Since it's raining today and I can't work on the roof, I worked on some indoor projects.
I've been trying to get a good high gloss finish for ages. I think today I finally got the procedure down.
Used the following materials:
5" sanding disks 220, 400, 600, 800, 1000, 1500 Surbuf Random Orbit Buffing Pad, 5-1/2" Meguiars #7 Show Car Glaze Meguiars #9 Swirl Remover ML Campbell Ultrastar Random Orbit SanderMisc supplies--paint brush, lacquer thinner, shop rags, etc.
- Sand overall with 220, and apply a coat of Ulstrastar. Let dry.
- Sand overall with 400 and apply another coat of Ultrastar. Let dry.
- Smooth with 400. Look for spots where the coating is sanded through. When you find one, hit that spot with 220. Apply another coat of Ultrastar and let dry.
- Repeat 2 & 3 until the entire piece is sanded with 400 without penetrating the finish.
- Sand with increasingly fine grits.
- Apply a little bit of Meguiars #9. Polish with the Surbuf and the ROS. Do _not_ try to do this step by hand--it can be done but it will take forever. Wipe clean.
- Apply a little bit of Meguiars #7. Polish by hand or with a second Surbuf.
If there are any dull spots that won't polish, the finish has been penetrated--go back to 4.
The resulting finish is not flat, it's a bit wavy, but it's got a mirror gloss with sharp edged reflections.
I went with Ultrastar because recoating blends the coats giving a continuous film, while the cured properties are very good.
I tried a number of Meguiars products before settling on the two that I mentioned. 3M has equivalents but I don't know which particular 3M items they would be. These are automotive products that you'll find at a good automotive paint supplier. They are not waxes, they are abrasives in a liquid, and are intended for body shop use, polishing between coats of sprayed lacquer--they leave no residue that will impede adhesion of automotive finishes.
There are purpose-made foam pads for use with these materials--you can use one of those if you want to--I don't think it makes any real difference in the outcome.
The objective of the sanding is to get a continuous lacquer film that has been sanded to a degree of fineness that the abrasives in the swirl remover can handle--I found that if I sanded to a courser grit than 1500 the swirl remover couldn't take out the marks but at 1500 it did.
I haven't tried this procedure with shellac yet--I don't see any reason why it wouldn't work, but that doesn't mean that there isn't one.
It should also work with a high build urethane--it just has to build heavily enough in a single coat to avoid sanding through.