Stains and Dyes
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Wood has been stained with coloring agents of all
descriptions for nearly as long as people have been working with wood. It
comes naturally in a nearly endless variety of colors and textures, but many
highly prized species are also difficult to obtain, and costly.
As a result, it is often desirable to alter the appearance of a more common
wood to make it look like a more valuable or exotic species. Sometimes,
color is used to enhance the natural properties of the wood, making the color
and texture of the wood more apparent. And sometimes, a stain is used
to mimic the appearance of aged wood, or to blend new construction into
preexisting cabinetry. For all of these purposes, finishers have their
choice of just two basic ways to color wood: stains and dyes.
A stain is very much like a transparent paint: it consists of a pigment (finely
ground particles of solid color) suspended in a solvent with a varnish resin
binder, which "glues" the particles to the surface. Since they use
opaque particles deposited onto the wood's surface, stains tend to obscure
the wood grain like a thin coat of paint, and multiple coats could result
in an opaque color. Also, since the stain will be left thicker in tiny
depressions in the wood's surface, such as pores or sanding scratches, stains
are great for highlighting the texture of the wood.
A dye uses a mixture of dissolved chemicals to achieve its color, and these
bond chemically with the wood fibers. Since the coloring takes place
on the molecular level, there is little or no highlighting of surface texture
or blotching of the wood grain like solid pigment particles do - whatever
the dye touches, it colors evenly. Dyes have much less tendency to
highlight scratches, pores, or end grain because the intensity of color is
controlled mainly by the concentration of the chemical solution, not by how
thick a coat of it is applied, although repeated coats can have the effect
of concentrating the dye on the wood, giving a slightly darker color.
Finally, dyes do not have a varnish base like stains, so a dye can
usually be un-done easily by bleaching it out, since there is no sealer
protecting the color.
These differences allow the finisher to achieve a great array of different
effects by using dyes and stains in combination. For example, if it is desirable
to finish curly mahogany in a medium-dark color while "popping" the grain,
a thinned black dye could be applied to increase the contrast of the curly
grain. After a light sanding, a golden amber dye would be applied to heighten
the "popping" effect, then a sealer. Finally, a dark brown glazing stain,
or gel stain, would be applied to achieve the final color and highlight
the pores of the mahogany.
Some coloring products use dyes and stains mixed together to achieve more
consistent results on different woods. Some topcoats even have dyes
and stains mixed into them, intended for "one-step stain and topcoat" finishing,
however after several coats of these products, the grain of the wood is often
obscured and few users are happy with the results. A better choice is to
use separate color and clearcoat.
Safety in the workshop is YOUR RESPONSIBILITY alone; I make no warranty as
to the safety of any technique or tool shown or described on this site.
Before beginning any project, you must understand woodshop safety,
know how to safely operate any machinery that is to be used in the project,
and understand the safe use and any potential safety hazards involved in
the use of all materials to be used in the project. See the
General Safety Notice and the
Chemical Safety Note for additional
General Characteristics: since pigment is composed of solid particles of
color ground to a fine powder, it is non-transparent (opaque), but also tends
to be lightfast (fade-resistant). Stains color by the action of pigment
being adsorbed onto the fine texture of the wood's surface, so they do a
great job of highlighting the wood's natural texture. On the other
hand, any "extra texture," such as sanding scratches, tearout, crushed wood,
or even end grain will tend to pick up more color, resulting in streaking
or blotching. An artificial lack of fine texture, the result of sealing
the wood (leftover varnish when stripping, or glue spots when building or
repairing furniture), will result in a "hole" in the stained color. Stains
tend not to penetrate into the wood, but rather sit on the surface. Also,
due to the varnish binder that "glues" the pigment to the wood's surface,
stains will often show lap marks if an area is stained and allowed to dry
too long before staining the adjacent area. Normally, careful planning
and efficient execution of the staining process can avoid lap marks, but
on extremely large and complex surfaces, it may be necessary to choose a
product that will not show lap marks. The varnish or oil binder used
in stains also means that the job cannot be "un-done" once the color is applied:
the binder glues the color to the wood and protects it from chemical bleaching,
so the only way to get the color off is to chemically strip off the binder
and scrub the color off the wood as best you can, or simply remove the surface
by sanding or scraping to reveal the unstained wood beneath.
See Water-Based Dye under Dyes, below.
