by Carl Duguay
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.
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).
Bombe Box by Charles Neil
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. The 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.
Ban the Blotches
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. 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.
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.
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.
Finishing Tip by Bob Flexner
To achieve an even coloring with darker colored woods, it’s always best to use only heartwood to begin with. But this isn’t always possible. So you may want to “equalize” the coloring of the sapwood and heartwood.
But it’s usually better to equalize the sapwood to the color of the heartwood.One method is to bleach the wood using two-part bleach (sodium hydroxide and hydrogen peroxide). This will remove the coloring from the heartwood, so you can then stain the wood back to the color you want.
The easier way to do this, if you intend to stain the wood dark, is to use a dark dye stain as shownin theaccompanying picture. Light colored dye stains don’t work as well,manned stains that contain binders, such as oil, water-based and lacquer stains, work even less well.
Though more difficult, the best way to equalize the coloring is to spray a dye stain just on the sapwood, asshown on the middle stripe in the second accompanying picture. You can then follow with a binder stain if you want to further equalize the coloring, as shown on the stripe second from the right. Finally, apply the finish, which will produce the true coloring.
The way you prepare the wood for finishing, whether by sanding as most do, or by scraping or planing as some do, has no affect on the way the wood will look with the finish applied. Different finishes add more or less color to the wood, but if you aren’t staining the wood, the way you prepare it has no impact on the appearance under any single finish.
Nor does the grit to which you sand the wood make any difference for the appearance with the finish applied. You can sand to 120 grit or to 600 grit and you won’t see any difference after you have applied the finish.
This is somewhat counter-intuitive because the wood is glossier (shinier) when scraped, planed or sanded to a finer grit.
The way you prepare the wood does make a difference if you apply a stain, however. You should prepare all the wood exactly the same, meaning for most of us, sanding to the same final grit.
Finishing is hard enough even without the mislabeling that is so prevalent on the part of many manufacturers. The mislabeling makes it difficult for us to know what we are buying and using.
The accompanying picture shows dried puddles of two commonly available products both labeled “tung oil.” These two products could hardly be more different.
The tung oil on the left is real tung oil, the oil produced from pressing the nuts from tung trees, which are native to China. A puddle of the oil dries wrinkled, and it never really hardens. You can always scrape it off with your fingernail. As a result, you need to wipe off all the excess after applying each coat or the resulting finish won’t be functional. With real tung oil you can’t get a build.
The “tung oil” on the right is actually varnish, which has been thinned with mineral spirits (paint thinner) so it is easy to wipe on the wood. But it dries hard, so it can be left thick on the wood and can be built up with several coats for better resistance against water penetration.
You might think: well, maybe the finish on the right was made with tung oil, so that’s the reason the manufacturer labels it “tung oil.” But this isn’t the case. It’s made with modified soybean (soya) oil. You can tell this (even if the manufacturer doesn’t volunteer the information) by the lack of yellowing in the finish as it ages.
Varnishes made with linseed oil or tung oil yellow significantly, just as the real tung oil on the left has. The reason modified soybean oil is used in most varnishes (including polyurethane varnishes) is because it yellows very little. It is more “lightfast.”
When brushing a finish onto a large horizontal surface such as a tabletop, it’s most efficient to lift a brush load of the finish (the bristles dipped about halfway into the finish) out of the container and plop it down at the center of the area you want to brush. Then stretch out that puddle of finish from end to end working in the direction of the grain.
Work fast without dragging the brush over the edge at each end, which would result in runs down the side. You can accomplish this by using airplane-like landings just in from each edge as you brush back and forth.
When you have lined up the brush strokes end to end at least one brush width wide, plop down another brush load about an inch from the previous strokes and stretch it out end to end while working it back into the existing finish. Continue with this procedure until you have covered the surface all the way across.
To avoid drips where you don’t want them, hold the container of finish in your other hand near where you deposit the brush load of finish.
A key factor in choosing a finish for an enclosed space such as a drawer, cabinet interior, humidor or a small room such as a wine or liquor cellar is residual odor. All types of varnishes and lacquers outgas smelly solvents for many days or weeks depending on the thickness applied, the temperature, and the air movement. If you can’t allow that much time, you need to choose another finish.
The two that will leave the least residual odor are shellac and water-based finish. Both contain solvents that evaporate fairly slowly (alcohol in shellac and glycol ether in water-based finish), but they leave almost no odor.
It’s still best to allow adequate time for the finish to dry completely. A way to test is to press your nose up against the finish and take a whiff. If there’s absolutely no odor, the finish is dry.
“I prefer to spray my shellac. Spraying shellac results in an even smoother finish which greatly reduces the amount of sanding during finish work.”
