Building Cabinets 6 - Sanding and Finishing
Before you attach the doors and false front to the carcass, you should sand and finish them as well as the carcass. Then install them onto the carcass.
Sandpaper is graded as medium, or numbers 60, 80, and 100. Fine sandpaper numbers are 150, 180, and very fine 220, 240, and 280. Medium is usually used for the first sanding, fine for smoother results and very fine for smoothing finishes between coats. Sandpaper can be used wet for some finishes.
You can fill in nail holes with wood putty/dough before sanding if you are not planning to stain the wood. If you are staining, fill the holes AFTER the stain is applied. In either case, match the wood puffy closely in color to the stock or use saw dust and wood glue to make your own puffy.
- Sand with a fine, wet sandpaper (start with a 120 grit on plywood and 60-80 grit on other lumber) wrapped around a felt pad or use a pad or orbital sander. Use aluminum oxide sandpaper because its grit material lasts longer.
- Sand slowly so you don't go through the veneer. Vacuum frequently to remove dust. Finish manufacturers recommend which grit of sandpaper to use with their specific finishes to achieve the smoothest result. Feel the wood to check on the smoothness as you work because touch is really the only way to get a smooth surface. Make sure that you remove all dust, finger- marks and excess glue before applying the finish . First vacuum or brush the entire piece clean and then wipe with a tack cloth.
- An optional step here would be to use a sanding sealer, which seals the wood so the stain goes on even.
When it is time to polyurethane, vacuum the room and let the remaining dust settle for 24 hours. Wear lint free clothes and use the fastest drying polyurethane available. Use a tack rag to remove dust before applying polyurethane and between coats, after you sand. Do not apply polyurethane over a coat of shellac or lacquer. A polyurethane finish is recommended as it is highly water resistant and cabinets usually have a lot of water splashed on them.
The finish can be applied with either a brush or an air compressor and spray gun.
If you are using a nylon brush, follow these suggestions.
- Position the piece in horizontal sections.
- Apply the paint, varnish or stain across the grain.
- Brush out the paint with the grain, using the brush as a wiping tool. Clean the brush as it collects liquid.
- Pull the brush across the unit's surface with the bristles held almost vertically.
- Let each side dry between coats.
Check the varnish to see if a certain stain is called for. Read the label for drying times and how many coats to apply. Apply two, preferably three coats of urethane varnish using a good quality natural bristle brush. Between coats wet sand the finish. Rub the surface till it feels smooth. Wipe off any residue and then apply the next coat. To get the best finish, rub with fine pumice or mineral oil.
You can use an air compressor with a paint attachment to apply many finishes. it saves time, avoids brush strokes and applies a smooth finish by delivering a smooth coat. It is especially good to use on a lacquer finish as it dries very rapidly and brushing can be difficult. Hold nozzle 6" to 10" away from surface. Keep it at a right angle and straight up and down, not tilted. Move your arm back and forth parallel to the surface. Pattern should "feather," overlapping without sharp edges. Pull trigger after stroke begins and release before it ends. Stop on to two inches before corners and sweep around corners, hitting both sides in the same sweep. You may want to consider a spray booth to avoid dust and the mist.
Apply your finish in a well ventilated space with lots of room. Cover the floor in the area that you will applying the finish so that if a spill occurs it will not leave a permanent stain. Follow the manufacturer's instructions.
The finish is the first thing you and your friends will notice, so take your time!