Air bubbles in hotcoat

When I’m stirring my resin/catalyst for the hotcoat, I end up with tons of tiny airbubbles in the bucket. As soon as I brush the hotcoat on, it looks like all those bubbles end up on the blank and then I get a million little divits in the hotcoat when it’s cured…Any way around that? On a tint it sure makes everything look crappy…I figure you can’t really stir it slower because it’s already starting to kick right? What’s the secret??

Ahm, amigo, just how cold is that resin before you stir in the catalyst?

How cold is it?? I have no idea. It is stored in the metal 1 gallon container it came in, on a shelf in my garage in San Diego. I would gess it’s probably about 70 degrees???

Ok, cold resin would tend to keep those bubbles longer.

Couple of possibilities - you may want to add a little less catalyst, so the bubbles have time to work their way out, and you might want to use a different stirring method, so that you don’t wind up with so many bubbles in the basic batch? I usually use something like a paint stirring stick, slowly, which seems to work for me.

hope that’s of use



Stir slowly.

Any decent resin batch gives you at least 15 minute working time. Takes about 2 minutes to brush a hotcoat on.

Takes about 5 minutes to do a good lam job.

Try a timer, so you know how much time you got left

Hey Ten Over,

I’m in SD too, 70 degrees, 1 qt of resin, about 10 cc of catalyst + - should do the trick, gives about errr, 20 min of work time, use 15 cc and get about 15 mins. The hotter you make it the more chance of air pins to chemically react. Make sure the board, resin, catalyst, and room are all the same temp. Brush it on to cover board, go side to side, and tip to tail twice, once around the tape edge…walk away. shouldn’t take more than 5 mins. The bubbles & brush marks will level out, in about 10 mins. Put stuff away, clean your brush, and gear just in time to pull the tape.


Oh yeah, thats what gloss is for! fills the tiny white holes.

If the gloss will fill fill those holes, then I’m not too worried, as I plan on going gloss on most, if not all, of my boards. If the bubbles are there after the hotcoat, and you sand the hotcoat, all the bubbles fill with dust and turn white (I’m making tinited boards)…Will the white dissappear when the gloss is put on?

Yep most of the little white holes will fill with gloss and turn clear, so will all the little sand throughs. You have to becareful, some of the holes will only get the most tippy tops exposed and end up filling a bigger hole with dust, thus making it almost impossible for the resin to fill and saturate the sanding dust and incapsulating the white bubble. How to tell if it will fill up? Wipe the board down with Acetone before you gloss, if the holes disappear when you wipe, and then reappear when it dries, no problem. I also use a fine peice of metal string (guitar string) to poke the resin into those tiny nagging white holes usually around the rail tape line, the metal string is strong enough to bust the thin top of the resin shell of the pin hole and help fill it with resin. Come to think of it I’ve used it for some bigger holes in this way to. Anyhow if you need help I’m in town and am will to help out


I use my air compressor with a needle on it… for basketballs etc. Crank it up to about 70-80 psi. No more powder.

Tenover, I also found another way to help get rid of those pesky bubbles. If it’s cool outside, I heat up the resin before I add the catalyst. Just a little. If the sun is out, I’ll loosen the cap on the gallon can, so air can escape , wrap the can in black plastic, and set it outside for 20 minutes. As it heats up, it gets thinner and the bubbles rise quickly. If I’m indoors, a 500 watt light aimed at the bucket with resin will do the trick. Some bubbles will get in when you stir the catalyst, but they’ll rise quicker if the resin is warmer than room temp. Doug

resinhead- Check your PMs.

Good tip Doug…Thanks.

Hey resinhead-

Your name, by chance, isn’t Paul is it?

Actually my name is Jay Mickelsen.

Most of those “little white holes” are actually chunks of wax from the surfacing agent.If you bought premixed hotcoat resin it may be the problem.If you added your own surfacing agent try warming it up and shaking it before adding it to the resin.This is a perfect example of why modern sanded finishes are inferior.Glossing is an integral part of the system,if you cut that corner you have a weak board.We started doing sanded finishes back in the early seventies but we glossed them first.The weight was negligible…it was the flat finish we were after.The industry pushes these cheap solutions to “save weight”…bullhocky…“save money” is more like it.An acrylic speedspray will help somewhat in the sealing department but it adds no strength.That will be 2cents…cash please.

Hmmmm…That makes sense. I bought the stuff pre-mixed, but it was from a reputable “dealer” who does alot of business selling glassing supplies. I wonder…On another note, I think I just screwed up the board totally. The hotcoat came out a little bumpy, and with those pin holes. It’s cured for over 24 hours, but when I broke out the orbital and started sanding it with 80 grit, it kind of gummed up the pad and the board…Not sure if the wax didn’t rise or if that’s normal or what…? The board was pretty much a “test” board anyways, but it WAS for my daughter so I’ll have to make another one if it is trashed. For starters, the “board” was shaped from soft foam used from an old longboard and ther were hills and valleys all over the place, so I should’ve made sure the shaped blank was nice and straight everywhere before I even STARTED glassing, but hey, I was excited and ready to charge into glassing (Which I like alot more than shaping so far). You live and learn I guess. I’m so amped on the whole process though, that I’ll probably strip the other half of that board and make her a little “mini” fish or something, maybe like a 4’0"…Make it really clean and straight so the glassing goes like it should. I had no problems with doing the tint and getting a pretty good, even color distribution, and the cutlaps were fun and challenging and turned out very well considering it was my forst attempt. The hotcoat seems to be what really screwed me up…

Don’t go thrashing it yet! You can re-hotcoat and sand the whole thing flat. Using the orbital sander won’t get the board pancake flat, it doesn’t have enough surface area to flatten. (hate to say it, but using a 3x3x10 inch flat block of wood (Balsa or Agave) and gluing 80 or 50 grit to it will flaten it out real fast), the best is a vari- speed sander polisher. Use the ortibal sander for the light sanding once its flat, use it for the 150 or 220 grit just to get the sanding line out. Anyhow, you have learned the lesson of making the most perfect shape in every stage of the process, smooth shape+smooth glass+smooth hot coat+smooth gloss=less sanding. If you start out with a lumpy shape, guess what you’ll end up with? Ahhhh, nothing like riding a board you can trip over when you walk the nose!


Can I lay a new hotcoat over the current one even though the current coat is sanded over and kind of gummy? Will all that stuff “dissappear”? This might be a lost cause…No worries though, I’m absolutely HOOKED. Thanks for all the help.

Hey tenover, I ran into that very same problem on one of my boards I tried to sand today. The hotcoat had gone off too fast (the blue swirl board in the sun=hot!), so it ended up with the dreaded orange peel effect. It felt slick and smooth, but gummed up sandpaper in a big hurry. I knocked off the surface sheen with a big sanding block and a couple of sheets of 60 grit, then as soon as I got through the surface layer, it loosened up and began sanding normally.

And not a good idea to put on another coat of hotcoat without sanding first. The wax on the surface of the f-ed up one will keep the new coat from bonding. Gotta sand it!!