Yellow stains during epoxy glassing...

I noticed mention of this in another thread but I thought it deserved its own thread to avoid a tangent.

I’ve done about 30 epoxy glass jobs now and on many/most of them I can’t seem to avoid getting splotchy yellow stains in the glass during the lamination process.

I use vinyl gloves (from Harbor Freight). Greg L. recommends vinyl gloves in his DVD.

I also use yellow plastic epoxy spreaders. I thought it might be the spreaders leaving the stains, but now I’m not so sure.

I use RR Kwik Kick and laminate in a controlled room temp environment.

Anyone else have this problem?

i have found it to be a result of the epoxy reacting with the oil or sweat off the hands. i noticed it from handling probox fin jigs and boxes. went like fluorescent yellow. i’m even careful now with taken gloves out of the box not to touch them on the outside too much. since i have tweaked it, i have never had the issue again. only ever touch an unfinished board with gloves on also, bit like a crime scene!

Correct.  too much hardnr will make it yellwo and be rubbery. Adding too much pigment will make it be rubbery too.

I sometimes get yellow stains but it pretty much an age thing.... and all the damage I have done to my prostate

"I also like to add a tiny bit extra hardener to my epoxy, so if I mess up my mixing ratios, everything still cures."

Adding too much hardener can cause the cured epoxy to be rubbery.  Best to just stick with recommended ratios - either by weight or volume.  Stir thoroughly and keep everything within the recommended temperature range... maybe ramp up to a post cure within the recommended time frame for maximum physical properties.

If you do this you will minimize your chances of failure. If you deviate and start eyeballing your ratios to compensate, you'll likely end up with problems.  I say this not to be critical but to hopefully prevent newbies from going down that road.  Unfortunately epoxy is different from polyester where an additional shot of catalyst can help 'speed things up' on a cold day.


I think it could be excess hardener not being used to harden and dripping down and staining the foam. I only say this because the yellow-brownish stains I got on my one and only epoxy glass job were roughly the same yellow-brown that West system epoxy hardener is. I also like to add a tiny bit extra hardener to my epoxy, so if I mess up my mixing ratios, everything still cures. Probly wont use epoxy again for a long long time, so good luck figuring this out.

Thanks everyone for all of the diagnoses. I am hoping its the gloves. I will try different ones next time and see if that solves the problem. This has happened to me with nearly every board. Just little yellow splotches here and there. Sometimes alot, sometimes only one or two. Happens only in the lamination, not the hot coat. My resin is pretty new. Less than a month old from Greenlight and I’m pretty sure they go through it pretty quickly so it’s not sitting around there too long.

I’ll update back when I do the next glass job with new gloves…




I’d rather you didin’t go all negative towards my choice of spending a little extra money on my squeegee of choice. The comfort in knowing I don’t use squeegee’s that need special pre treatment before use and have no chance of bleeding color is worth it to me.


P.S. ResinHeads :   " Most don’t run… They do laugh though"    was outstanding…

Weigh your mixtures, check gloves and squeegees for bleed (acetone on paper towel), try sealing with epoxy Q-cell slurry, and don’t use your gloved hands for lapping rails. 

Here’s some real yellow stains:

Old epoxy will yellow I dont care what brand it is. The containers should have dates on them like milk.

I know exactly what you are talking about. I get it from time to time.   i can do two boards side by side and get an issue with one, but not the other?

Most of the time it happens when I rush to mix a second batch of epoxy. Sometimes not mixing excatly to proper ratios does it.....sometimes it's using slightly old epoxy, sometimes its an issue of WTF?    i did a 9 ft long board a few months ago, perfect color job the bottom is all yellow and F'd up, while the top is pristine and white.   I used CE on the top, and KK on the bottom.

I have also had  gloves do wierd shit when epoxy gets on not to let the gloves touch epoxy or the board. Spreaders, they usually don't bleed?  I've used all kinds of cheap spreaders....blonds, brunettes, red heads.. etc.  but most don't run...they do laugh though.

Try mixing you stuff better, limit the spackle, don't touch the board with the gloves, use fresh epoxy. and you should do better.


 To check your new yellow squeegee for bleeding you take your gloved hand and spread less than 5cc of the mixed up epoxy on your yellow helper.  make sure to get both sides.

Now take a clean white rag or your fiberglass off cuts and firmly wipe “old yellow” off. Now look at your white off cuts and if there is yellow dye on the rag, repeat above step one more time.  Your squeegee should be good to go.

I wouldn’t use the bondo brand because it is too expensive. If you are glassing lots of boards just buy a box of the 6 or 8 inch yellow type. The current brand I have don’t bleed yellow, but you only know if you check out as described above.

Wipe old yellow off nicely and it should last for dozens of glass jobs.

The spreaders I use are from US Composites. Here on the bottom of the page (they are yellow):

Lately I have been lightly sanding the spreaders and cleaning them with DNA before use to see if it’s on the surface. Still have a problem.

I am thinking it’s the gloves. I’ll try some different ones and see how it goes…


The 3M Dynatron spreaders that I use do bleed some color when new. A solvent rub before the first use solves the problem.

I use the Bondo brand of squeegee that comes a package containing three different sized squeeegees. They are a light tan beige in color and absolutly do not bleed any color into the glass job. You can buy them at any automotive supply store.

I have no experience with the yellow squeegee you refer to but I have experienced  gloves that yellow and stain from touching epoxy.

I now use the blue nitrile gloves, the are very resistant to chepmicals of all kinds.

Also if you’re sealing a EPS core with drywall spackle and thinning it , use distilled water, the minerals in tap water can cause yellowing. Some guys thin the spackle with DNA for this reason plus faster drying time.

Change your squeegee brand and see if the problem stops, if not change your gloves and check again.

Watch where and how you store your fiberglass. It can pick up contaminates