Hi all, I bought a bag of sun cure powder and mixed up half a litre of it. Its GREAT stuff for doing patches where I burned through etc, saves waiting until the next day to sand it, now that we have a bit of sun in the UK at last! Brilliant stuff. I am wondering about mixing up a batch of it and using that batch for hot coats, but its really hard to get my board outside when its wet (very narrow door which means tilting board on its side, not good for runny resin!), so I am considering using sun cure resin WITH about 0.8-1% of MEKP in it as well, maybe even on lamination but especially on hot coat. That way, I can wait until it kicks from the MEKP (heater turned up once finished) and then take it out in the sun to cure it nice and hard in 10-20 minutes ready to sand and move on.
Does that sound ok or is it not wise to mix MEKP with sun cure powder?
thanks
Hi Helter. You can use mekp with your sun cure. Sounds like a reasonable plan. I do it all the time. Mike
Cool thanks v much
Don’t take this the wrong way but you do know there is a search function correct? The mass majority of the info you seek is all there. Dig, search, dig more, compile the info, go read more. Make connections, it’s all there.
Again, not a shot at you, just an observation.
No offence taken 
I think the incredible amount of stuff that’s been discussed on here over the many years could suggest that no further discussion is ever needed as everything has been covered more than once, sometimes 10 times! I notice though that every thread i find when I search (and i do search) is usually 7-10 years old, and stuff changes so fast with technology, surfing ideas, and materials, that I feel safer asking for current opinions. Point taken though and on this point I didn’t search so I will gently wrap my knuckles! all good, thanks
add catalyst to your UV resin when doing tinted/pigmented laminations, for finbox/leash plug installations, resin panels, and sanding coats. also if adding q-cell or cabosil.
and you might as well kick the resin with 2% catalyst for hotcoats. it will set up faster and will help prevent sheeting on the rails.
Thanks. What’s sheeting? is that where it sags and creates visible lines as it moves before curing?
What folks throughout other parts of the planet call a “filler” coat ; is called a “Hotcoat” in the U.S. It is called such because it is catalyzed hotter(more or hotter% MEK). It also contains a “Wax Solution” that when used properly makes sanding said filler coat easier. Lam resin stays tacky. A typical Hot Coat of 1 quart would would have added to it a cap or two full of Styrene Wax Solution and 10 cc MEK. This will cause the resin to set fast and not slide around on the surface, but it also is slow enough that the wax in the Styrene Solution has time to rise to the surface which is key for sandability. Putting a SMALL amount of MEK in a Hot Coat defeats the purpose. People who use MEK with UV powder are of the nervous and untrusting type. They are fearful that the UVPowder won’t do its job. When you UV a Hot Coat you should walk the board outside and count to 10 or 20. Then walk the board inside, set in on the rack and leave it awhile. If a few minutes you should start to see a “cloudy” or “oil on water” type effect in the resin. After 10 or 20 minutes walk it back outside and leave it until hard. Simple as that. The count of 10 or 20 activates the UV process. Putting the board back inside out of UV reach, slows the process down enough to let the wax rise. Once it appears to have done that; back out in the UV to harden. Lam coats in UV are different. Walk them outside and leave them until hardened. I usually put my UV powder in my resin the nite before. Stir really good and leave over nite. Next day when ready for use; I add my Styrene Wax Solution and stir really well. The overnight time allows the UV Powder to dissolve a little better. Otherwise you will have little “sugar” crystals throughout your nicely brushed on Hotcoats. Always store UV Resin where the UV’s can’t get to it. Under your beach towel, in an old ice chest etc. some place that is out of UV. Hope you comprende all this and it’s kokua. Lowel
Mucho Kokua, thank you.
Some great tips there. I actually mixed up a batch of resin with UV catalyst and keep it in a tub away from UV (and in a black bin liner to be extra safe).
You hit the nail on the head re “untrusting”. I am exactly that, first time user of UV and when I typed that I was a bit concerned it might not work! I have seen it in action now (repairs) and its amazing stuff. I love the fact you can seriously speed up the process (when sun is shining!). Like you, I mix the wax in styrene to order, the resin is pure lam resin with UV catalyst when stored.
Filler coat - yes I thought that was just another term some use for hotcoat. Glad you said it though, as with the incredible amount of resin I am using due to consistently burning through (only a few patches, but patching over never works, so i sand it all and resin again, I know I know, crazy probably, but I want a perfect finish and patches just seem to stay visible!). I did WONDER if filler coat was a coat of lam resin over the lam and before the hot coat. I know nobody does that, but I was starting to consider it. It would prevent my burn throughs and speed up my terrible process hugely! I know the real trick is to learn to sand properly (perhaps not be in such a hurry!) but until I master that, maybe a very thin coat of lam resin before the hot coat could give me a bit more leeway with my monster sanding technique 
I like to add 2% cat to my UV resin for hotcoats. I let the hot coat go off, which usually takes about 10 mins, peel the tape of the rails right as the drips start to gel and then stick it in the sun to cure it up nice and fast. This way you dont have to pick up a board with liquid resin on it which can cause issues.
Yes, exactly.
That’s exactly what I was hoping to do. 2% it is then, thanks all
PS, am I right in thinking there are no other effects of using sun cure instead of MEKP, no discolouration issues or delam issues, just same as normal resin?
PPS - I noticed it gets DAMN HOT! I put a cup with a tiny bit of suncure resin in bottom, and it melted the cup! I won’t use it for anything like sockets (obviously) but do you take any precautions due to the thermic reaction?
Yes you can do what is called a “Cheater Coat”. Lam resin squeeged on after you finish your lamination. This is done before the lam coat even gets tacky.
Ah, so THAT’s what a cheater coat is!! Cool thanks. Just curious, does it need to be done like that (after lam before cure) or is that just how people do it to save time and another step?
To keep exotherm down yes, be careful about having large quantities of catalysed resin.
The melting cup was more likely due to the solvents in the resin. Polyester resin (actually it’s more the styrene it contains) will eat through cups unless they are paper/cardboard (not waxed!) or a solvent-resistant material like polypropylene or polyethylene.
Thanks, yes this is solvent proof, it wasn’t chemical melt it was definitely heat. I picked it up and jumped 6 feet in the air! I had no idea the exothermic properties were THAT big!
For sure.
It can catch fire if you really push it.
Although these days I’m mostly an epoxy guy, I sure do love the smell of styrene in the morning.