive side ($82 for a 3 qt 2:1 kit from ‘fb supply’) but very easy to use. No problems thus far with blush, yellowing, etc.

I use xylene to thin it out (when needed) but never to clean my skin. Vinegar will remove uncured epoxy from skin (note: I wear gloves and attempt to avoid all skin contact as much as possible).

The first time I tried to clean a good, very expensive, brush I had used for a gloss coat, it turned into a big jelled mess! I am strictly a throwaway brush type now.

Xylene did, however, do a good job in cleaning my rubber squeegee!

Interestingly enough, although xylene and acetone are both toxic, they also both occur naturally in the environment. We are exposed to them in minute traces all the time without even knowing it. Their cancer causing potential is relatively unknown.

For more info on acetone, xylene, and other hazardous chemicals go to:

www.atsdr.cdc.gov/toxfaq-z.html

Hicksy, if you are interested in Gemco epoxy, Tim says that they have an agent in Melbourne. Also they can ship to you directly http://www.gemco.net.nz/

Cheers, Roy

Thanks again Roy, you’re a fountain of information. I’ll check them out for my next project.

Hicksy

We have tested most of the usual epoxies and polyesters used in boards for UV stability. Of all the ones we’ve used, Resin Research and Fiberglass Hawaii were the best and pretty much equal against yellowing. Both were also equal to or better than polyesters to yellowing. Systems Three SB112 was next followed by SP Systems 115. The boat epoxies were all generally terrible.

For use on urethane foam you must include a UV absorber. We have this available as an additive and SP 115 already includes this in their system. This only protects the foam from UV, not the resin. Most of the polyesters made for surfboards also include UV absorbers but they generally don’t have enough to really do the whole job. This is why you see polyester boards yellowing at the rates they do. We don’t feel UV absorbers are a nessasary component in boards built with polystyrene foam so we don’t include them plus we have reservations about unnessasary additives. There was also a question of, “Am I doing something wrong”. This is possible. A bad mix will yellow faster. Always stick to the suggested mix ratios and be sure to mix thoroughly.

Uh oh… I JUST laminated (and have one side hotcoated) using RR epoxy over a Clark blank. I didn’t use any UV absorber. Guess I’ll be living with a yellow board soon? DOH! I’ve followed your posts, Greg but don’t remember seeing that before.

I only recently learned that you could even use epoxy over urethane. I always (for 30 years or so) thought that since polyester resin melted EPS, epoxy must melt urethane.

Quote:

Uh oh… I JUST laminated (and have one side hotcoated) using RR epoxy over a Clark blank. I didn’t use any UV absorber. Guess I’ll be living with a yellow board soon? DOH! I’ve followed your posts, Greg but don’t remember seeing that before.

I dont think so.

I have a 6’8" laminated with RR epoxy and another board laminated about a week before using poly and the epoxy board is whiter than the polyester laminated board.

I had a pile of “bones” from outline cuts that I left outside. I swear, they start turning dark within hours if left in direct sun. In a few days, they get really dark. I even noticed the blank I was working on would darken slightly in direct sun if I took a break. It wasn’t very noticeable until I returned to shaping and started seeing whiter foam where I was working. I can see where it probably isn’t the resin so much as the foam.

John, was this with clark foam or eps? I also suspect the spackle I used to coat the blanks may be whats turning them yellow so fast. (Fast being 6-8 months) The part that has me baffled is the yellowing I’m getting around a blue opaque bottom where the top free lap edge is. This edge was differently not visible at all when the board was new. I used Gregs epoxy and had no trouble at all during lamination. But as he said, maybe I had the mixture ratio a little off or did not mix it well enough.

The board I’m glassing and the bones that turned dark are all Clark foam. No Spackle used. I think it was Noodle who suggested using only distilled water to mix spackle (if it wasn’t pre-mix) as minerals in the Spackle could cause discoloration.

Search shows it was Noodle. He offers some other tips on Spackle. He was one of the most helpful guys on epoxy before Greg Loehr…

http://www.swaylocks.com/forum/gforum.cgi?post=105008;search_string=distilled%20water;#105008