Hi folks, Having problem over tinted resin in hotcoat: 1) An oz white pigment added to 200 ml resin 2) Stir it well for 5 minutes. 3) 3% S.A. added to the resin 4) Still again, 3% cat. added. 5 Stir for another 5 min. The prob is not opaque white enough to cover a balsa made skimboard, especially around the rail where some parts still transparent. Should I add another oz pigment to make it more opaque? It took 10 hours to become tack free, should I add more cat to the resin? Second, just have a another thought, does cabosil add into lam resin to make it sandable? Thanks in advance. Regards, Crabiehk
Lets see- First, that’s quite a lot of pigment, so it slows down the hardening reaction. A little more catalyst wouldn’t hurt. I generally play it this way: addatives ( cabosil, pigment, etc ) or low temps or higher humidity or working in the shade or thin layers need more catalyst, hot days or direct sunlight or thick layers need less - especially really thick filler , like doing large dings. Go real easy on the catalyst with those. I kinda play it as it goes with that and if the resin’s taking too long, maybe set the board in direct strong sunlight. Now, cabosil plus laminating resin just makes real thick laminating resin, you need either the wax addative or sanding resin ( which is, basicly, laminating resin plus styrene wax ). Otherwise, you have a real thick, really gummy resin layer. Try a second hotcoat in the rail area, after lightly sanding what’s there . That’s important, as there will be a thin top film of wax on your sanding/hotcoat that’s there already that won’t do the bond any good, so you have to sand it away. Adding a little cabosil to that second coat will make the stuff thicker so more will stay on the rail and the thicker it is, the more opaque it is. hope that’s of use doc…
Doc summed it up pretty well. I can only add my experience with cabosil in the sanding coat…don’t let it go too hard, like any resin I guess. It does make a tougher, sort of scratch resistant surface though.
do not put silica in lam resin,´cause when you squeegee the cloth, the cabosil will elevate the cloth… in other hand-- add 5% of stryrene wax
My experience with cab-o-sil is it make the resin hard and strong, and hard to sand – have used it to make putty to fill and reinforce joints in other glass projects. Question: Does anyone think adding a certain amount to a “gloss” coat type situation, as mentioned above, would make enough of a difference in the hardness – strength of the coat? Thanks, tO
Don’t go over 2% on your catalyst. 3% catalyst will make a variety of other problems. Use pigment at 2% and if you want easy sandy, use micro ballons not cabosil. Sluggo
?? Why add Cabosil to your hot coats? Just pigment and kick it off, or if your looking fo a black out. Just paint the hot coat and gloss it. I thought Cabosil was basically ding filler?? -Jay
a good hot coat have got silica…always when the finish are sanded hot coat…
hmmm- it seems people are doing different things- do microballons make for a better hotcoat? why or why not?
You can use all or any of cabosil, microballoons, Qcell mixed with your sand coat, no problem. As long as you realise what each of them do. As far as I know Qcell is plastic and microballoons are glass. They will replace resin so make coats lighter and easier to sand, but will never sand glossy smooth and collects dirt easily. It also looks really patchy. Cabosil, coloidal silica, makes the resin thicker and integrally toughens it up. I used a lttle in the laminate and more in the filler and found my boards much more ding and scratch resistant, but a bitch to sand if you leave it too long. None of these have surfacing agents, so for polyester sand coats you must still add wax in styrene. Hope this helps, go get a wave for me.