It’s rare that I tout a product as being wonderful, especially when it has wonder in it’s name, but get this Loehle wonder-fil. The pint size can will last you forever. Basically you wipe in on. I usually just put a dab on my finger and rub it into the pinholes. Then you wait a 10 minutes or so and wipe it off. Then paint.
I don’t like the paint over them option. The paint doesn’t always soak in to the hole. It just bridges it. Then the hole reappears when you sand the clear. Or it reappears months later for no reason at all.
I think it is difference in the types of products we produce, 80% of my moulds are larger than 5’x5’ - when demoulding the part will flex, we use or have used for in mould coating PPG clear, Epifanes clear varnish, Duratec & a host of others. Some work well, just about all clears (quality) ones at least have (flex agents) etc…Don’t get me wrong, I didn’t mean every time it has cracked, just that it has happened.
We made two test parts and they were perfect. If you go very very close you can see the pinholes if you know where they have been, but the result was fine.
I applied it like a filler, let it dry and then light sand it with a scotch brite and clear coated, even after clear you could see the print of the pinhole, and the second thing i didn’t like was that a black dot could be seen between the intersections.
I used shoe polish once. I had to spray paint a carbon boat white. I warned him that pinholes might show up. Finally there was a 5x5cm area which had pinholes. The customer went beserk, and demanded a respray. I filled the holes with shoe polish, the customer never noticed.
It looks white in the can but it disappears when painted even with clear. Kind of like how a super light fiberglass disappears when you infuse it over carbon. After all you’re just putting a tiny spec in a little hole
I stopped playing that game with pin holes and clear coat. I gel coat every mold before we make a part, lay up, infuse, pull, trim, sand, clear once, and done.
I bought the marine gel coat you suggested but have not tried it since I started using MTI hose. I haven’t had any pinhole issues until this last part. It was a large part so maybe I didn’t degas long enough or infused too quickly… I’m not sure. I was going to try and fill the pinholes but when I started really looking the entire part was cover in holes so I scrapped it and will have to try again.
I use it regularly and like it. If you know what you are looking for, you will see little black dots at bundle intersections but only if you are specifically looking for them.
@Dominik: where do you get the clear filler? R&G only has black as far as I can tell.
Herman I found a post where you suggest vinylester for overlays,
Thread: Best Epoxy resins for overlay - “For overlays I like vinylester, for its high Tg at RT cure, and less prone to yellowing than epoxy. Also, there are special (polyester) gelcoats that are less prone to yellowing, specifically for carbon work. (Nord Composites)” Wouldn’t this also suitable for filling pinholes? The only problem I guess will be it’s brown color which may make the carbon wave look a bit of yellow?
