Clear Gel Coat with Pigment

I have a sabot and I've done quite a bit of repairs on the hull. Some repairs had a dark epoxy material. The original gelcoat color was yellow, so I decided to stick with same color. I'm using a clear gel coat and added yellow pigment (followed mixing instructions/amounts) to get true yellow color. I've added two coats by brushing on, but the darker spots are still showing through - not as much, but they still show. Other color deviations are showing through too. The yellow gel coat liquid appears solid, not opaque, before putting it on. Do I just keep adding coats till the color appears solid? Don't know if I should have put some sort of "primer" on before gel coating the whole thing so that I would have started with uniform color. -dooge

 

I assume your putting yellow on the 'dark' substrate? What is the original substrate colour - white? If so you should have put white in the last resin coat of the repair to help. Best option is strip back and cover with white first. Also check you are sufficiently solid with the pigment 2 -5% is normal allowance, make sure you are at the upper end of this.

FWIW the under(coat) colour matters, yellow is used for gold, grey for black etc and each different material will reflect even the same paint a different colour. So a plastic part the identical part to a metal part will appear different, even if coated at the same time with the same paint.

You'll also find that so called matching colour gelcoat do not always match exactly.... it changes (colour) a bit with hardener, wax etc so tweaking the colour with other pigments is often needed. Getting the right base yellow(s) is important. Don't ask how many 'whites' there are!

 

When I had it all sanded down, it was still "splotchy" because of several previous repair jobs. If I sand the gelcoat off, is there some sort of thin layer of spray (or roll-on) primer that I could put on to make the color even before re-gel coating?

 

There's no direct primer but you can put a thin coat of resin, polyester or epoxy with white pigment mixed in as a 'primer' as you call it. Don't overdo the % of pigment though, and the bond strength will be OK. As yellow is such a delicate colour where the under surface colour is important, try and match the original substrate colour. If it is a real problem, you may need to paint right over it preferably with 2K and a white undercoat so paint is the surface finish.

I have also found that yellow is tricky to match because the % pigment of the original gelcoat needs to be near matched to get similar intensity. This is due to the transparency of the colour (yellow) so test a mix, starting with it on the 'light' ie transparent side. Add a little pigment to intensify until your comfortable with it. Another problem can be the base gel which is 'clear' but in reality has a colour tinge, this can skew the yellow as well.

If you think yellow is bad, you should try matching the transparent gel colours...

You can roll on resin and gelcoat, the latter needs to be quite liquid for it to work well. There are flowcoat versions of gelcoat available.

 

Thanks, guess I'll sand it down and try and put the thin epoxy white coat on, then go on with the yellow gel coat. I don't have to worry about matching the yellow color because I'm painting the whole boat. A sabot isn't all that big.