Rodney Dangerfield’s famous comedic catchphrase was, “I don’t get no respect.” In the world of furniture finishes, shellac gets no respect. That lack of respect is unwarranted. In fact, shellac is my “go to” finish on fine furniture. It should be yours as well.
The lack of respect for shellac may be due to the fact that it, a natural resin, is made from a bug’s secretions – not bug droppings, as some think. A lac insect, about the size of an apple seed, ingests tree sap which undergoes a transformation before being secreted as a shell-like shield that covers the bugs. The secretion also sticks to tree twigs. If it is scraped from the twigs, the result is known as “sticklac”, but if it is knocked free from the twigs using wooden mallets, the shellac is known as “grainlac.” Both are sent for additional processing.
As it is being processed, the story of shellac does not get any richer. Originally, shellac was ground in mills, sifted through screens then soaked in large containers of water. At some point a worker jumped into the containers and, with his feet, rubbed the shellac against rough-textured sidewalls to break open the seeds and release the bug remains. The concoction was then rinsed and spread onto concrete floors to dry. While this was how it all happen in the past, today the process is handled by machines.
Further disrespect for shellac could be because we do not realize its widespread use, most of which are not furniture-finish based. Shellac was and is used as sizing for men’s hats, printing ink, candy coating and adhesives. The closest we come to furniture finish is floor wax and shoe polish. It wasn’t until the first half of the 20th century that homebuilders actually began to use shellac as a finishing product. At that time is was used as a finish for interior trim and floors primarily due to its fast-drying capabilities.
The finish we see on shellacked woodwork in older homes is dark. This is not necessarily a result of the shellac, which is UV-resistant and does not change in color over time, it’s more a result of finish choices at the time. While early shellac was less refined (adding to the darker coloration) homeowners looked for a deep rich color so contractors tinted the shellac.
Today, many woodworkers find fault with shellac because of unused shellac that has been mixed degrades over time – that is another reason for the lack of respect. Degradation effects drying times and the film finish stays softer and is more easily scratched. Eventually, as the degradation continues, if you use outdated product, you end up with a gummy mess with which to deal. Experience taught me this lesson, so I watch my expiration dates closely. It’s best to keep shellac fresh.
Shellac is sold pre-mixed in cans or is sold in flakes that you mix, when needed, with alcohol. Since shellac has a shelf-life, it’s best if you know when your finish was mixed. Obtaining the date of mixture is easy when you mix your own shellac, but because you need time for the flakes to dissolve in alcohol, some woodworkers balk at mixing their own.
Pre-mixed shellac, in the United States, is sold by Zinsser. Zinsser shellac has a company-reported shelf-life of three years from the date of manufacture. The company provides codes printed on the can lid that indicate the date of mixture, but you have to decipher that code.
A typical code found on a can lid might be S0720BD. The first number after the letter is the year the shellac was mixed. In this case, you see 0 which indicates 2010. If the number was 1, it would represent 2011, and 2 would indicate 2012. The first number after the year indicator is the month of mixture. In the example, 7 indicates the month of July. The numbers 1 through 9 stand for January through September, 0 indicates October while N is for November and D for December. If you need more in-depth information, the two numbers that follow the month indicator tell you the exact date of manufacture.
Another reason that woodworkers lack respect for shellac stems from the many myths that surround this finish. Myths such as, shellac is difficult to use, lacks water resistance and is incompatible with other finishes. These beliefs are simply not true.
Shellac is not only simple to use, it is easy to repair. Once mixed, either from flakes or directly from a can, shellac can be brushed on, ragged on or sprayed onto your project. If you brush shellac, use a good-quality brush. A good brush carries more shellac to your project and that allows you a better flow of the shellac for a smoother finish. This idea is the same for most any brush-applied product. Also, fast drying times allow for more coats to be applied daily (a faster finish process) and keeps shop dust out of your project.
I prefer to spray my shellac. Spraying shellac results in an even smoother finish which greatly reduces the amount of sanding during finish work.
Lack of water resistance has long been a stab at shellac. Hhowever, fresh shellac is remarkably water resistant. Shellac will develop white rings from glass condensation, but only after hours of neglect. And the truth is that much of the necessary water protection should come from a protective coat of wax.
Lack of compatibility is my favorite shellac myth. In nearly 20 years of working with shellac – from flake and store-purchased – I ran into a problem once when I added a layer of lacquer over a coat of shellac.
Compatibility is no problem at all if you’re about to add shellac over an earlier coating. In fact, I have yet to see shellac not adhere to any base coat, especially if you scratch the earlier layer to prepare for your shellac. Simply put, shellac covers all.
