So, I cut a corner and had someone do some finishing on my mould because I was pushed for time. It was a mistake – the mould had a lot of resin dripped on it, and the surface gel-coat was very orange-peely.
It was a perfectly servicable mould, but the transmission tunnel is something everyone will see when they look into the car, so I want it to be facing quality.
In order to sort the mould, I tried 600 grit on a sanding block, and it was making an impact, but not flatting it out as fast as I wanted (i.e. in one lifetime). Then I remembered that I had bought some 400 grit disks from East Coast Fibreglass’s clearance page. Add the disk to the heavy duty polisher I have, and off we go. They really chew through the gel-coat. I finished that with a 1000 disk and polish. After polishing, I saw that I had some fine scratches, so I flatted it by hand (600 and then 122 grit), and polished it back. Again, some scratches. I don’t know if they were being introduced by the polishing sponge, but I don’t have the will to keep trying.
What I have got is a mirror finish on the surface now, with some minor scratches which you can just see at the bottom. I’m hoping that a few layers of release wax will help fill the scratches, and I’m going to use a clear gel-coat before I infuse, which will then end up with some slight positives where the scratches are. These will be easy to flat and polish by hand.
I don’t want to flat back again in case I end up going through the black gel-coat.
I’m not sure if I’ve contaminated my polishing sponge or not here – more experimentation is required I think.