Wet sandpaper provides the smoothest finish of all sandpaper products. A mainstay of auto-body shops, it's also used for wood finishing when only the glassiest finish will do.
Wet or Dry
Sandpaper categorized as wet can also be used dry. Water or a water-detergent mixture reduces scratches by lubricating the surface. Water washes away loose abrasive grit, and in the process, prevents sandpaper from loading up with gunk and becoming ineffective.
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Part of a Process
The use of wet sandpaper is part of a process in which sanding is done between each coat of polyurethane, varnish, lacquer or other top coat, with a progressively finer grit to remove surface imperfections.
Starting From Scratch
Step 1: Apply The Top Coat
Apply a finish of your choice to wood. High-gloss products sand to a brighter, glassier finish than semi-gloss or satin. Allow the product to dry according to label directions, or overnight.
Step 2: Mix With Soap
Pour about a 1/2-inch of water into a small tray. Add two drops of liquid dish soap and stir lightly.
Step 3: Sand with 500-Grit
Attach a strip of 500-grit wet sandpaper to a hand-sanding block. Hard rubber sanding blocks work best. Dip the block into the soap and water solution. Sand the wood lightly with a circular motion. Continue dipping the block into the water to keep the surface of the wood wet.
Step 4: Dry and Examine
Periodically wipe the surface of the wood dry to inspect it. When the surface has a uniform, consistently dull appearance, wipe it off and allow it to dry.
Step 5: Second Coat of Finish
Apply a second coat of your chosen finish, and allow it to dry overnight, then sand and wipe it again. Apply a third coat of finish and allow it to dry for at least 48 hours. It's essential that it's dry.
Step 6: Sand with Lighter Grits
Attach 1000-grit sandpaper to the sanding block. Repeat sanding as in Steps 3 and 4. When the surface is consistently dull, attach 1500-grit and repeat sanding and dipping. Finish by wet sanding it with 2000-grit sandpaper. Buff it dry with a soft cloth.
Step 7: Polish if Desired
Polish it to a bright sheen with woodworkers paste wax or an automotive wax if desired.