Wood Conditioners

By Bill LaHay

Wood conditioners provide a partial sealer coat on the wood surface so that stains penetrate more evenly and yield a more uniform color or appearance.

Why are they necessary? Basically, because wood is an inconsistent material. Two boards from the same tree, or two sections of the same board, can vary in porosity, color, and density — all of which will affect how the wood reacts when a stain is applied. Pine, fir, spruce, alder, birch, and maple are among the light-colored wood species that are prone to this uneven coloring, sometimes called splotching.

Wood conditioners are essentially thinned varnishes that fill some of the tiny pores and crevices between the wood fibers. These spaces are where the color pigments collect when a stain is applied, and they are not distributed evenly throughout the board’s surface.

As a result, areas with more porosity collect more pigment and thus take on a darker, more intense color. Also, areas where the wood fibers change direction tend to be more porous and absorbent.

When a wood conditioner is applied, the varnish solids settle into the wood pores and partially fill them, preventing excess amounts of stain pigment from gathering there later in the finishing process. Manufacturers and even wood finishing experts differ in their guidelines for how long you should wait to stain after using a wood conditioner, but as a rule, allowing the conditioner to dry or cure overnight will make it more effective. If you apply stain while the conditioner is still wet, the pigment is more likely to blend into or even penetrate the sealer coat. The photo to the right shows one solid board with half stained using a conditioner (left), and half stained without a conditioner (right).

If you can’t use a wood conditioner on your project or want even more control over the wood tone and color, you can use a gel stain, which due to its thicker consistency won’t allow the pigment to settle into the wood pores so readily.

By blocking pigment penetration, the use of a wood conditioner means the stained wood will not only appear more uniform but also lighter in color. As with any finishing technique, practice on some project cutoffs or scrap wood of the same species and similar density. Also, be aware that a hardwood-veneer plywood face will stain lighter than any solid wood trim you might apply along the edges, because the glue line behind the veneer will block pigment penetration. To compensate, you might have to apply a wood conditioner to just the solid wood edging.