Hotcoated the bottom of my board this past Friday. Borrowed a nice Milwuakee snader from a friend and when I when I went to use it to sand my hotcoat, it completely just gummed up the paper right away. I had it on the lowest RPM’s with 80 grit. I then took out a block with 80 on it, and sure enough, after 10 seconds, the paper was completely gummed up as well…Any ideas? I used pre-mixed hotcoat that I bought from Mitch’s. It just seems like if I keep trying to sand it, I’m going to go through $4000 worth of sandpaper. The deck sandded down just fine.
Sounds like either it hasn’t gone off completely or else you got some with a helluva lot of wax in it.
Either way, try putting the board out in the sun for a while to maybe speed up the cure, harden it some. If it’s slippery to the touch after a little time out there, then it’s excess wax, which a paper towel can get the worst of.
Also, if you happen to be going by a tool store, woodworker’s supply or something, you can maybe pick up one of the sanding belt cleaners…looks like the biggest gum rubber eraser you ever saw… and that can sometimes get the worst gunk out of the paper/discs, like it does with sanding belts.
I’ll go home at lunch and stick it outside for awhile…The hotcoat was done in temps in the 80’s, how long do you normally let your hotcoat cure before you start sanding it? I was under the impression that you could sand within a couple hours…
Oh, lots of variables, man. Sunlight, humidity, how good your catalyst was or wasn’t, any residual smeg on the surface you’re hotcoating. Lee has the right of it, if it hasn’t cured in a couple of days ( though less if it’s over a darker color- beware of baking boards ) then it’s recoat time.
I’d also note, from sad experience, never leave your catalyst in the sun or any real heat. Breaks it down very quickly. Best to keep it in the shop refrigerator, maybe in a vodka bottle so it’ll not only stay pretty good, it’ll discourage those who would heist your booze. Or, if you don’t feel like living dangerously ( or like me you don’t trust your memory any more) , a dark-colored bottle is good, as used for various medicines that are also UV and light sensitive. If you’re doing lots of dings, the type of bottle with the dropper in the cap is especially good.
If you buy premixed hotcoat resin in a gallon can the wax will settle to the bottom.Depending on how old the batch is you can sometimes shake it up or you may have to insert a stick to loosen it up.Sounds to me like the wax didn’t rise.Its best to mix your own.Surfacing agent (wax sol) is dirt cheap.
Since I’ve “kind of” sanded the entire bottom (No real big shinies), can I hotcoat over that? I’m thinking if there’s no wax, it should stick, and if there was wax, it should pretty much be sanded off now.
Providing that the resin is fine… there just wasn’t enough wax, to block off the air, to allow the resin to harden. All you need to do is get it to harden and you’re golden. So a super thin layer of hotcoat or gloss would do the job. You’re going to sand through this layer anyway, so even if it doesn’t stick to your first layer that’s OK, so long as it blocks air (might even be better).
I’ve been thinking that acrylic should suffice in this situation… it’s air tight, thin, cheap, and easy to spray. Plus it’s easy to sand off. I’ve never done this, and have been too lazy to try a test of it. But worst comes to worst there is an extra layer of acrylic in your composite.
I had the same thing happen to me a couple of boards ago. Asked the same question as you. I kept sanding the bottom and tossing the paper. After a while the hotcoat sanded as usual. It seemed the gummy stuff was on the very surface. Normal stuff underneath. For what its worth. I’m looking forward to hearing how those boards ride. Still the fishes? Mike
Yup- That’s what happened. We sanded the crap out of them last night, and probably wnt through 3 or 4 sheets of gummed up 60 grit before, like out of nowhere, BAM! They started sanding like they should. Very odd. Once they started sanding properly, it was great, but before that, I’d rather have gotten in a car accident…Not fun. and we noticed that the rails sanded very easily right off the bat, but the “flat” surfaces took about an hour of sanding to get them to go down like normal…