Yellow pigment and UV cure

Does anyone know if you can use an opaque yellow pigment and uv cure together. Once exposed will it still cure or should i still add a real small amount of MEKP. thanks


Hi, I haven’t used opaque pigments myself, but what I understand is that they are solid pigments that will impare the UV rays, yellow is quite a light pigment so it should still cure if left out long enough, but it will take a very long time Best to add a little MEKP as well to make sure that the resin cures throughout and not just on the serface.


Use catalyst with the uv when you use pigment. If you don’t, the resin may not cure completely. Why take that chance? I always add cat. to pig uv resin, but I don’t set it off too hot so time is not an issue when I am laminating the board. Mike

Howzit rooster, That’s the way to do it since the sun will kick off the surface resin and the catalyst will take care of whats underneath. This should also keep the resin from draining out of the glass and into the foam.Aloha,Kokua


I’m not surprized you agree. I learned that from one of your post. mike

Psusurf, recently i glassed this surfboard (just hot coated, still needs sanding, do the pinlines, etc…):

I used UV resin on both deck and bottom (almost opaque), but as said before, i also added some merkp, so i’m sure all the resin will cure.

So the trick is just adding a little part of the catalyst you would add with “normal resin”, so you still have A LOT of time to work on your glassing.

I glassed the bottom, taking my time, then exposed the board to the sun, it cured (apparently) in few minutes, i cut the laps, then exposed again to the sun, and repeated the process with the deck.

While, i left the pigmented resin i didn’t use away from sunlight just to see what was the reaction of the merkp on this resin. It took about an hour to gel (maybe a little less) and when i checked some hours later it was hard… so it worked!

I made the same with the hot coat, added a little part of merkp, let the wax raise, exposed the board to sunlight few seconds, let it dry and then i expose the board to sunlight so it becomes completely hard and i can hot coat the other side.

UV resin afford me a LOT of time, and is way easier to work with for us amateur board builders.

hello Kokua,

I read this post as I lately became for some reason more interested in the UV resin and its useability, limits and problems. now you say that the resin could “soak” into the foam if under-catalysed (which would be the case with UV resin where the UV can not do its job) and to prevent this you recommend the additional use of MEKP. this will certainly work, solve the problem and is excellent advice.

but I doubt that the resin can soak into the foam. I think what happens with under accellerated resin is that the glass starts floating and the extra space can not be filled with the resin present, ergo air fills the space. I base this on the observations made when glassing over finbox cutouts which never accumulated a drop of resin except when the cutout had air from the other side (gap in the stringer, foam with open capilars). do you have long term experience with UV resin? I would be interested. we stopped experimenting with it long time ago as it had yellowing and over-reaction problems but that might be history…

Howzit miki, It’s called gravity, if the resin doesn’t cure fast enough the resin drains out of the glass and into the foam. If you’ve laminated the board correctly you use the squeegee to pull the glass tight when wrapping the rails, this is an important step when laminating. Then there’s the resin shrinkage factor as the resin cures to consider. There is no way the glass can float if the board is glassed properly.Aloha,Kokua