Water causes wood to swell, so most people think that wetting one side and not the other will cause the wetted side to bow – that is, increase in width so the center is higher than the edges.
If the wood is thin enough, this will be the case initially. But the overall swelling or shrinking after many wettings and dryings out, no matter the thickness of the wood, will be the opposite. The wetted side will shrink and the wood, or boards, will cup. The four accompanying pictures show examples of this. With a little thought, you will most likely come up with examples from your own experience.
The explanation is a phenomenon called “compression set” or “compression shrinkage.” When one side of wood is wetted the wood cells want to swell. If the thickness of the wood prevents them from doing this, they compress from cylinder shapes to oval shapes, and they don’t return fully to their cylinder shapes when the wood dries out.
The compressions are cumulative. So after many wettings and drying outs, the result is shrinkage. Eventually, the wood can’t shrink enough on the wetted side, so it splits. On a deck, for example, this shows up first as small “checks,” or splits all across each board.
None of this has anything to do with heartwood or sapwood up, or planesawn vs. quartersawn. The continuously wetted side will be the side that shrinks.
This is the reason wood exposed to water on one side should be protected with a finish in good shape and thick enough so water can’t get through. It’s the reason deck stains and water repellants are not very effective, and it’s the reason the message of the Antiques Roadshow, “Don’t Refinish,” has been so destructive to our furniture heritage.
Watermarks can happen in all finishes after they have aged and become somewhat porous. The marks appear light gray to white and are almost always very superficial – that is, right at the surface of the finish.
So one way to remove them that almost always works well is to abrade off the very top surface of the finish with fine steel wool or abrasive pad. Usually, the discoloration will be removed with very little effort, as shown in the two accompanying pictures.
The downside of removing watermarks in this manner is that you may change the sheen of the finish, making it flatter or glossier, and there’s no easy way to disguise this.
The first choice would be to blend the sheen of the rubbed area in with the sheen of the surrounding area. Do this by choosing a grit steel wool or abrasive pad that does this well. You can try several times with different grits to try to achieve a match. You can also use different pressures to “feather in” the rubbed sheen.
No matter how close you get however, a rubbed sheen never looks exactly the same as a sheen created by just the finish because a rubbed sheen is composed of scratches.
To get the entire surface, almost always a tabletop, uniform, you’ll need to rub the entire surface with the same grit abrasive. You could also apply another coat of finish on top. The least risky, if you don’t know the finish you’re working on, would be shellac, or wiping varnish padded on.
You might choose a finish for its durability, drying speed, ease of use or cost, but you might also choose for the color it imparts to the wood.
The accompanying picture shows unfinished oak at the top left, then seven common finishes and their color. If you haven’t done this comparison side by side, you may be surprised at the amount of difference.
On top row from the left: unfinished, clear paste wax, water-based finish and nitrocellulose lacquer.
On bottom row from the left: clear/blonde shellac, amber/orange shellac, polyurethane varnish and boiled linseed oil.
In practice, wax would be an unusual choice because it offers almost no moisture resistance. Linseed and other oils offer only a little more because they can’t be built to a moisture-resistant thickness. But they are easy to apply, so they work fairly well on objects without tabletops.
Of the remaining film-building finishes (they dry hard, so they can be built to several layers) water-based finish and amber/orange shellac are the most unique. Water-based finish imparts no color; it just darkens the wood a little. Amber/orange shellac imparts a lot of orange color.
You may choose either of these finishes just for the color.
It’s common to be instructed to apply a finish in the direction of the grain, called “with the grain.” Doing this is usually best when brushing a finish, but it’s rarely necessary when wiping or spraying a finish.
Brushing with the grain is best because the grain will help disguise the brush marks, the ridges and troughs caused by the movement of the bristles along or across the surface. If you brush across the grain, the brush marks will stand out in contrast to the grain of the wood.
There are exceptions, however. These include solid or veneer with their grain running in different directions – for example, breadboard, sunburst, parquetry, etc. If the grain of the boards or veneer runs in the same direction, it’s always best to brush with the grain.
Spraying, and wiping on and wiping off, are different. With spraying, as long as you build the finish enough so there aren’t dry streaks or areas with too little finish, it doesn’t make any difference in which direction you spray. For example, you might find it easier to spray horizontally on installed vertical panels rather than turn the air nozzle 90 degrees and spraying up and down.
With wiping, as long as you wipe off all the excess, it doesn’t matter in which direction you wipe on the stain or finish. The only consideration is in wiping off. If there is any chance that you may leave streaks, because you don’t get all the excess wiped off, you should wipe off with the grain.
