There are a lot of different steps and techniques involved with wet sanding paint, but before it even begins, it is equally as important to pick the right sanding block to start out with. The first step is the most important, it’s when the clear needs to be cut completely flat, getting rid of all the orange peel and any ripples that are in the paint. The right sanding block, along with 600 grit, is how it happens.
I’ve found the best route is using acrylic blocks. The key is for the block to be solid and dense, as acrylic or ‘plexiglass’ is. This doesn’t mean the block can’t be flexible. You want the block to follow the contour of the panel, with just a little bit of tension. Too flexible, the ends of the block will want to dig in, and too rigid, the center of the block will be the only part of it sanding, also leaving grooves in the panel.
Most panels that are really flat and really straight, the 1/4″ thick piece of acrylic can be used, it really doesn’t bend at all, and will cut the clear super flat. For any areas that have a slight curve, or if there is even a tiny low spot, the 1/8″ thick piece works perfectly. You want the block you choose to follow the body work, which will in turn cut the flutter and ripple out of the paint. Don’t just think that because it’s a thick solid piece of acrylic it will work the best, it probably won’t. I would guess 85% of the time I find myself using the thinner piece (1/8″).
As for curves, the same rule applies. For something that is really straight with little shape to it, the best option is the plastics tube that won’t bend. A lot of times I still use the 1/8″ acrylic through these areas (another blog post to come). Last resort is the round durablock, but beware, durablocks struggle to get the clear flat enough.
Very rarely will you ever need any other size or shape sanding block. Don’t over think it, and pay very close attention to how the sandpaper is cutting.
The blocks are just under 5 1/2″ long, and about 1 3/4″ wide. The thicker acrylic is 1/4″ thick, and the thinner piece is 1/8″ thick. Most hardware stores like Lowes or Home Depot carry smaller sheets of acrylic, and McMaster-Carr has a great selection. Just buy a sheet and cut your blocks out of it.