Coating Vacuum Form Bucks

I'm Having a problem with the paint I used on my vac bucks bubbling and peaing just proir to forming. I use a vertical oven so the heat is blasing down through the plastic onto the buck. This has caused damage to the bucks. every time I form I have to sand the bubbles down smooth.
What are most of you using to prevent this. I know the clam shell guys shouldnt have this problem.
The bucks are made from Pine and MDF with spot filler and bondo under the primer. I used sandable primer.
Maybe some high temp paint would work but I would like to hear from some of you

Greg

Im just starting to learn this process of buck making from MDF, but is it really necessary to paint the buck after priming it?

-tubachris

I don't know, But the primer is what bubbling on mine. Maybe my oven is just to close to the buck. I just lowerd it about 5 inches. It also has a forming heat so you can keep the heat on when the sheet is beeing pulled. i kept that on this time. That might be the prob. I was just wondering if anyone had any simelar problems
Greg

Im sure that if you raise your oven up a bit higher that it will stop having this issue. I dont think also that you really need to have the oven that close either to have good pulls.


-tubachris

I use an aluminum cookie sheet as a heat shield. It reflects IR back up to the plastic. That has the nice side-benefit of giving you double-sided heating.

What kind of primer do you use, that's peeling?

By the way, professionals often make bucks out of epoxy with various fillers and/or finish them with epoxy. Epoxies are generally pretty heat-tolerant. (And some epoxies are very heat tolerant.)

You can make a bondo-like sandable putty with epoxy resin and glass or phenolic microballoon filler, but I don't know where to get pre-mixed stuff like bondo. (Bondo is just polyester resin with microballoons, IIRC.)

I know of several guys who coat their bucks with outdoor grill paint. Its made for high heat resistance and sands well. Just something to think about.