There are risks to spraying any type of solvent lacquer over any existing, and older, paint or finish. The problem is the lacquer thinner in the lacquer. A wet application can cause many paints and finishes to wrinkle or blister, even an old coat of lacquer itself.
The two easiest ways to avoid problems are to spray several light (almost dust) coats of lacquer to get a bit of a build before applying wet coats, or to apply a coat of shellac before spraying the lacquer.
Both methods will create a barrier to keep the existing coating from being excessively wetted by the lacquer. But a fully wet coat of lacquer, especially if it has been retarded (lacquer retarder added to slow the drying), can still dissolve through and cause a problem. So observe closely what is happening.
Of course, brushing a brushing lacquer, which, by definition, has been retarded so it dries slowly enough to brush, is very risky and should probably not be tried.
Many people are confused about whether or not to refinish old furniture whose finish is in bad shape. They don’t really like living with the furniture, but they’ve heard (usually directly or indirectly from the Antiques Roadshow) that refinishing destroys value, and they surely don’t want to do that.
A finish serves two purposes. It protects the wood from contact with liquids, and it makes the wood look better, usually richer and deeper. The finish protects and decorates.
Clearly the finish in the accompanying picture does neither. In almost all cases it should be removed and replaced with a new finish that does both. It should be stripped and refinished.
Not doing so will probably mean the disappearance of the furniture. Well-built furniture outlasts people, the reason we have antique furniture. Though you, or whoever owns the furniture now, may be willing to live with the deteriorated finish, what happens to the furniture when it gets passed on? How many generations will treasure the deterioration, which will only become worse?
Not likely very many. This is the real shame of the message of the Antiques Roadshow, which typically runs as follows: This is a really unique piece of furniture. In its present refinished condition it’s worth about $5000. But had it not been refinished, it would be worth $60,000!
Groan. Why did someone refinish it?
Well, they refinished it because it needed to be, or it would have ceased to be useful. If they hadn’t refinished it, it probably would have disappeared into some landfill or fireplace and been worth nothing today. The current owner should be thankful someone cared enough to refinish the furniture, so they now have it to enjoy – or the $5000 if they choose to sell it.
There are exceptions, of course, but they are very rare. The appraisers on the Antiques Roadshow trade in these rare pieces, which probably accounts for their destructive message to the vast TV audience, very few of whom will ever come in contact with such rarity except in a museum.
The exceptions are usually very old, of very high quality, and were made by a craftsman who can be identified. Sometimes, an exception can be made for lower-quality furniture that was owned by an important historical figure, but you have to be wary of this sort of claim. I have had three separate pieces of furniture show up at my shop in Norman, Oklahoma that supposedly came from Paul Revere’s home, that little tiny house in Boston! He probably had only three pieces total, and all of them made it to Norman!
Of course, none of these three were anywhere near old enough to have been owned by Paul Revere.
Concerning value, unless the furniture is really unique, it will increase in value and survive with a beautiful, protective and decorative newly applied finish. It won’t lose value.
Naphtha, commonly sold as “V M & P Naphtha,” is better than mineral spirits (paint thinner) for cleaning oily and waxy surfaces, including crayon marks.
Naphtha is a stronger solvent than mineral spirits but not so strong that it damages any finish other than wax as long as you don’t soak the surface. Naphtha also evaporates much more rapidly, which I find to be a more user-friendly quality.
The downside of naphtha, compared with mineral spirits, is that it has a stronger odor. So it’s wise to arrange some air movement to remove the smell from the room or shop.
Each year, John Darroch, President and CEO of Apollo Sprayers and TheFinishingStore.com, judges the awards for the Excellence in Finishing at the prestigious Design in Wood (or @designinwood) show at the San Diego County Fair. Winners receive gift certificates from TheFinishingStore.com
This combined competition and exhibit is a collaboration between the San Diego Fine Woodworkers Association and the San Diego County Fair. Woodworkers from all over the world compete for honors in the largest show of its kind anywhere (according to Fine Woodworking magazine). Exquisite furniture, musical instruments, carvings, clocks, children’s toys and more — many museum quality — are included. Many pieces are for sale directly from the crafter.
This year, as always, the standards were extremely high. David Marr’s “Art Nouveau/Deco Vanity” won First Place in Finishing and was also awarded Best in Show.
Speaking to David Marr after his win, he acknowledged spending many hours, perhaps 450-500, to perfect the piece, in between other woodworking jobs. He’s been a professional woodworker for more than 20 years. He took as his initial inspiration the work of Emil Gallé, who designed furniture in the art nouveau period, and then put his own spin on it.
