Understanding Stains

Lacquer Stain
Lacquer stains use very fast-drying binders and solvents. Professional finishers often choose these types of stains because the finish can be applied within approximately 30 minutes, and the stain
can be added to lacquer to make a “toner” for adjusting color between coats of finish.

You can identify lacquer stains by the strong, pungent odor caused by solvents such as xylene and various ketones, which will be listed on the cans.

Lacquer stains are difficult to use because of their very fast drying. Professionals usually work in pairs, with one person spraying the stain and the other following right behind wiping off the excess.

Choose a lacquer stain if you are spraying and want to reduce the time between staining and finishing, or if you plan to add a colorant to your lacquer.

NGR Dye Stain
NGR stands for “non-grain-raising” and refers to a type of dye that’s usually dissolved in very fast evaporating solvents. As with lacquer stains, NGR dyes are favorites with professional finishers because there is little waiting between staining and finishing and the stain can be added to lacquer to make a toner.

All NGR dyes are packaged in liquid form and most contain methanol and sometimes other toxic solvents. No pigment or binder is included. Some NGR dyes are packaged in concentrated form and can be thinned with water, alcohol or lacquer thinner. (If thinned with water, they perform closer to the water-soluble dyes discussed below.)

Choose an NGR dye stain if you want a deeper or more even coloring than can be achieved with pigment. Also choose NGR if you want to reduce the time between staining and finishing or add a dye colorant to lacquer to make a toner.

Water-, Alcohol- and Oil-soluble Dyes
These dyes are packaged in powder form, which makes them easy to identify. You have to dissolve them in the proper solvent.

Of the three, the most useful is water-soluble dye because it provides more time for wiping off the excess and there’s no exposure to irritating solvents. (Handle grain raising and fast drying the same as with water-based stains, described earlier.) Alcohol-soluble dye is sometimes used by touch-up specialists precisely because of its very fast drying. Oil-soluble dye is rarely used anymore (except in oil stains). It’s been replaced by NGR dye.

Choose a water-soluble dye if you want deeper or more even coloring than can be achieved with pigment. PWPigment and dye are the two primary colorants used in stains (chemicals being the other).

PIGMENT AND DYE

Pigment is ground earth or colored synthetic particles sized to imitate earth. The particles have weight so they settle to the bottom of the can if not kept in suspension by stirring.

Dye is a chemical that dissolves in one or more specific liquids (different dyes dissolve in different liquids). So dye becomes a part of the liquid and doesn’t settle out.

You can tell if a stain contains pigment, dye or both by inserting a stirring stick after the stain has sat undisturbed on a shelf for several days or weeks. Pigment will have settled to the bottom; dye will still be in solution.

Because pigment has size it can’t penetrate into wood. But after you wipe off excess stain, some pigment remains in pores and sanding scratches that are larger than the size of the pigment particles. This explains why sanding to finer grits produces a lighter coloring: less pigment can lodge.

Because dye dissolves in a liquid, it has no size and penetrates along with the liquid. So dye colors wood more uniformly.

You can’t endlessly darken wood with pigment unless you leave some to build on the surface (equivalent to painting). But dye can be applied in many coats to darken wood as much as you want without obscuring the wood or creating any build – as long as there is no binder in the dye that would itself build.

Dyes that don’t build are NGR, water-soluble, alcohol-soluble and oil-soluble. Oil, varnish, water-based, gel and lacquer stains with dye included to add build.

All dyes, whether dissolved in solvent or containing an added binder, fade in bright light, especially sunlight and fluorescent light. You should avoid the use of dyes if your project will be placed in these conditions.



When excess stain is wiped off, pigment lodges in pores and sanding scratches highlighting them (left) while dye penetrates everywhere along with the liquid and colors more evenly.

— BFAll types of stain can vary in color intensity depending on the ratio of colorant (pigment, dye or chemical) to liquid (oil, varnish, solvent, thinner, etc.). The higher the ratio of colorant to liquid, the darker the stain colors the wood. You can change the ratio in any stain by adding pigment, dye or thinner.

COLOR INTENSITY

Sometimes you hear that you can make wood darker by leaving a stain on the surface longer before wiping off the excess. The explanation given is that the stain penetrates deeper. This is not true. What happens is that more thinner evaporates increasing the ratio of colorant to liquid.



The color intensity of a stain is determined by the ratio of colorant to liquid. A full-strength commercial oil stain darkens wood more (left) than the same stain thinned 50 percent with mineral spirits (right).

— BF

For a chart on choosing the right stain, click here:
Choosing the Right Stain chart.pdf (159.54 KB)

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