Gazette Archive 3/27/01
Homemade and Alternative Stains and Colorant by Jim McNamara
Woodworkers and finishers, like you and me, are often interested in making colorants and finishes at home, sometimes from common household products or from simple chemical mixtures. This is a discussion of a few selected recipes along with some of the science behind them.
The colors some of these homegrown finishes produce are not very colorfast, either, compared with modern dyes and pigments. There is a reason we use more modern chemistry when we use modern finishes. The results, in general, are far superior to materials and methods available 200 years ago.
Pigments and Dyes
Pigments are very small particles
that reflect colors. Because they are particles, they will actually
stop light from passing through, if there are enough of them.
Paint, which is opaque, is made from pigments. If you apply
paint to glass it will block the light coming through the glass.
Pigments are usually manufactured, but there are lots of natural
Dyes are different from pigments. They are not small particles, but are molecules, which are infinitely smaller. If you completely dissolve a dye in water, light will still pass through the water. This is because molecules of dye do not block light, they absorb some colors and let others pass on through. For example, woad, a plant product, is a natural dye. Natural dyes are mostly derived from plant or animal sources. Navajo Indians still use some vegetable dyes to color wool for rugs and blankets. Other natural products like sheep urine or shellfish exudates were also used. In case you're curious, sheep urine makes a pale bluish color and it doesn't work on wood. Generally speaking, most natural dyes produce very limited color intensity. This is unlike the bright manmade dyes we commonly use to color fabric and sometimes wood.
And please note - just because something is a natural product does not mean that it is necessarily non-toxic. For example, the pigment Paris green is based on copper and is extremely poisonous. It's even used as rat and bug poison. Natural does NOT equal safe, all the time. Be sure to always wear protective gloves and eye protection, even if you think what you are doing is fairly safe.
The other important note is that some processes are not predictable. For example, you can apply an iron and vinegar solution to oak and get very different colors. They may range from silver gray to dark brown. Each tree seems to react differently. You will need to experiment on scrap first before you ever consider employing any of these recipes as part of a finish on a real project.
You may also want to raise the grain on the wood and sand very lightly first. This is because a lot of treatments involve using water.
There are two ways to color
Altering Wood: Sunburned
Purpleheart turns brown but does so much more rapidly in direct sun. White pine becomes yellow-orange in two or three days of intense sun, in the same way cherry darkens. Orange white pine is referred to as pumpkin pine. Pumpkin pine is what you see in old furniture made from white pine. Again, this is a way to get simulated aged wood.
In general, the action of ultraviolet light on wood acts to move the natural color of the wood the 'other direction'. Walnut becomes tan, teak silver, and pine yellow-orange. As a rule, dark woods fade, and pale woods gain color. This is part of the esthetic value people place on antique wood.
Since wood has only a small amount of extractives present, the total possible amount of color shift is usually pretty limited. More exposure to UV light does not create proportionately more color change. There is always an end point. For cherry, it is generally about 4-8 hours in direct sunlight, for example. Sun exposure is not a practical approach for coloring some species of wood like elm or ash, unless you are very patient. Plus, any subsequent surfacing of the wood removes the sunburned color because it is only skin deep to start with. Leaving wood outside uncovered for long periods also causes ultraviolet erosion of the wood. UV erosion will rough up the surface as well. This means resurfacing may be required, undoing the ageing effect.
Altering Wood: UV Damage
High temperature storage, maybe in an attic in the summer, will also darken cherry wood over a period of time. Heat also speeds color changes in many oily tropical woods, like teak, rosewood, or zebrawood. Other species like oak are generally unaffected.
Altering Wood: Tannins
Adding tannins is simple. Get regular orange pekoe (Lipton's) or other dark tea. Steep about 10 tea bags in 1 qt hot water. Put the bags into boiling water, then turn off the heat and let it sit for about 2-3 hours. Remove the bags, being sure to squeeze out liquid from each bag. Apply an even coat of the tea-saturated water to any species of wood. Wipe completely dry, then allow the wood to dry overnight.
Tea is high in tannins, plus it also adds a small amount color. This tannin enhanced wood reacts vigorously with iron acetate as described below. You can use tea on woods that contain no tannins, and treat the surface just like it was oak to start with. Adding a lot of dark tea also creates an aged, slightly grungy look on species like willow and elm. These species seem to get more color change from tea. This, without any iron treatment.
Tannins react with metals like iron. Soak a pad of fluffed-out, oil-free fine steel wool in 2 cups of clear vinegar at least overnight. To make oil-free steel wool, rinse the steel wool in thinner, then let the steel wool dry fully. Vinegar reacts with iron in the steel wool to make iron acetate. Apply your vinegar solution to any tannin bearing wood, like oak. Also, apply your iron solution to any wood that has been treated with tea.
