PIGMENT STAIN PIGMENT OVER DYE DYE STAIN
In my last column, I showed you how dye stains and linseed oil can bring out the figure of closed-pore woods. (See AW #63.) To achieve this with open-pore or coarse-grain woods, we use pigment stains.
Coarse-grain woods like oak, ash, butternut, mahogany, and lauan have pronounced, often beautiful grain patterns. These patterns are formed by the contrast between earlywood and late-wood in each growth ring. Earlywood tends to have large (open) pores, while latewood has smaller (closed) pores.
The best way to highlight these grain patterns is to darken the large pores so that they stand out against the surrounding tighter-grain wood.
Pigment particles are vastly larger than dye particles. Pigment will collect in the large pores, but tends to wipe off tight grain without leaving much color. The result is a more vivid contrast between the earlywood and latewood. That does not mean there is no place for dyes in treating coarse-grain woods. But let's deal with pigment stains first.
When you apply a pigment stain, leave as much stain on the wood as you like. If you wipe it ofT vigorously before it dries, you'll remove most of the color from the tight-grain areas and leave the dark color in the open pores. If you wipe the stain off gently, you can leave more color on the tight-grain areas. But pigments are opaque, so leaving too much stain on a surface will obscure the wood. This level of control makes these stains very versatile. When we set out to enhance the grain pattern, our object is to wipe off as much stain as possible, leaving a copious amount only in the open pores.
There are some stains on the market that contain nothing but pigment. They are sometimes called "wiping stains," or may say "100% pigment" on their labels. But most commercial stains are mixtures of pigments and dyes. For these techniques, we'll need "pigment only" stains. If you can't find them in the store, you can create your own pigment-only stains.
Pigment stains consist of ground-up, colored "dirt" (actually mineral particles) suspended in a liquid. In order to keep the "dirt" on the wood once the liquid dries, they all contain "binder," a film-forming material that glues the pigment to the wood. In most cases the binder is some type of drying oil like boiled linseed oil.
Mixing your own stain is quite simple. Buy artists' oils or Japan colors, which also contain oil, at your local art supply store or woodworking specialty store. Mix whatever colors you need to get the color of stain you want, and dilute them about 50% with either naphtha or mineral spirits. Of the two, naphtha evaporates a bit foster.
Using a slower solvent like mineral spirits to dilute the stain gives you more time to wipe it off or manipulate it. The solvent affects how quickly stain dries to the touch, but no matter how fast it dries, the oil in it still has to cure overnight.
Test the mixed stain on a sample board, and adjust the color by mixing in other pigments. You can reduce the intensity by diluting with more solvent.
Because pigmented stains always contain a binder, they act like thinned paints. In fact, you can use rhinncd-out paint as stain. That means you can wipe, spray, or brush them onto the wood and wipe off as much or as little as you want.
With some woods, simply staining the raw wood with a pigmented stain will do the trick. Try staining a flatsawn plank of oak or ash with a pigmented stain. Wipe it on and wipe off as much as you can while it is still wet.
You will notice that the stain barely colors the wood except for the deep pores that make up the cathedral pattern. (See left photo, above.) The darker the stain color, the more distinctly the cathedral grain pattern will stand out.
If we stained the same board with a dye, the opposite would occur. (Sec right photo, above.) The ash or oak would take color almost uniformly, and the cathedral pattern would be less obvious.
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