Hello,
I have a question about a problem I am having. I know that it is not advised to use spray adhesive when you want to create visible carbon parts with infusion BUT, I am in the process of creating quite intricate airbox design which consists of 3 main parts one some small bits and pieces, but the main shape is the most complicated one, it is 2times split mould, one I manage to infuse in one go, the second shape needed to be infused separately and then joined together in mould.

My question is, i have quite a bad surface finish and I would say it is most likely due to using spray adhesive, but in my opinion it is not possible not to use one becuase of the compliacated shape the mould/part has. It also leaves residue in the mould after releasing and it can be cleaned off with acetone, but then i am worried that it will also wipe away separator (i am using Semiperm™ Monofilm)

For spray adhesion I use INFUTAC clear - which states it is suitable for visible carbon parts...

The proces of what I had to do now was to clear it with layers of resin and sand it down and after that apply final matte clear.

Below are pictures of parts out of mould.
What would be your advice? I want to try spraying the adhesive on the fabric instead of mould, but i dont know if that will help something.

Use an in-mould coating, this will hide the effects of your spray adhesive. Downside is if you get any pinholes or voids, they will be virtually impossible to fix.

I am fairly certain that in the first picture the surface finish is not only due to the spry tack.

However, instead of workign with a in mould coating as proposed before, i would personally change the spray tack. For those applications i had good luck with the isotacker from sicomin. It doesn't work as well as the aerofix 2 which we usually use, but when basically used as a contact glue with a thin mist on fabric and mould it is reliable enough and leaves no visible trace if you don't overdo it.

cheers, Lester

Thanks everybody for the input. I was doing some testing and some parts made.

I tried in mould clear gelcoat. What did went wrong was that i had a lot of pinholes in between the gelcoat and fibers...

What i tried then was to not spray the adhesive on mould but only just on cloth. This definitely improved the surface finish by a lot. But i am still not satisfied (damn perfectionism). I still get some pinholes in some areas. Which can be cleared off with resin and sanded, but i still would like to be able to create good finish without pinholes. For example like in this  Video, when he takes the big part out of the mould it looks like it is completely pinholes free. And he uses in mould spray adhesive.... i might try different brands which may help.

What i discovered that parts on where i had more infusion mesh, there were less pinholes, and on parts where mesh wasn't throughout the whole part, there were visibly more pinholes, where the resin traveled only through fibers. Should this solve the pinholes problem? but i am worried using mesh on some sections because there is a lot of small edges and i am afraid that there is bigger chance to have gaps or bubbles trapped underneath.

Thank you for posting this! I had the same question! (Spray glue to hold cloth down/PVA) Fortunately, this part I am working on is a below the hood part nobody will see.

I have had a tricky time settling on finish/gel coat on my main hull The body/neck of a small viola/cello/guitar size instrument I make. I was intending on going to an in mold gel coat but want to avoid polystyrene types and the thixotropic epoxies were hard to apply in terms of uniform thickness. (Plus, they were a bit too tenacious sticking to the mold (even with ample PVA etc.). I have been experimenting with food grade epoxy finishes but do find them tricky with contaminants/fish eyes etc. Besides Acetone, any good pointers on surface prep?