The resulting color usually looks like aged oak. It ranges from a silvery gray to a dark brown, depending on the amount of tannins present, the concentration of iron acetate, and other factors. Iron salts applied to many species has little or no effect, and now you see the reason why. The quick way to see the effects of iron is to look at old construction or old furniture where nails or iron hardware contacts the wood. If you see dark zones around the nail or hinge, then the wood species does react with iron to create color.
Altering Wood: Ammonia
Traditional fuming of oak must be done in specially constructed plastic tents with concentrated ammonia (26%). This is EXTREMELY nasty stuff to handle. Consider something else.
The something else is household ammonia. You can achieve some darkening of oak by using soap-less household ammonia, straight from the bottle. Do this ONLY in a really well ventilated area with a fan blowing across the work to push the ammonia fumes away from you and outside. Ammonia fumes are horrible. Be careful. Simply apply the ammonia with a rag or brush, let it stand until it has evaporated, then wash the surface with very dilute vinegar. This neutralizes the ammonium hydroxide left behind from the ammonia solution. Wash off with plain water and let dry. This is messier than fuming but gives some of the color. If you want to try fuming, Taunton Press has published information on finishing practices, and one of them is about fuming.
Altering Wood: Lye
Dissolve 1 tsp of lye (Red Devil works fine) in about 3 cups of cold water. Be aware that lye solutions are caustic, and if they remain on wood for fairly long periods of time it will result in damage to the wood surface, making the wood appear fuzzy. One-half hour with dilute lye will do no damage. However, stronger caustic solutions may break wood fibers loose.
Leave the lye solution on the wood only until you have good color, usually just a few minutes. The color change happens faster in really warm temperatures. Next, neutralize the surface with dilute vinegar, and finally, wash with plain water. The color will continue to darken slightly more for a few minutes, even though lye is no longer on the surface. Longer exposure to lye will yield somewhat darker colors, up to a point, then no further perceptible darkening occurs. This process absolutely requires testing on scrap first.
Altering Wood: Household
Household bleach will also lighten some species of raw wood slightly, generally the darker species like mahogany, walnut, and black or red oak. The amount of lightening is fairly small. Inside, or in the shade, apply liquid bleach with a rag, right out of the container, and let it stand until it dries. No rinse is required unless you plan on adding a commercial dye on top of the bleach. Consider using bleach on oak if it looks somewhat variegated - dark and light areas on one board. Bleach seems to even out this sort of problem pretty well. This is because it seems to work more effectively on the darker zones.
Altering Wood: Pharmacy
You must wear gloves and protective gear!
Potassium permanganate can also be applied to wood species that are low in tannins. It is toxic, as well as a powerful oxidant. Use it the same way you use potassium dichromate.
Bichromate of potash (potassium dichromate by another name) is available from www.garrettwade.com and either chemical can be had through local pharmacies, depending on local regulations.
Adding Colorants: Common
Strongly brewed coffee, applied cold to wood, imparts a solid brown cast to most species of wood. Let the coffee sit on the wood surface, with surface constantly wet, for about 10-15 minutes, then wipe thoroughly. Let the surface dry for several hours before applying any other finishes. Coffee that has sat at high (180F +) temperature for long periods of time or is several days old is oxidized and does not work well as a colorant. Freshly brewed, cold coffee works the best.
Since the color extends only a short distance into the wood, a protective clear coat, or even paste wax is recommended over a coffee stain. One really nice feature of coffee staining is that future coffee spills present no problem. Coffee is somewhat lightfast, but will not do for exterior use.
Fruit juices which are high in anthocyanins (purple color in grape juice) will stain wood, but the color pales rapidly to a tan or brown color. They are not recommended for staining.
To get really bright colors, food coloring works very well as a wood dye. The best substrate is a wood that is close to white, like white pine. This allows the color of the dye to show through more clearly without being altered by amber tones in the wood.
This method produces non-toxic, painfully bright colors for children's toys. Adding a clear coat of spray lacquer will improve durability as well as prevent color leakage onto children's hands. Clear lacquer is made from nitrocellulose, the same stuff as cellophane, and is completely edible when fully cured. Food colors are not lightfast, but will last for several years. Red and yellow fade the fastest.
Food colors are available in larger 4 oz jars, avoid the small plastic drop jars which are too expensive for this kind of application. Mix the dye about 5-6 parts water to 1 part food coloring and flood the wood surface for about five minutes. Work out of direct sunlight. Wipe the surface repeatedly to remove any residual dye that has not gone into the wood. After the surface dries overnight, attack it once more with rags to remove any light powdering of color that may remain.
