|Fundamentals of Finishing Archives
Getting 'Dry and Dirty'
A look at two techniques for brushing out dry and paste colorants.
By Mac Simmons
In this column, I present two finishing techniques that have been around for decades, yet they are not well known by many finishers, refinishers or restorers. They are "dry and dirty brushing."
As you can tell from their names, both involve a brushing application. The dry brushing technique uses dry powder colors, while dirty brushing uses pigmented paste colorants. Both can be an option or backup if you run into a problem. Through the years, they have gotten many of my customers out of a jam.
These techniques do require some trial-and-error practice in order to become proficient. I also suggest that you become familiar with the main furniture colors, like Van Dyke brown, burnt umber, raw umber, burnt sienna, raw sienna and French yellow ochre, although other colors may be needed to achieve certain shades. A detailed explanation of the two techniques follows.
This method can use any of the dry pigment powders, including Fresno dry powders or Lake concentrated powders. In preparation for application, wood should be sealed or finished, since the sealer or clearcoats will prevent the powders from entering and penetrating the wood.
To explain how and why dry brushing is done, here is a mock scenario: Let's say you have finished some pieces of furniture, using the same materials throughout the finishing process. Some areas of the wood look lighter in color, while other areas have a different color hue, and all these areas are very obvious and not acceptable.What you have is a result of the basic variations of color. Normally, a shading gun, airbrush or aerosols could solve the problem. But in this instance, let us say you do not have these items at hand, or you already tried them on a test area and were not happy with the results. So you decide to try "dry brushing" to solve the problem.
You start by selecting a dry powder that will blend well with the finish and can be combined with other dry powders, if necessary, to achieve the proper color. They should be thoroughly mixed and blended into a uniform color. I suggest you begin by making a complete sample, including a sealer or your regular clearcoat, and allow the coating to dry completely.
Start with only one color to practice. Spoon a small pile of powder onto some newspaper -a half teaspoon will do as a starter. (Remember, wear a dust mask.) Take a flat 2-inch or 3-inch brush, dip it into the dry powder and work the brush back and forth on some newspaper to achieve a uniform color. Then take the brush and begin to work it across the wood surface, going back and forth. This will give you the feel of the technique and you can see the effect of the color.If too much powder is brushed out, use a clean brush to pick up the excess. Once you have a uniform distribution of the powder on the panel, apply a very light misting to seal the color and allow it to dry. Repeat the process for practice and include some practice on smaller areas.
If the powder is brushed beyond the areas that need color, use a clean piece of cloth to wipe off and blend the excess powder. Then lightly apply the mist coats and allow for drying. Always end the process with clearcoats that will flow out the finish and coatings. (See Photo 1 above for an example of dry brushing on a scalloped edge.)
For this technique you can use any of the pigmented paste colorants, like universal, oil colors, Japan colors, acrylics or water, as long as they are compatible with your clearcoats. Start by taking out or squeezing out some colorant from the container or tube and place it on some newspaper. Then follow the same instructions as for dry brushing, working the flat brush on the newspaper until it is loaded and the color is uniform.
If there is too much color on the brush, you will block out the wood's grain. In some cases, a small amount of a compatible solvent may be added to adjust the consistency of the colorant to make it more workable. You should spend some time making up complete samples to get the feel and see the results from dirty brushing. (See Photo 2 above showing the dirty brushing process.)
Which method you choose may depend in part on your desired result. If you want transparency in your finish, dry brushing will give you greater clarity. Paste pigmented colorants will give you translucency or opacity.
Possible Uses and a Final Tip
You can use these brushing techniques to make color adjustments on surfaces, rubbed-though edges, scallops, grooves, rosettes, carvings, routings, jointed woods, for blending in heartwood and sap wood (see Photo 3 below), to add age markings and for many other color corrections.
Finally, I remind you again to apply a clearcoat to your samples or practice runs in order to judge the final color correctly. You cannot see the true colors of brushed powders or paste colorants unless you apply a clearcoat over them.