You may have a nice piece of trim or baseboard you need to sand in preparation for painting. Choose a too-coarse sandpaper grit, and you can end up gouging non-repairable grooves in your expensive trim. Choose a grit that is too fine and you may end up sanding from now until infinity and get nothing accomplished.
Welcome to the world of sandpaper grit.
Grit Gauges: Backwards and Often Confusing
- Numbers Are On the Back: Grit is expressed in the form of numbers on the back of the paper. These numbers range from 24 all the way up to 1,000, though in practice most homeowners will never use grits at the top or bottom of the scale.
- What Grit Numbers Mean: Grit does not mean the number of grains deposited on a square inch of paper. Rather, it refers to the number of holes per square inch in the screen when sieving abrasive grains.
- Backward Numbers: Grit sizing is counter-intuitive. The bigger the number, the smoother the paper. The lower the number, the coarser the paper. So, the best way to look at this is simply to remember that the numbering runs backward.
Why Are They Different?
Simple: coarser paper removes the unwanted material faster and with less effort. Yet coarse sandpaper from #50 on downward can easily damage your project--all in the name of speed.
It is wishful thinking to plan on sanding out your gauges by stepping down to finer and finer grades of sandpaper. You are just creating more work for yourself. So, the best thing to do is pick a sandpaper grit that is appropriate for the job.
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Normal Grit Ranges
While you can find scores of differently graded sandpaper available, you will probably only use a small handful:
- #50-#30: Very Coarse Grit - Rips off peeling paint and extraneous materials with ease. Also, risks damaging your project. Not recommended for fine pieces such as trim or furniture.
- #80-#60: Medium Grit - Your universal grades of sandpaper. It is hard to go wrong with sandpaper grits in this range. You can work down difficult materials by applying more pressure to your workpiece. Or, you can preserve fine materials by letting up on the pressure.
- #180-#100: Fine - You would never use these grades of sandpaper on the first run-though. Grits in this range are always for second or third sandings. Sometimes, fine grit sandpaper is used to "roughen" down glossy paint in preparation for applying another coat of paint.