Woods used by David Marr were were olive, macassar ebony, pomelle sapele and the inlay was Honduran mahogany.
The whole piece is veneered, except for the inlay on the top. On top David used conversion varnish and the rest was sprayed with nitrocellulose lacquer. Interestingly, he used an Apollo Sprayer. Some years ago he won an Apollo Spray Gun in the Design in Wood competition and bought himself an Apollo 3-stage Turbine.
David Marr’s advice on how to produce a prize piece: “have a lot of patience.” He took his time since it was a really complicated piece where every joint is curved. It was difficult to build but he was determined to push his skill level further. As you can see, it paid off.
Second prize in Finishing went to Thomas Stockton, for his “Morning Glory Cabinet.” He’s been a woodworker doing custom work for 23 years and last year won the Master Woodworker’s Trophy.
Stockton was inspired by his love of morning glories and looked at lots of pictures of them before starting work. The wood is curly maple with the morning glories inlaid.
After he made the doors, he routed a cavity for each visual element, cutting the flowers with a jeweler’s saw, and then gluing them in with superglue. Next he sanded the inlay flush with the rest of the piece and sprayed with 8 or 9 coats of waterbased lacquer. The whole process took him approximately 200 hours.
His tip was to step away if you reach a problem. Go and think about it and come back later when you have a solution. He worked on this project in between other jobs for over a year.
Third place winner Donald Van Winkle was the exception in that this was the first time he’d entered Design in Wood. His “Chinese Display Unit” was inspired by an item he saw in China. A retired aerospace engineer, he took up woodworking in 1998 and took classes at Ceretos College in Norwalk, CA.
Van Winkle took 2-3 months just designing and researching the project. There are 7 types of traditional Chinese joints and he studied how to apply the appropriate joint in the appropriate place.
The wood frame is walnut and the shelves are made of MDF with olive ash burl veneer. The main feature was the unique joinery. In total the piece has 190 mortices. He constructed the piece at Ceretos College where they had a morticer that was essential to the project.
The finish was multiple coats of oil varnish applied and rubbed. He added a coat of colored wax on the walnut and clear wax on the shelves.
In all, the project took 650 hours. Donald Van Winkle, like all the winning finishers in this article counsels patience. His tip is “You have to be patient, and a little bit nuts.”
If you qualify, consider making a piece to enter in a show!
Glue seepage, or glue on your fingers that’s transferred to the wood, blocks stain penetration. This usually results in a lighter area. The same can happen with wood putty because it doesn’t accept color the same as wood does. In both cases, you have a lighter area or spot that you want to color in to match the surrounding wood.
Here’s how to do it.
As shown in the accompanying picture, the better method is usually to first seal the wood, then paint in the grain. Connect the grain lines on either side of the lighter area. When this has dried, apply a washcoat (a highly thinned coat of finish) to seal in what your have done, then color in the areas between the grain lines.
When you’re happy with the result (which is rarely an exact match), apply the topcoats.
For the coloring medium, ideally you want to use something that can be removed without disturbing the color underneath if you should want to begin again. The best medium is usually shellac because it can be removed by wiping with denatured alcohol. It won’t lift an oil stain. But it could lighten a water-based stain, so wipe very lightly.
Shellac also dries rapidly, so all steps can be accomplished in a short time.
Universal color pigment, the same as the paint store uses to tint latex paint, can be used with the shellac.
For the washcoats, aerosol sprays are widely available and work well.
Instead of shellac you could use thinned varnish and oil- or Japan-color pigments, but the drying time will be extended to a day or more.
Shellac is available in two forms: as a liquid in cans you buy at paint stores and home centers, and as flakes you buy from woodworking suppliers. The advantage of dissolving flakes (in denatured alcohol) is to ensure the shellac you use is fresh. The fresher the dissolved shellac the quicker it hardens and the more water-resistant the dried finish.
Unfortunately, the sole remaining supplier of already-dissolved shellac no longer supplies a date of manufacture, so you have no idea how long the can has sat on a shelf or been stored in a box somewhere. When finishing important surfaces, it’s best to dissolve your own flakes.
When you do this, be sure to stir fairly often, at least once an hour. Otherwise the flakes will soften and stick together at the bottom of the container. They will form a lump that will be very difficult to break up.
Though this tip may sound silly and obvious, I know from my own experience that it’s not. The first time I dissolved shellac flakes, I simply combined them with the alcohol and left the jar alone. Next day I realized what I should have done.
To make the dissolving go faster, you can reduce the flakes to powder (for example, in a blender) or place the container in hot water. With both methods you still need to stir, however, until the shellac has dissolved.