For wood, or hard materials such as metal, stone, or glass, the right sandpaper can help tackle myriad projects. Choosing an abrasive suited to the material will save you time in the long run. Consider the type of abrasive, the paper’s weight, and the grit to pick the perfect sandpaper for the job.
The back side of sanding sheets tell you what the abrasive is: garnet (Gar), silicon carbide (SiC), or aluminum oxide (AlO). AlO has replaced garnet in general use because of its longevity and more gradual crystal fracturing. The paper’s weight will be graded from A for light and flexible to F for heavy and stiff. There are also cloth-backed sheets for extra flexibility (for getting into small corners) and durability. The grit will be a number, often followed by an X. Grit is determined by the number of grains per square inch, with 12 the coarsest (to remove paint or to flatten ridges on an old wooden floor) and 2500 the finest (for work on high-gloss finishes).
Garnet’s sharp points are perfect for abrading wood, especially harder end grains. Aluminum oxide’s durability makes it an aggressive abrader, a good choice for wood or smoothing metal. You can sand metal dry, but it’s better to use a waterproof paper, which prevents airborne dust, and the water keeps the paper from clogging with metal bits. Silicon carbide is the hardest of the three, making it best for glass, stone, and marble.
As you sand, start with a coarser grit, and work your way down to a finer one to remove deeper scratches. Skipping a grit makes more work for a finer one, which will take longer. As you advance through the grits, use a linear LED work flashlight to spot anomalous coarser scratches, making sure you don’t miss them before proceeding to a finer grit.
Keep your sandpaper clear of abraded material. If it clogs while you’re sanding, slap the sandpaper face with an open hand if it’s on a block, or hold the paper in one hand, and use the other to flick the paper sharply on the back side with your fingers to dislodge material.
Use a crepe rubber block like an eraser to dislodge clogged material.