Hi guys, I am still learning and I have been using a small mould as a test.  I have just pulled my small money tray made of 2x2 twill carbon out of the mould and there are tiny pinholes on one side of the surface, I am sure that the bag kept full vac all the way through the infusion so my question is what are the main reasons for a pinhole finish. 

I have been working in the garage which is cold but have my mould on an electric blanket to keep it warm.  the only thing different with this infusion is that I didn't use any spray tack on the surface. 

I am quite happy to have these little problems as I want to learn as much as I can but I need to have an understanding of why things happen and how to improve.

Thanks in advance

Nothing good to say......then say nothing

Lots of causes for pinholes, if you can post up a photo then that will make it easier to answer. 

Pics will certainly help, but I've found that working on small moulds with infusion can be tricky, as I think there's a danger of things happening too fast for the part to fully wet out and for any air to fully work it's way from the surface of the mould

Although there're differing opinions on the need to de-gas the resin using a chamber prior to infusion, it can provide a little more certainty of good surface finish, especially where there's not a long infusion process to help take care of things naturally. Of course, if there's any possibility that some of your fabric isn't in close contact with the mould in any areas and is bridging, you're more than likely going to see bubbles, voids or pinholes occurring here where resin is slightly pooled. Careful use of spray tack can be of great help, but be wary of the impact on your surface finish (using a product like GC50 before infusion can help minimise any blemishes if using spray)

I'd also consider sparing use of infusion mesh, so that things are naturally slowed down and allow the resin (pre-warmed if possible) to slowly work it's way to the exit port where some of the air in the flow front can escape before clamping off.

The parts you'll see in the attached link are very small covers that were probably a bit small,  in a practical sense, for infusion and I would likely do them in pre-preg if I did any more, but following some of the elements mentioned above they came out with a perfect finish

https://www.dropbox.com/s/sxoxp15vhbkch35/20160113_180336.jpg?dl=0

Thanks guys, its a bit hard to see from the picture as I found it very hard get a good picture of the tiny pinholes on the surface.  I think that the infusion probably went a bit too fast as when I opened the inlet line the pipe was sucked closed and when I squeezed the kink the resin rapidly shot in but seemed like it had good coverage.  I think I will try again this time going really slowly. 

Also I  will be looking into making my own de gassing pot.

Nothing good to say......then say nothing

A little hard to tell from your pic, but the surface finish does look a little resin starved (unless your mould surface is not that glossy?).

Yeh I'd say it's a little bit dry for a cosmetic surface. You'll get away with that when everything else is done perfectly, but if you've got some air bubbles in your resin pot from mixing the resin and you infuse a touch too fast then all these little things add up to give you issues like this.