While there are some woodworkers who might cringe at the thought of staining wood, there are good reasons why you might want to do so. Some lighter colored woods, such as poplar, alder, beech, and birch do tend to look somewhat bland, and can benefit from a dash of color. Who hasn't bought a load of wood, only to find, after milling, a disappointing variation in the color - staining can even out the tone of the wood. When building new furniture or cabinetry to match existing pieces, staining might be the only way to blend the two. And, with the price of some exotic woods, such as ebony, reaching stratospheric levels, staining a wood to mimic the look of another species might not seem like such a bad idea. Or, you might simply want to make a really bold design statement. Whatever the reason, enhancing, and even completely altering, the color of wood is a valid, and indeed time honored woodworking tradition.
Bombe Box by Charles Neil
In a nutshell, a stain is a colorant that's dissolved in some kind of solvent (aka 'carrier'). The two most common types of colorants are pigments (which cover the wood), and dyes (which penetrate the wood). Some manufacturers combine both pigments and dyes into a single blended stain. The solvent can be alcohol, a petroleum distillate (such as mineral spirits, kerosene, and naphtha), and even the actual finish. A binder is added to pigment stains to help the colorant attach itself to the wood - typically the binder is a resin (acrylic, vinyl, alkyd and the like).
Pigments are fine insoluble particles of inert chemical compounds that can be natural (like iron oxides) or synthetic. Because pigment particles are heavier than the binder, they settle to the bottom of a can – which is why you have to stir these stains before using them. That big glob at the bottom of the can is a sure indicator that the can contains a pigment stain.
Pigment particles lodge in the pores and scratches on a wood surface, exaggerating grain differences. A pigment stain on open porous woods like oak tends to color the early wood more darkly than the denser latewood. However, on closer grained wood like maple, the stain would be much less pronounced because those pores are so small.
While pigments remain closer to the surface of the wood, dyes are absorbed into the fibrous structure of wood, which means the wood will be much more evenly colored. Dyes can be either natural or synthetic. Like pigments they require a solvent, but they don't use a binder. This is because dye particles, which are about 1/1000th the size of pigment particles, are fully dissolved in the solvent, while pigment particles are suspended in the solvent. Because dye particles are dispersed uniformly throughout the stain they don't have to be stirred. Like pigments, dyes can be dissolved in water, alcohol, petroleum distillates like naphtha, and in glycol ethers - in which case they're generally referred to as non-grain raising (NGR) dyes.
While natural dyes are prone to fading, modern synthetic dyes are quite fade resistant (when used indoors). The nice thing about dyes is that you can apply one color directly on top another color. You can purchase dyes either as powders that you dissolve in a solvent (water, alcohol, oil) or pre-mixed in a solvent.
Sometimes you'll read about people using various chemicals to color wood - potassium dichromate, ammonium hydroxide, sodium hydroxide, along with a range of other suspicious sounding names. Most of these chemicals are both poisonous and caustic, so you should really avoid them. There are so many stain colors available today that you'll certainly find the right one for your project without compromising your health.
Staining wood isn't difficult, just a bit messy sometimes. You can apply most stains with a brush or rag. It's important to note that different woods take stain differently. In fact, even one species of wood will take a stain differently depending on such factors as how the board was cut, the wood grain, and the relative density of the wood. Woods like pine, poplar, alder, and birch are notorious for blotching. For blotch prone wood I apply a thinned coat of shellac before I apply the stain. I also apply shellac on the end grain, which has a tendency to absorb stain like a sponge and darken much more than the surface.
Proper sanding of both solid wood and plywood is a key to achieving optimal results when staining. Make sure that you do a final sanding by hand, in the direction of the grain. Shine a light across the surface of the wood at a 45º angle - it will help you see any imperfections that need attending to. Also sanding the end grain smoother burnishes the pores and reduces their ability to absorb stain. It’s important to remove excess glue completely, particularly around joints.
It's a good idea to do a trial run on scrap pieces before you begin staining your project. You can experiment by diluting the stain with its solvent (check the label on the can) or laying on two or three coats of stain (allowing each coat to dry in between, of course). You really want to stir the contents of the can thoroughly before applying the stain. It's important that all the pigment is dispersed in the liquid as opposed to sitting on the bottom of the can. Generally, if a wood is very hard and dense, you should sand to a coarser grit than if the wood is soft and porous. If you sand maple to 220 grit it will absorb very little stain; better to sand the maple to 150 grit. However with oak I tend to sand to a higher grit, often 320.
For important projects I always buy ‘architectural’ or ‘cabinet’ grade plywood. Typically the face veneer on the good side will be one continuous sheet. Building supply stores typically carry a lower grade of plywood. Often, the face veneer is made up of multiple parallel bands of veneer joined together and running the length of the sheet.
Ban the BlotchesThe bands may not be matched, and more often than not there are even gaps along the glue lines. When stain is applied, the glue lines will likely absorb stain differently than the veneer.
Some woods, such as pine, cherry, and birch, are blotch prone - they absorb stain unevenly. For these I use a gel stain. These thicker stains don’t penetrate wood grain as much as thinner liquid (oil or water based) stains. A second option is to apply a wood conditioner (aka washcoat) before staining. The wood conditioner will help the wood absorb the stain more evenly. You can buy an off-the-shelf conditioner, or make your own by diluting your finish with the appropriate solvent in a ratio of 9 parts solvent to 1 part finish. Remember to allow the conditioner to thoroughly dry before applying the stain.
Lay it On
You can apply stains with a paint brush, foam brush, by rag (my preferred method), or spray. Liquid stains, particularly water based stains, dry fairly quickly, so on large surfaces you want to maintain a wet edge, to avoid lap marks.
Don’t take my word for it - you really need to try several different stains to find the one that suits your needs. Most are available in half-pint sizes for a few dollars a can. Once you’ve latched onto a stain that you like, experiment with it on the woods that you typically build with. Try different finishes on top of the stain as well.If they do occur lay on a second coat of stain after the first one has dried. On any project that will likely be exposed to direct sunlight, use a pigment stain – it’s much more lightfast. For projects that require vibrant, bright colors, or where you need to match an existing stain as closely as possible, use dyes. Any stain will result in a darker color if you leave it on longer, or if you re-apply it after the initial stain coat has dried.
You wouldn’t expect to cut perfect dovetails the first time you try, so you shouldn’t expect to get perfect staining results without some practice. But you will be surprised just how easy it is once you’ve invested a little time in honing your staining skills.