Dear all,

Ok, making progress ! I am going to do some pre-preg in the near future, but not quite tomorrow, because the build up of my oven is delayed due to the lockdown...

Now question about the finish...I am pretty OK with making molds of relatively complicated parts. I use hand layup then vacuum bagging, and all this works pretty smoothly. THe parts I build are quite OK, but the finish is not so very good. I always have some small bubbles or so that force me to brush another layer of epoxy at the top, then sand, then brush epoxy again...this is what takes most of my time when making parts, and it is pretty frustrating. I know that one can reach perfect finish right out of the mold, but I cannot work in the conditions to do so. I am just doing stuffs for myself, in my garage...so nothing really optimal and I think I have to live with not prefect out-of-the-mold finish. Now when I apply some epoxy coat on the parts, it is also incredibly frustrating, because with the brush, even at good temperature, it's never really flat. And also it is thicker at the edges, making the subsequent sanding a real pain. Any advice ? I was considering using an airbrush to spray very thin layers of car varnish (I am only doing small parts, so the airbrush is good enough). Or is it a bad idea ? I see people using an epoxy gelcoat in the mould for make the very good surface...but I tried something like that and with the release agent, I don't manage to get that gelcoat smooth on the surface, it makes massive fish eyes all over the place... Anyway, if someone has a relatively simple solution for me to make part finish easier, that would be soooooo helpful, because I am getting really fed up of spending so much time sanding/brushing/sanding etc...all this to get something that is not perfect either.

Finally, a need to make parts that are smooth on both sides. So I was thinking of using a mould / counter-mould approach. But how does one make sure that there is no big air bubble trapped between the carbon and the counter-mould ?

Thank  you !

Small Bubbels or pin holes could be from couple of diffrent reasons. 

1- Bad mixture
2- High or low room temperature
3- Too much resin flow in surface
4- Wrong resin
5- Low pressure 

If you could share the picture your pin holes or bubbles and also list of your composite materials. I think i can give more detailed information.