Some of you may have followed my other post Intake/inlet project from a few months back.  I've made a couple more of these pieces, from plugs, and am still very disappointed with the cosmesis.   It looks decent from 3 feet away, but if you carefully inspect, the flaws are evident.



After the final layer of carbon fiber, I'm putting down about 4-5 coats of resin (Marine 820 system).  On my initial piece, I had no clue about degassing - so I was just mixing it and painting it on.  But for this piece, I've degassed in a proper vacuum chamber for about 7 minutes and the difference is obvious now - zero bubbles.  I'm using cheap "chip brushes" to gently coat the piece (disposing after use).  

After those 4-5 layers I have a fairly glossy and nice looking top coat, albeit very uneven as I don't have any system to rotate the piece while it dries for even resin distribution.  There aren't any visible defects/imperfections at this point, just the very uneven surface.


So then it's on to wet sanding.  I'm using a Porter Cable random orbital (thankfully not by hand!!) with a 3" pad and 3" discs, starting at 400 progressing to 1500 grit.  Here's what I'm left with after an hour of wet sanding.  It actually seems to look worse the 'deeper' and longer I go wet sanding. 


The smaller, pinhead sized dots seem to vanish for the most part when the piece is wet - as I do notice that when coating with another layer of resin (or wetting the piece) - a LOT of these imperfections vanish.  But it just seems like there's room for improvement with my process.  Anyone with thoughts on where to improve?  Thanks much.

Yes they are air bubbles. 

You will probably find this has a lot to do with your resin. Expulsion of air is a property of the resin, and some systems just don't do it very well. Which then means you need to put on very thin coats so that the air doesn't have to move very far to the surface, and use of a heat gun will help as well. Then I will also normally get to the stage you have, clean the part very well with compressed air then soap and water, then a prep solvent, and then apply one final layer of resin very very thin. Not looking to build any more thickness, just looking to almost wipe resin into those pinholes. Allow to cure, then a quick knock back with 1200, then spray a 2k clear coat.

In general, I think air inclusion is just part of the process. You can get pretty good results, but I dont know if I have ever got a perfect result with absolutely no air. So you may need to adjust your expectations as well. Not to say you can't improve you've got there, but just don't beat yourself up over a handful of pinholes if you do come across them.