In some cases, however, this phenomenon is not desirable, especially if it is not consistent throughout a particular surface or product. In these cases, the overall affect just looks blotchy. Some wood species such as maple, cherry and birch are notorious for this. The challenge is to control the blotchiness while obscuring the grain as little as possible.

 

In order to illustrate the potential difference in color between the lighter areas and the darker, or blotchy areas, we can look at the most extreme example. That is, the difference between the face of a straight grained sample and the end grain. The difference becomes much more dramatic when we apply a stain, especially if we flood the surfaces with a dye stain and then wipe off the excess. The end grain, of course, becomes much darker due to a greater rate of absorption. This disparity in absorption rate is basically what causes blotchy surfaces when we stain.

 

There are several techniques we can use to mitigate the blotchy affect.

 

One very effective technique is to use a pre-stain, also referred to as a wood conditioner. A pre-stain is basically a stain base with no colorant but it should contain a binder that will dry and harden. If it doesn’t contain a binder, the stain will need to be applied before the pre-stain evaporates. By flooding the surface with a pre-stain and wiping off the excess before it dries, more pre-stain is absorbed into the areas that would normally absorb more stain. This process blocks the stain itself from absorbing excessively into those problem areas. The result is a more even color with virtually no clouding of the grain. If you plan to use a water-based stain or sealer, using a water-based pre-stain is a good idea since the water will raise the grain and the binder will hold the grain stiff so that it can be sanded smooth prior to staining.

 

Applying a wash coat of sealer or glue sizing before staining will have an outcome similar to pre-staining but will be less effectual since the amount of material that remains on the surface is more consistent throughout. The more absorbent areas are blocked from absorbing stain only as much as are the less absorbent areas. When stain is applied, less stain will be absorbed overall but the disparity in absorption rates from one area to another will not be rectified.

 

Another method of controlling blotchiness is to spray-to-color using dyes, pigments or a combination of the two. Dyes are best for retaining the clarity of the grain. A limited amount of color is applied evenly to the surface.The problem areas never get a chance to absorb more colorant than other areas. This method results in a more even color than pre-staining but at the same time, it has a tendency to tone down highlights in the wood altogether, creating a more monotone appearance. For best results, the colorant should be applied sparingly. Additional color can be applied if necessary by staining, glazing or tinting.

 

The most extreme method (aside from painting) is to spray a toner on the surface. A toner is a sealer or topcoat with a substantial amount of pigment and/or dye added. It masks color variation in the wood along with most of the grain characteristics. Sometimes a toner that’s lighter in color than the wood itself is used, allowing translucent shades of color to be applied on top, creating a kind of artificial depth to the finish. This technique is often used in high production situations where careful wood selection is impractical.

 

In some cases, most notably with cherry, I’ve seen oil-based pigments applied directly to the wood where they do a good job of controlling blotchiness while allowing other features of the grain to show through. The annual rings in particular remain apparent while the blotches blend in well with the surrounding wood.

 

It’s a good idea to experiment with some samples of wood similar to what you’ll be using on a given project or product to see what works best for you.