A wood stain is a colorant (pigment or dye) and a binder (some sort of finish) with a lot of thinner added so the excess stain is easy to wipe off. This leaves some color in or on the wood.
A stain can also be just dye and thinner with no binder added.
Pigment is ground earth or colored synthetic particles, so it requires a binder to glue it to the wood. Pigment settles to the bottom of the can and has to be stirred into suspension before use.
Dye is a colorant dissolved in a liquid, so dye penetrates along with the liquid and doesn’t need a binder. Coffee and tea are examples of weak dyes.
You don’t need to use a stain unless you want to change the color of the wood. If you do apply a stain, you do it before applying the finish.
Types of stain
Common categories of wood stain include the following:
• Oil stain (thins and cleans up with mineral spirits).
• Water-based stain (thins and cleans up with water).
• Gel stain (thick like mayonnaise, it spreads and wipes off easily like mayonnaise).
• Dye stain (a colorant dissolved in a liquid).
• Combination stain and finish (doesn’t color as effectively and is streaky with brush marks if brushed and left).
• Lacquer stain (a very fast-drying stain that’s sprayed and wiped quickly; often applied by two people).
• No-wipe stain (a fast-drying stain thinned enough so it can be sprayed and left without wiping).
The primary differences in stains are as follows:
Ease of application — Oil stains are the easiest to apply because you have plenty of time to wipe off the excess. All the other stains dry quickly so you have to work fast or on smaller areas at a time.
Drying time — Lacquer stains, no-wipe stains and dye stains dissolved in solvent (not water) can be coated over within minutes. Water-based stains can be coated over after about an hour. Gel stains, and dyes dissolved in water, require four to six hours before coating over. Oil stains should be allowed overnight drying.
Grain definition — All stains provide good grain definition if the excess is wiped off because more colorant is left in the grain. Dye stains produce slightly less definition than pigment stains. No-wipe stains produce no grain definition.
Color control — Dye stains provide the best control of color — that is, getting the color darker without obscuring the figure of the wood. Dye is see-through; you can apply as many coats as you want and still see the wood’s figure. Pigment hides.
Conditioning the wood
The purpose of “conditioning” or “washcoating” wood before applying a stain is to reduce blotching, which is uneven coloring caused by irregularities in the wood. A wood conditioner or washcoat is any finish thinned to 5 to 10 percent solids so it doesn’t totally seal the wood. Some of the stain can still penetrate.
The woods that blotch are softwoods such as pine and tight-grain hardwoods such as maple, birch and cherry. There’s no point in applying a wood conditioner/washcoat to medium- or coarse-grain woods such as walnut, mahogany or oak.
Lacquer and shellac washcoats dry rapidly, so they are the most efficient to use.
Varnish wood conditioners (the common ones found in home centers and paint stores) are varnish-thinned with about two parts mineral spirits (paint thinner). You can make your own. The key to getting the varnish wood conditioner to work well is to let it dry fully before applying the stain — at least six hours, better if overnight. This is different from the directions on most cans.
The basic rule for applying all stains except no-wipe is to apply a wet coat and wipe off the excess before the stain dries. Unless the wood is naturally blotch-prone or you haven’t sanded the wood well enough to remove all mill marks and other flaws, you will always get an even coloring.
You might need to divide your project into smaller sections or have a second person wipe as you apply to get good results using one of the faster drying stains. It’s much faster to spray the stain onto the wood or wipe on with a cloth, wearing gloves of course, than to brush it.
Common problems and ways to avoid them:
• The stain dries in spots before you get it all wiped off, leaving an uneven coloring. If you are quick enough, you can wipe with more stain on smaller sections at a time to reliquify the stain so you can then wipe it off evenly. Otherwise, strip with lacquer thinner, acetone or paint stripper and restain smaller areas at a time or get a second person to help.
• The color of the stain doesn’t match what you expected from the name on the label. Names are simply manufacturer’s interpretations. There are no industry standards.
• The color of the stain on your project isn’t the same as on the color sample in the store. Woods color differently. Always try the stain on scrap from your project and make adjustments (add pigment or thinner) if necessary to get what you want.
• Glue from squeeze-out or fingerprints seals the wood preventing stain penetration. Sand or scrape off the glue through the stain and restain that area or leave the splotch and disguise it by painting in the correct coloring after you have applied a coat of finish.
Stain problems such as blotching and getting the color wrong can be extremely difficult to fix. You can usually remove some of the color by wiping with the thinner for the stain. If the stain contains a binder (it isn’t simply dye), you can use a paint stripper. But nothing short of sanding will remove all the color.
Flexner is author of “Understanding Wood Finishing” and “Flexner on Finishing.”