Getting an ultra-smooth, glassy finish on wood using a film-building finish like polyurethane requires leveling the surface between each coat. When I say level, I don’t mean dead flat. I mean that after sanding, the entire surface has the same sheen or lack thereof.
To accomplish this, you need a sanding block that’s firm, with just a little give. A sanding block with no give — like a typical rubber sanding block — doesn’t work well for this purpose. A hard felt block is the holy grail, but a sandpaper sponge works pretty well, and they’re readily available. My frustration with sanding sponges, however, has to do with how quickly they wear out. So I started reusing them. I just use them like any other sanding block by wrapping them with whatever grit sandpaper I need. I haven’t had to purchase a new sandpaper sponge in years.
— Brad Holden, Associate Editor