To create secondary colors like orange and purple, mix primary food colors, just like we did back in first grade.
"Rit" brand fabric dyes also work on wood. You have to mix them in hot water, let them stand, soaking the wood surface in the dye solution for about 20 minutes. Rinse and wipe dry.
Adding Colorants: Pigments
and Homemade Wood Stains
You can use this basic recipe, or use a manufactured stain that is almost a non-color, like Min-Wax Honey Pecan. Honey Pecan contains only a small amount of dye and no pigment. To two cups of stain binder you add pigment: 6-8 level tablespoons of wetted pigment or about 5%-10% pigment. More or less can affect color intensity, but this is where to start.
Wetted pigment is the consistency of heavy cream or thin toothpaste. To make wetted pigment, dump out 6-8 tablespoons of dry pigment and about a tablespoon of thinner onto a flat surface, one that will not absorb the thinner. Mix the thinner and pigment into a viscous paste with a putty knife or a spatula. You can also use Japan Colors as a pigment. It is already wetted. Japan colors are available at most home centers, paint stores, and from Woodworker's Supply or www.woodcraft.com
To add the pigment, stir the
stain binder base rapidly while adding blobs of pigment.
Pigmented stains work by allowing pigment hunks to stick in tiny pores and grain imperfections, and to be held there by the binder. Sanding beyond 150 or 180 grit prevents these types of stains from working well. These stains are meant to be applied with a rag or a brush, allowed to stand for about five minutes. Next, wipe off excess stain.
Pigmented stains tend to highlight grain, rather than reduce it. Pigmented stains also have an interesting trait - on some species of wood, like Douglas fir or hemlock, you may see grain reversal. This is because the pigment sticks to lighter areas of wood and not to denser dark areas. After wiping, the dense un-pigmented areas appear lighter than the surrounding heavily pigmented areas. This creates the effect of reversing the grain - what was light is now dark, and what was dark is now light.
Pigments are available as Fresco Colors from Woodworkers Supply, and www.woodcraft.com. Bulk amounts of pigments, which are far cheaper, are available from www.sinopia.com, www.kamapigment.com. Kama Pigments is in Canada, with significant price advantages for US consumers, but you have to use a credit card.
Working with create-your-own stains means that you can create virtually any color, or duplicate an existing color by mixing different pigments. If you need to darken the ground color (the color not from the pigment) you can add wetted oil-soluble dyes to your mix. Oil-soluble dyes are available from www.woodcraft.com, Woodworker's Supply, and www.garretwade.com.
Adding Colorants: Pigmented
To soften the hard paste wax, simply add 1-2 part shaved wax and 1 part turpentine (mineral spirits doesn't work very well) to a jar. More wax makes the final softened wax stiffer. I prefer softer wax, so I use 1:1.
Cover the jar and let it sit
for a few days. Slosh the jar once a day. The softened wax
will be the consistency of toothpaste. Add wetted pigment, at
the rate of 4-6 tablespoons or so per cup of softened wax. You
are shooting for about 10% pigment evenly dispersed into the
wax medium. More is a waste of pigment. Less may not provide
Apply colored wax just like regular wax. It works the same way a stain works, the pigment particles get stuck in tiny pores and are held there by the wax. The main difference here is that wax is easily removed at any time with thinner, because it never hardens like the binder in regular stain.
Shoe wax, like Kiwi brand, is a pigmented wax, too. It comes in a bunch of colors. In practical terms, it gives you a chance to play with pigmented wax without going to a lot of time or expense, because most people have some in a closet somewhere. Kiwi Bois is the brand of professional colored wax the Kiwi people make. It comes in much larger cans. Generally, Kiwi and other shoe waxes are based on shellac wax - the wax extracted from commercial shellac and hair spray.
Adding Colorants: Shoe Polish
Adding Colorants: Homemade
Glazing Stain (gilp)
The open time on this gilp is about 3 hours at 70F. So, you need to rub off what you want or wipe off the entire application with a solvent soaked rag, all during that time.
Basic Gilp or Glazing Stain
Wet the chalk with the turpentine, then mix the wetted chalk into the linseed oil. Add wetted pigment, then add the drier last. Turpentine acts to stimulate drying. If you use mineral spirits instead it will extend the open time of the glazing stain, but it will increase the overall cure time.
Add the pigment just like you would for the basic stain recipe. Kept tightly sealed, the glaze has a shelf life of about 4-5 days. Mix up only as much glaze as you can use in one or two sessions.
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