Wet sanding are a process in which sandpaper and water is used to smooth a surface. Wet sanding is a process that remove imperfection from surfaces like automotive paint, metal, or wood. Wet sandpaper is more different than dry sandpaper in that wet sandpaper contain silicon carbide grains that are fused to a waterproof backing.
This waterproof backing allow the sandpaper to remain functional while the user applies water to the surface. Water is used in the sanding process for a specific purpose: to flush the removed material away from the sandpaper. This flushing of the material from the wet sandpaper prevent the sandpaper from clogging.
Wet Sanding: What It Is and How to Do It
If dry sandpaper is used on painted or metal surfaces the sandpaper will quickly clog. Wet sandpaper will continue to sand the surface cleanly due to the properties of water that removes the sanding debris. The term “grit” refer to the size of the abrasive particles of wet sandpaper.
The grit size of the sandpaper determine the amount of material that the sandpaper will remove. Coarse grit sandpaper contain large abrasive particles and is used to remove heavy material from the surface. The coarse grit sandpaper will leave scratches on the surface that using sandpaper of the next grit size will remove.
Medium grit sandpaper contains smaller abrasive particles than coarse grit sandpaper and is used to smooth the scratches left behind by the coarse grit sandpaper. Fine grit sandpaper contain smaller abrasive particles than medium grit sandpaper and is used to remove the marks made by the medium grit sandpaper. Using medium and fine grit sandpaper to remove heavy material will cause the sandpaper to leave deep scratches on the paint that will be difficult to remove.
Wet sanding require the use of a specific sequence of grit sizes. The grit size that you should use is one that match the damage that exists on the automotive paint. Use soapy water as a lubricant for the sandpaper.
Use a squeegee to wipe the surface of the automotive paint. Use low-angle light to ensure that the wet sanding surface is level. After one grit size has been used, you should use the next grit size to further refine the paint.
When using finer grit sizes use a lighter touch on the paint. Skipping grit sizes will waste the sanding process and may cause imperfection in the sanding process. Some of the lubricants that can be used for wet sanding are plain water.
Plain water can be used to rinse the debris from the wet sandpaper. Add dish soap to the water used for wet sanding. Dish soap will reduce the friction between the paint and the wet sandpaper and the debris will remain suspend in the water.
Mineral oil or light sprays can be used for sanding metal or fine automotive paint. The use of mineral oil will extend the life of the wet sandpaper and create tighter scratch pattern on the painted surface. Using the wrong lubricant will leave residue on the sanded surface or may cause corrosion of metal paints.
Wet sanding is used on wooden surfaces but with care because water may raise the grain of the wood. Wet sandpaper should be used between coats of finish on wooden surfaces. The reason for using wet sandpaper on wooden surfaces is that it will flatten the fuzzy texture of the raised grain of the wood which allow the finish to bond to the wood properly.
Depending on the material to be sanded, different approaches to wet sanding may be used. Use coarse wet sandpaper to remove marks on aluminum and use medium grit sandpaper to sand stainless steel to create a directional grain. Chrome should be sanded with fine wet sandpaper with oil-based lubricant.
Metals that are soft like brass require the sander to use very light pressure when sanding. Plastics and acrylic require the use of water when sanding the materials because water will cool the plastic and prevent it from melting due to the heat created by the friction between the sandpaper and the plastic. The technique that is used when performing wet sanding will have an impact on the outcome of the sanding.
Use foam blocks when sanding curved surface because the foam will flex. Use hard rubber blocks when sanding flat metal panels because the rubber will remain flat. Use a cross-hatch sanding pattern when wet sanding.
Change the angle of the sandpaper when sanding to remove the previous scratch pattern made by the sandpaper. Tape the edges of the painted surface before beginning to sand the paint to prevent sanding through the paint to the primer. The use of water is essential in the sanding process.
If the sander dries out the paint, the wet sandpaper will clog and create random scratch on the painted surface.
