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 sanding sponges work 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 one in years.
— Brad Holden, Associate Editor