A high-quality finish starts before you ever open a can of stain or varnish. I’ve found that the simple surface preparation steps leading up to finishing can often make or break the end result. It’s tempting to rush the process, but a little patience up front can make the finishing go easier and turn out better.
The goal is easy to define. You want to end up with a smooth, clean, consistent surface on which to apply a finish. To achieve this, I go through a systematic, four-step surface prep routine.
First, I search for and remove any glue spots or squeezeout. Next, I take care of any surface blemishes that might be noticeable once the finish is applied. Third, I give the entire project a final, pre-finish sanding. Finally, I clean the surface to remove sanding dust and any other debris that might interfere with a smooth finish.
1
NO GLUE.
Glue spots and squeeze-
out are the bane of finishing.
Glue on the surface blocks penetration of a stain or finish and creates an unsightly off-color blotch.
The best cure for glue blotches is prevention, of course. But this isn’t always foolproof. To be absolutely certain there’s no glue left on the surface, you need to perform a final “inspection and removal.”
Start with a thorough examination of the most likely places — at or near the joints. Large beads of squeezeout are easy to find, but thin smears are harder to see. One way to make them stand out is to wipe the surface with mineral spirits (lower right photo).
Once I find glue, I go about removing it in a couple of different ways depending on the location. On flat surfaces, you can scrape or sand it off. If the glue is in the corner, I start by carefully paring away as much as possible with a chisel. Then I use a damp rag to soften and scrub away the rest. (Ordinary PVA glue can be removed with water and a little elbow grease.)
2 FIXING BLEMISHES. Visible dents, dings, or minor chips are almost inevitable. Sometimes a blemish is simply a small defect in the wood that you weren’t able to work around.
Depending on the type of blemish, I approach it with one of two fixes. Shallow dents can usually be lifted with steam, as shown in the box on the opposite page. The steam causes the wood fibers to swell, leveling the depression.
If wood is missing or the surface has a natural defect, you’ll have to repair it with filler. There are a lot of different formulations of wood filler. The two most practical for filling minor dings are the pre-mixed water-based and solvent-based types. Both come in a variety of colors and dry quickly to a hard surface that can be sanded. They’ll also accept stain to a degree.
I generally choose a color that’s a shade darker than the wood in the project. The filler tends to dry lighter than what you see in the can. The flat tip of a screwdriver makes a precise applicator. Try to limit the amount of filler you spread to the surrounding area. It can fill the pores of the wood and show up once the finish is applied. When the filler is thoroughly dry (check it with a fingernail), you can easily sand it flush with the surface.
3 PRE-FINISH SANDING. When build- ing a project, I sand parts and assemblies all along the way as I’m working. But this doesn’t mean that once the project is complete, no further sanding is necessary. Before applying the stain or finish, I go over the entire project with a thorough pre-finish sanding. The goal is to create a consistent surface that will accept the finish evenly.
You may have scrubbed (with water) or scraped away glue, steamed out a dent or filled a ding. If these areas aren’t sanded, they’ll take a stain or finish differently than the surrounding area. A good once over with 180-grit sandpaper will “level the field.”
At this stage, hand sanding is the way to go. You have better control. For large, open flat surfaces like a chest or tabletop, I wrap the sandpaper around a padded sanding block. For contoured or hard-toreach corners, folded sandpaper works best, as shown above.Since many surfaces won’t need much attention, you can work quickly. But try to be thorough. Sand into the corners and don’t overlook the narrow edges. Finally, gently ease any sharp edges. They’ll hold the finish better and be less prone to damage.
4 REMOVE THE DUST. Now it’s time for cleanup. Before you lay on a finish, you need to remove all the sanding dust and any other debris that may contaminate it. For me, this is a two-stage effort.
To begin, use compressed air or a vacuum to remove the bulk of the dust. A shop vacuum with a soft brush is the tidier way to get the job done and is my preferred method (right photo). Compressed air may be quicker. But you’ll want to blow off the project in a room separate from where you’ll do the finishing.
A final dusting with a tack rag completes the job (main photo, opposite). The tack rag will pick up any remaining dust or debris and leave you with a clean surface ready for finish. And when the finish goes on, the wood will shine and your efforts will be rewarded.
How-To: Remove Dents with Steam
