Sanding is often the most overlooked surface preparation step with bare wood as people generally think “bare” means ready-to-go. Yet, the quality and uniformity of finished piece is dependent on proper sanding. For best results, follow the simple steps below.
Selecting the right abrasive and/or tool for the job at hand
When it comes time to tackle a home project that involves wood sanding, first consider the size of the piece when determining project needs. For smaller, harder-to-reach and more intricate areas like furniture or molding, you’ll likely want to use sandpaper sheets or sponges that offer the versatility and mobility to reach tighter areas when removing paint and finish for the next step. For larger jobs and flatter surfaces, electricpowered sanders are the best, quickest, and easiest way to sand wood. With all the sander types on the market, how do you know which to choose?
For every sanding project, there’s a complementary abrasive:
Selecting the right grit sandpaper
Whether you choose to use a power sander or sand by hand, you will want to make sure to begin your project by using the finest grit of sandpaper to start that allows you to get the job done effectively. For heavy sanding and stripping, you need coarse sandpaper measuring 40 to 60 grit; for smoothing surfaces and removing small imperfections, choose 80 to 120 grit sandpaper. For finishing surfaces smoothly, use extra fine sandpaper with 360 to 400grit.
Keep in mind that the goal when sanding is to take away material from the surface to remove imperfections and/or shape edges, so you’ll want to start with a sandpaper grit that is just coarse enough to remove these imperfections without gouging into the material further; typically this is an 80 grit for planed or shaped wood and a 100 grit if the wood does not contain blemishes. Since both 80 grit and 100 grit paper leave minor scratches, the next step is to sand with a finer grit paper and replace these scratches with less noticeable ones. As a general rule, if you started with 80-grit paper, skip to 120 grit paper, or if 100 then to 150. Finally, sand with 220 grit sandpaper.
Note that it is essential to know the type of wood you are finishing before starting to sand as this has a direct relationship to the grit used for final sanding. There are two basic types of wood, softwoods and hardwoods. Understanding the difference can help prevent you from over sanding and creating a situation where the wood piece will not accept finish. With typical softwoods like pine and alder, start with 120 grit abrasive and finish with no finer than a 220 grit for water based stains and 180 grit for oil based stains. For hardwoods such as maple and oak, start with a 120 grit abrasive and finish sand no finer than 180 grit for water based stains and 150 grit for oil-based stains.
Some of the wood dust from sanding may become airborne; so, it's wise to wear a dust mask, gloves and safety glasses while working.
Prepare your workpiece for sanding
Scrape off any glue residue from the assembly steps and sand uniformly to remove any traces. Glue residue limits the ability of the stain to penetrate the wood surface. Clean all surfaces with a microfiber cloth to remove wood dust.
Sand your workpiece
When using a power sander, always sand parallel with the wood grain to avoid scratches. Keep moving the sander at all times so you don't leave any unwanted indentations. Always start with a coarse grit belt or disc and work your way progressively through finer and finer grits until you reach the desired level of smoothness. Don't press down too hard or you'll clog up the abrasive disc or belt; let the weight of the tool provide the right amount of pressure.
Should you choose to hand sand, you’ll want to follow the same general process of starting with coarse grit sandpaper or sponge (80 grit is a good place to start) and moving through the grit range until you reach the desired level of smoothness. It is best to sand with the grain of the wood, especially during the finishing stages.
Clean and prepare for next steps
Once done sanding, clean all surfaces with a microfiber or tack cloth before applying stain, finish or paint.
Sanding between coats of finish
Once finish or paint is applied, your workpiece will need to be sanded again to smooth any surface imperfections or debris in the finish for an ultra-smooth result. For sanding the first coat of finish or paint, which is considered the sealer coat, sand with 180 to 220 grit sandpaper for oil-based and water based finishes and 220 grit for paint. After applying the next coat of finish and allowing it to dry, follow up with 220 grit for oil-based finishes and 320 grit for water based finishes and paint. An optional step for painted surfaces is to sand before the final coat with 400 grit, especially if a high-gloss sheen is being used.