Working the other direction or when you apply other topcoats over shellac, it is often noted that you should not apply polyurethane over shellac. My personal opinion is that you should not use polyurethane, at all. But with that quick step on and off of my soapbox, I will say that even the company recommends that you do not use a polyurethane over shellac, but many woodworkers do this on a daily basis without any concerns. It is, however, OK to use an oil-based urethane over shellac.
Other than polyurethane, I have not heard nor experienced any problems with adhesion to shellac except for the lacquer mentioned above. To clarify that situation, I had used amber shellac to warm a cherry finish – one of my favorite finishes for cherry and walnut – when I sprayed on my first coat of dull-rubbed effect lacquer, there were two areas the size of a half-dollar that peeled off. I can only surmised that my shellac or my lacquer were close to outdated, or that those two areas contain a higher concentration of wax. A simple fix would have to apply a coating of dewaxed shellac prior to moving to my lacquer.
Just as Mr. Dangerfield was a much beloved comedian/actor who had a lengthy career, shellac, once hailed as the best finish for fine furniture, has been around for a long time. It has stood the test of time. If not for the furniture factories who want to switch to a “new and improved” product while dumping what was considered an “old-fashioned” finish, furniture makers today would not have to rediscover this great product. If you have not worked with shellac, do yourself a favor and try it. You will be delighted.
It’s generally better to use a dedicated paste wood filler (pore filler) to fill pores than the finish itself, or sanding sealer, because finishes continue shrinking. This will cause the pores to noticeably open up a little after a few weeks or months.
But you can use the finish for filling, especially if it’s water-based because water-based finishes sand fairly easily and don’t shrink as much as varnish and lacquer. Apply several coats, sand them back using a flat block to back your sandpaper, and continue doing this until the pores are filled.
Varnish and lacquer are more difficult to sand because they tend to gum up the sandpaper. Here’s a trick to make the sanding easier and make it less likely that you’ll sand through.
First apply a coat of the finish, varnish or lacquer, whichever you are using. Follow with several coats of varnish sanding sealer or lacquer sanding sealer. Sanding sealers sand much easier than the finish itself, which is the reason they are sometimes used for the first coat.
Then sand the sanding sealer, as shown in the accompanying picture, until you feel the resistance of the coat of finish at the bottom, which is the varnish or lacquer. Stop when you feel this, clean off the sanding dust and decide if you need to apply and sand more coats of sanding sealer to fill the pores level.
Finally, apply several coats of varnish or lacquer to finish up.
Products sold as wood conditioner are washcoats usually made from varnish, though I have seen at least one that is an oil/varnish blend. A washcoat is a finish thinned to five-to-ten percent solids with the appropriate thinner. (Finishes are generally supplied with 20-to-30 percent solids.) In industry, the finish used is usually lacquer thinned with lacquer thinner.
Wood conditioners can be fairly effective on softwoods like the pine shown in the accompanying picture. They aren’t as effective on hardwoods such as cherry.
The purpose of the thinned-finish conditioner is to partially seal the wood, which means to partially stop up the pores so the stain, which can cause a blotchy appearance, can’t penetrate as deeply in those areas that will get darker.
To use a wood conditioner effectively, it’s important to understand that the directions supplied by almost all brands won’t produce good results. These directions say to apply the stain within two hours, which is before a varnish or oil/varnish blend has time to dry. So the stain mixes with the uncured wood conditioner and still blotches.
To use a wood conditioner effectively you have to give it time to completely dry so the stain can’t penetrate. With lacquer this is 30 minutes or so. But with varnish and oil/varnish blend this is overnight, or at least 6 to 8 hours.
To significantly reduce blotching, apply the wood conditioner wet to the surface of the wood and let it completely dry. Then apply the stain and wipe off the excess. But notice from the example that with less stain penetration, the resulting color is also lighter.
I have no idea why manufacturers give directions that don’t work. The only explanation I can think of is that they believe you want to totally complete a project on a Saturday afternoon, and waiting overnight for the wood conditioner to dry won’t accomplish this.
As long as you are using a spray gun for application and lacquer for your finish, you don’t have to let an oil-based glaze dry overnight before applying the finish. You can do it fairly quickly, without problems.
The trick is to mist some thinned lacquer onto the glaze after the thinner in the glaze has evaporated (the glaze dulls) but before the oil or varnish binder begins oxidizing and becomes tacky. Unless the glaze is thick, in which case this trick might not work, the lacquer incorporates the uncured glaze and bonds to the coat underneath.
After the mist coat has dried, which is within 10 minutes or so, continue with your finish coats.
This same trick should also work with oil-based stains that have been wiped off. Give the thinner enough time to evaporate (or the lacquer may come out of solution and turn white), then mist on the thinned lacquer and let it dry. It would be a good idea to experiment on scrap wood first to be sure you have the timing right.