Earth Pigment / Furniture Powders
Very fine powder, can be mixed into any liquid base; easy to use,
non-penetrating. Can be mixed with protective finishes (such as varnish).
Gel, pigment in a varnish and jellied petroleum base (somewhat similar to
napalm); easy to use, covers more evenly because it does not penetrate, bleed,
or even flow readily. Will show lap marks.
Gel-like liquid, pigment suspended in varnish; excellent for figuring, shading,
correcting sap streaks, and other glazing techniques. Glazing stain
is like a more liquid and transparent version of a gel stain. By
definition, glazing is applied over already sealed wood, so this type of
product is not meant to be used as a stain in the usual sense.
Liquid, earth pigment concentrated in an oil varnish; excellent for tinting
varnishes or mixing custom oil-base stains. Tends to dry slowly unless
catalyzed with Japan drier. Popular with old-time sign painters, because
the high-pigment formula holds sharp edge details without "feathering out."
The slower drying time of Japan color makes it ideal for projects where
lap marks might otherwise be difficult to avoid, however it also means that
the stain must be allowed to dry for a very long time before topcoating,
to avoid picking the color back up into the topcoat.
See NGR Dye under Dyes, below.
See Alcohol Dye under Dyes, below.
Water Based Stain
Liquid, pigment or pigment & dye suspended in an acrylic and water base;
brilliant, easy to mix colors; non-penetrating (or partially non-penetrating
if a dye is used), non-toxic, non-flammable. Will raise grain and will
show lap marks.
Water-Based Dye Stain
See Water-Based Dye under Dyes, below.
Liquid, pigment or pigment & dye suspended in varnish or oil; non-penetrating
(or partially non-penetrating if a dye is used). The most commonly
available type of stain, and tends cover unevenly more often than a gel stain,
but the thinner consistency spreads on and wipes off of complex surfaces
such as carvings more easily. Most wiping stains use a varnish binder,
which will show lap marks, but a few use linseed or tung oil as a base, which
dries slowly enough that lap marks do not normally occurr.
General Characteristics: dyes color the wood by the action of colored chemicals
bonding to the wood's fibers at the molecular level. Unlike stains,
dyes do not usually contain a varnish or oil binder, so the color can be
bleached out if needed, at least until it's covered by the varnish topcoat
or sealer. Because it's individual molecules, not pigment particles,
that supply the color, dyes produce totally transparent color, but they're
also more prone to fading when exposed to ultraviolet light from the sun
or from fluorescent lighting fixtures. Just like water gets the wood's
surface equally wet all over, dye tends to color the wood pretty evenly
everywhere, regardless of end grain, tearout, or sanding scratches, so blotching
is not much of a problem with dyes. (Was that a cheer I just heard?)
On the other hand, dyes tend to color the wood pretty evenly all over,
pores or no pores, so they don't usually do anything to hoghlight the texture
of porous woods like oak or mahogany. For that, I'll generally dye
the wood, apply a sealer, and finish the job with a glazing stain to bring
out the pore texture without the possibility of blotching (because the wood's
been sealed, only the pores are open to hold the glazing stain). After
a few coats of clear varnish or lacquer, I'll have a finish with a depth
of color you won't see on something that's been merely stained and varnished.
Alcohol Dye / Aniline Dye (alcohol base) / Spirit Stain
Alcohol soluble powder; penetrating, dries quickly, but tends more to show
lap marks. Does not raise wood grain the way water based dyes do.
See Water-Based Dye below.
NGR Dye / Stain (Non-Grain Raising)
Liquid, dissolved in methanol & petroleum distillate solution; does not
raise grain, lightfast.
Oil Dye / Stain
Oil soluble powder; penetrating, transparent, slow-drying, needs sealer coat
Penetrating Oil Stain
Liquid dissolved in mineral spirits; penetrates open-grained wood, moderately
lightfast, transparent, easy to apply & mix colors, bleeds, needs wash
Liquid, dissolved in varnish; highly transparent, lightfast, non-penetrating,
adds filler, color, and gloss in one operation.
Water-Based Dye / Dye Stain / Aniline Dye (water base)
Powdered, water soluble; penetrating, transparent colors, brilliant, compatible
with any finish, may be non-toxic, and will raise grain. Water-based
dyes are often called aniline dyes, although they no longer contain this
highly toxic class of chemicals. These dyes can be used to tint water
based finishes, and when applied directly to the wood, they tend to bleed
into water based top coats if they are not sealed in first. This can
produce problems by highlighting drips, sags, and lap marks; but if carefully
used, it can also have the effect of evening out the color absorption in
highly figured woods. Bleeding can be prevented by applying a shellac
sealer over the dye. Powdered dyes also come in alcohol soluble form
(see spirit stain), though the alcohol tends to 'wash out' the color a little.
