No doubt woodworkers were inspired centuries ago to try coloring their wood with natural dyes after observing the range of hues they imparted on fabrics. We tend to think of natural dyes as coming from plants, but of the four most popular dyes used to color wood nowadays, two of them, brazilwood extract and logwood extract, are derived from the heartwood of trees, one is derived from the husk of a nut or from peat (walnut crystals) and the fourth, cochineal, is actually a bug.
Like chemicals, natural dyes get a color boost from tannic acid. Unlike chemicals, however, they will still deposit a more colorful shading (as opposed to the weathered effect of chemicals) on wood that does not contain tannins.
The main advantage that natural dyes have over synthetic dyes is that they are more light fast when used in conjunction with a mordant. So before you get too excited about the prospect of coloring your wood in a more natural way than using chemicals, let us explain the concept of mordants.
The word “mordant” comes from the Middle French word “morder” which means “to bite.” A mordant is the fixer that helps the natural dye’s color bite more firmly into the wood’s fibers . . . or you could say, the mordant binds the color to the fibers. Chemicals are the mordants for natural dyes. The most common chemicals used as mordants are potassium dichromate, ferrous sulfate and alum. If you want to use a less toxic chemical as a mordant, try sodium carbonate and see if you like the results. Mordants are not essential for all natural dyes, as you will see in two of the following recipes (brazilwood and walnut crystals).
When chemicals are used as a mordant with natural dyes, tannins are not essential. Chemicals will still bind the natural dye to the wood even if the wood does not contain tannins.
If tannins are indeed present, though, the chemical mordant will do more than interact with the dye color and help bind the color of the natural dye to the wood fibers. Now the chemical will add an additional twist to the final color because of the chemical’s reaction to the tannins.
So the irony is that chemicals require an organic substance (tannins) to be present in the wood in order to be their most effective, and natural dyes require a chemical (as a mordant) in order to produce their most dramatic color change.
The traditional method of application is dye first, followed by a chemical mordant. If, however, you are adding tannic acid to the wood (yet another variable on species like alder and maple that contain little to no tannins), you would begin with the application of the tannic acid solution and—after the wood is completely dry—proceed to applying the dye. However, there is no need to re-apply the tannic acid solution before adding the chemical.
Because you dissolve natural dyes in water, use a synthetic brush to apply them. They are typically non-toxic but they will stain your skin, so wearing gloves is a good idea.
You can see that the intersection of chemicals and dyes vastly widens your choices for coloring wood. The combinations presented here are some of our favorites but feel free to experiment, and even design your own signature combination!
Always keep track of the number of passes you made when coloring with a natural dye so that the color intensity remains consistent.
Tea as a Natural Dye
From time to time you hear about the potential of tea to color your wood, and indeed it will—but not dramatically. Compressed tea is best because it produces a more concentrated color. In our experiment with it, we steeped twenty-four ounces of compressed pu-erh (black) tea, the amount intended per the instructions to fill forty-eight teapots, in a mere three cups of water for eleven hours. The results produced a decidedly minor blond effect.
Tea is loaded with tannins, however, so it will serve as a booster if used in conjunction with other natural dyes or chemicals.