Many small woodworking and restoration shops are confined (or confine themselves) to local home centers and paint stores for all their finishing supplies. The question is: What can you still accomplish when all you have available is the somewhat-limited selection from these stores that typically cater to the mass public and professional painters?
The answer: Quite a bit, actually. You might be limited in some decorative tools (for example, dyes and toners), but you can still get all of the following:
- Protection and durability ranging from minimal to the best possible
- A sheen ranging from gloss to dead-flat
- Finishes ranging from amber to colorless
- A near-flawless finish resembling sprayed lacquer, but without a spray gun
- Elimination of blotching from stains
- A glaze substitute
- A grain-filling option
- The ability to block off problems in the wood
Protection and durability
You have control of the amount of protection and durability you get simply by how much you build your finish and by your choice of finish type.
Protection means resistance to moisture penetration into the wood. All finishes provide better resistance the thicker they are, so the finishes that harden well and can be built up on the wood are capable of much better protection than oils and waxes that don't harden. Just be sure to apply several coats to build a film.
Durability is the resistance of the film itself to damage from abrasion, heat and solvents. Polyurethane varnish, which is available everywhere, is as durable as any finish.
If you spray finishes, you might have a paint store in your area that carries catalyzed finishes. These also provide maximum durability.
Water-based finishes are slightly less durable, and lacquer and shellac are significantly less durable.
The color you get on the wood is partially caused by the finish. Finishes differ in how much yellowing (or orange) they add.
Amber shellac adds the deepest orange color. Boiled linseed oil and 100 percent tung oil have a slight yellow color to begin with. Then they yellow significantly as they age. Oil-based varnishes, lacquer and clear shellac also have a slight yellow tint, which might darken a little with age. Water-based finishes are the most significant for color because they aren't - and don't - yellow at all.
It's rare to find finishes with sheens other than gloss and satin, but you can use these two to achieve any sheen you want.
Sheen is the amount of gloss, or reflection, in a finish. If no flatting agent is added - that is, there's nothing at the bottom of the can to stir into suspension before application - the finish produces a gloss, or sharp image clarity. The more flatting agent added, the less reflective the finish.
To get a sheen in between gloss and satin within any finish type, simply mix the two (after stirring the satin, of course). To get a sheen flatter than the satin, let the flatting agent settle (don't let the store clerk shake the can) and pour off some of the top. What is left will be much flatter. You can then mix these to get something in between if you want.
Because it is the top, or last, coat applied that is responsible for determining the sheen, you can change the appearance simply by applying another coat with a different amount of flatting agent.
Spray guns can be used to produce nearly flawless - meaning almost perfectly level - surfaces. But you can achieve the same without a spray gun simply by thinning the finish or using an aerosol. The thinner (meaning "thinned") the finish, the better it levels and the faster it dries.
Better leveling means no brush marks. Faster drying leads to reduced dust nibs.
To get a thicker build with fewer coats, brush several full-strength coats and then sand the surface level up to 400-grit sandpaper. Finally, apply several thinned coats or spray from an aerosol.
Blotching is uneven, and usually ugly, coloration caused by stains penetrating unevenly.
To avoid blotching on softwoods such as pine, use a gel stain. For hardwoods such as cherry, birch and maple, a wash coat works better.
A wash coat is any finish thinned to about 10 percent solids content. The type sold at home centers and paint stores is varnish thinned with about two parts mineral spirits. It's called "wood conditioner" or "stain controller."
When you apply this wash coat, be sure to let it dry at least six hours, better overnight, in a warm room or it won't be very effective. This is different than the directions on the cans, which usually say to apply the stain within two hours.
Colored glazes are used to add highlighting, antiquing or create faux graining over at least one coat of finish. Colored glazes are not widely available, but you can substitute a gel stain with excellent results. Glazes and gel stains are essentially the same thing anyway - a thickened stain.
To do glazing, brush or wipe the glaze or gel stain between coats of finish, then remove all the color you don't want using a rag, brush, sponge, graining tool, steel wool or any other tool that produces the results you want.
Some woods look better with their pores filled to create a "mirror-flat" surface. Mahogany is the best example.
Products called "paste wood filler" or "grain filler" (not the same as wood putty) designed to achieve the filling aren't widely available. But you can achieve the same result by sanding a number of coats of finish down to the deepest level of the pores. You can sand a little between each coat or more after all the coats.
For the easiest sanding after a number of coats, use black wet/dry sandpaper with a mineral-oil or mineral-spirits lubricant. Begin sanding with a grit sandpaper that levels efficiently without creating larger-than-necessary scratches (for example, 220 to 400 grit), then sand to finer grits if they are available.
It finer grits aren't available, apply one more coat of thinned finish (so it will level well), spray with an aerosol or rub the surface with 0000 steel wool. You can use a wax, oil or soap-and-water lubricant with the steel wool to improve the smoothness.
Problems in the wood
Of all the finishes, shellac is easily the most effective for blocking problems in the wood. The most common problem in new wood is resinous knots in pine and other softwoods. The resin can bleed into the finish and cause it to remain tacky and not cure.
In old (refinished) wood, the most common problems are fish eye (cratering or ridging) and odors from smoke or animal urine. Shellac blocks all these problems; you can then successfully apply any finish over it. If there are no problems to block off, there's no reason to use shellac as a first coat.
Bob's new book is "Flexner on Finishing."
This article originally appeared in the March 2011 issue.