On Sunday, November 29, 2020 at 10:35:58 AM UTC-8, Roy B. wrote:
Charlie:
The Evercoat comes with its own hardener which I think is PVA based (whatever it is, it smells awful). When I wanted to thin it for spraying I used regular acetone which is also good for cleanup. I found it helpful to lightly sand a larger area than I was going to repair, then mask off the repair area as a smaller section (of what was sanded) that I would use the new gelcoat on. So you went from old gelcoat, to the sanded area, to the newly sprayed area. This allowed the colors to blend a little better than just spraying new gelcoat on the old gelcoat.
ROY
MEKP (methyl ethyl ketone peroxide) is a typical catalyst for polyester resins. Some gelcoats won't harden up on the surface if they're exposed to air.. For finish gelcoats, manufacturers typically put a surfacing compound that rises to the surface and seals the polyester from air. Laminating gelcoats don't have the waxy surfacing compound because they will have additional layers of structural material bonded to them. Those can be made to cure by sealing them with PVA (poly vinyl alcohol). PVA is water based and can rinses off with water or is shed during wet sanding.

MEKP is particularly nasty if it comes in contact with mucus membranes (such as eyes). Take appropriate safety precautions when using it.

Hope everyone has a fruitful repair / refinish season.

Craig
JN