N A T U R A L D Y E
& C H E M I C A L M O R D A N T S
A synthetic dye or the active coloring agent of madder root. Produces
"Turkish Red", crimson, orange, yellow, and brown, depending on the mordant.
An ancient organic dye from the borage family. Used in french polishing,
produces gray tones with alum, a range of reds with linseed oil.
Seeds from a Central American Tree. Produces oranges and golds with
dichromate, tin, or alum, oak brown with lye.
A popular dye from several species of South American redwood trees.
Produces vibrant reds, browns, and purples, depending on the mordant.
Dried tropical insects. Produces many shades of red; mixed with alum.
An extract of the heartwood of the Asian acacia tree. Produces various
lightfast shades of brown, from beige to chocolate.
A resin from any of various tropical plants, including a Malaysian palm and
an agave native to the Canary Islands. Produces bright, lightfast reds.
Often used to color violin varnish.
An extract from the heartwood of the American Mulberry tree. Orange
Yellow on its own, Yellows to greenish-yellows with alum.
A dye extracted from Indian indigo plants. Produces deep blue, yellow-white
An extract from Central American campeche hardwoods. produces lightfast
grays, browns, blacks, blues, and purples, depending on the mordant.
Extracted from the roots of the Eurasian madder plant. Produces reds,
blues browns, and yellows, depending on the mordant.
Always wear gloves designed to resist the chemical(s) being handled, and
wear safety goggles designed for protection from spattered chemicals (these
have covered vents). Chemical mordants should always be mixed in clean,
non-porous containers. Never mix two chemicals without prior knowledge
of any potential reactions between them. When mixing chemicals with
water, always add the chemical to the water, never the other way around.
It is strongly recommended to do further research into the nature
of a particular mordant prior to using or handling it.
Alum (Aluminum Sulphate)
White mineral salts, non toxic. Produces purplish and dark crimson
Ammonia NH4 (aq)
Usually in a 28% aqueous solution, highly toxic, used in fuming. Produces
dark violet browns with logwood dye, light yellow browns with brazilwood
dye, reacts with the tannin present in some species to darken or "age" the
wood. Anhydrous ammonia is very dangerous, so avoid it.
Copper Sulfate (Blue Vitriol) CuSO4
Blue crystals, highly toxic, used for preserving wood. Produces dark
gray and olive tones with logwood dye.
Ferrous Sulfate (Copperas) FeSO4
Crystals, highly toxic, reacts with tannin in wood. Produces steel
gray to bluish tones, ebony-like black with logwood dye or alum.
Hydrated Lime (Quicklime, Calcium Oxide) CaO
Crystals, toxic. Produces antique limed finish on hardwoods such as
cherry and walnut, must be neutralized with vinegar or other dilute acid.
Potassium Carbonate (Potash) K2CO3
Crystals, mildly toxic. Produces a range of greens with alum and fustic.
Potassium Dichromate K2Cr2O7
Crystals, orange in color, extremely toxic, reacts with tannin. Produces
deep reds to rich browns, combines well with aniline dyes.
Potassium Permanganate (Violet Potash) KMnO4
Crystals, mildly toxic, used for ebonizing. Turns wood with high tannin
content a purplish brown. Dyes skin brown on contact, won't wash off.
Sodium Hydroxide (Lye) NaOH
White powder, toxic, caustic, and hygroscopic, so keep it in a tightly closed
container. Easily obtained as a drain opener, darkens cherry and oak,
must be neutralized with vinegar or other dilute acid.
Stannous Chloride SnCl
White crystals, moderately toxic. Produces light red with brazilwood
dye, pink with alizarin, combines well with many dyes.
Tannic Acid C14H10O9
Yellow or brown powder, mildly toxic. Boosts the tannin content in
wood. Often used when fuming with ammonia or when ebonizing with an
iron acetate solution.
Time Life Books - The Art of Woodworking Series - Wood Finishing,
St. Remy Press, 1992
Webster's New World College Dictionary, Third Edition, Simon &
Schuster, Inc., 1997