One method of removing white water marks (rings) is to wipe over with a lightly alcohol-dampened cloth. Youll have more control if you fold the cloth into a pad, like a French-polish pad. You should only use enough alcohol to leave a trail of alcohol that looks like a comet’s tail when you wipe.
A wet drinking cup can leave a dark or ugly ring on your furniture. Here’s how to repair the damage.
Furniture with aged finishes can have watermarks. These marks, also called water rings when theyre round in shape, rarely occur in newly applied film-building finishes, even those such as shellac that have reputations for weak water resistance.
There are two types of watermarks: light and dark. Light marks are milky-white and are caused by moisture getting into the finish and creating voids that interfere with the finishs transparency. Dark marks, which are brownish or black, are caused by metal residue and water penetrating cracks in the finish.
Both are very easy to remove, but you will need to strip the finish before you can remove dark watermarks. Do not confuse heat damage with ink stains with darker watermarks.
Light WatermarksTo remove milky-white watermarks, you need either to consolidate the finish (eliminate the voids) to the point that the transparency is reestablished or cut the film back to below the damage. Success is not predictable, but in general, a white watermark is easier to remove in the following circumstances: 1) the finish is newer, 2) the shorter the time the watermark has been in the finish, and 3) the shallower the damage goes into the finish.
For lacquer finishes, spraying a light mist of blush eliminator (butyl Cellosolve) is very effective for removing light water damage. My friend removed his table from his car and placed it on the lawn. In a matter of minutes, I was able to remove the white marks using my magic aerosol.
Here are the best ways to remove milky-white watermarks, arranged in order from the least damaging (and generally least effective) to the potentially most damaging.
Apply an oily substance, such as furniture polish, petroleum jelly or mayonnaise, to the damaged area and allow the liquid or gel to remain overnight. The oil will often restore some of the transparency (by filling some of the microscopic voids) but seldom all of it.
To soften the finish and make it more stable, heat the finish with a blowdryer or heat gun.
If you heat the finish just right, this can restore some transparency. However, if it gets too hot, it may blister. Do not heat the finish more than it is comfortable to touch.
Dampen a cloth with denatured alcohol and wipe gently over the damaged area. You need to dampen the cloth enough that it doesn’t leave a trail of alcohol evaporating as you wipe. (You can practice by wiping across a more resistant surface such as polyurethane or plastic laminate.)
If you get the cloth too wet, the alcohol may soften the finish too much and dull the sheen or smear the finish. This is particularly true if you use shellac on furniture made before 1930s. However, this technique works best on shellac.
Use an aerosol blush eliminator to spray a light mist over the water damage. Butyl Cellosolve is the solvent that will dissolve lacquer, and restore transparency. Be very careful to avoid too wet a spray or it could damage the finish.
These aerosols can be purchased by professionals. These aerosols are available at professional distributors.
You can reduce the damage by using a mild abrasive, such as toothpaste or rottenstone (a fine abrasive powder that is available at most paint shops) mixed with oil. A light oil such as mineral oil can be used to lubricate fine #0000 steel wool. However, it will cause visible scratches on the surface. Steel wool should be used only as an emergency.
You should rub the area affected until you have removed all water damage. Be careful not to scratch the finish. Then, if the sheen is different from the surrounding area, even it by rubbing the entire surface with an abrasive that produces the sheen you want.
French polish over the damaged area using padding lacquer, another product sold to professionals. The lacquer-thinner solvent in the padding lacquer will soften the finish (the same as if it were wiped or sprayed on separately) and often clear up the damage. It may be necessary to continue polishing the entire surface to get an even sheen.
This technique works fairly well on surfaces in good condition, but it is risky on crazed or deteriorated surfaces. If the watermark doesnt come out entirely with your initial application, you will seal in the remaining milky whiteness and make removing it more difficult.
If you have no experience removing milky-white watermarks, I recommend you try wiping with an alcohol-dampened cloth or rubbing with an abrasive. These techniques are both effective and less likely to cause serious damage.
Dark Watermarks
Dark water stains can be removed by first removing the finish. Next, dissolve the oxalic acid crystals in hot water to make a saturated solution.
Oxalic acid wood bleach is the best and most effective way to get rid of dark watermarks. You can purchase this chemical in crystal form from pharmacies as well as at most paint and hardware shops. Dont confuse this bleach with household bleach, which removes dye, or with two-part bleach, which takes the natural color out of the wood.
You can dissolve some oxalic acid crystals in a mixture of one ounce to one quarter of a quart of warm or hot water.
Glass jars make a great container. However, you should leave enough space at the top to allow gases to collect if the solution is stored in a glass jar. Metal containers rust quickly so don’t use them.
To keep the color consistent, apply a thin coat of the solution to the entire surface. If you are working on mahogany or cherry, which usually darken as they age, the oxalic acid may lighten the wood back to its original color.
Apply the oxalic acid solution to the entire surface. The dark marks will begin to fade immediately, though it will take a little longer for them to disappear entirely.
After the oxalic acids has dried, wash the wood with a hose, sponge or cloth. Dont brush the crystals into the air because they will cause you to choke if you breathe them in.
Usually, one application will remove the black marks, but you can always try a second if the first doesnt work. After the black is removed, there will be a slight tan. It can be removed easily with a light sanding.
Attention: Oxalic Acid is toxic and can cause severe skin and respiratory problems. Wear gloves and goggles when using it, and dont generate airborne dust.
The crystals will return to the wood after it dries. Wash them off with a hose or wet rag or sponge. Never brush the crystals off the surface because they are toxic to breathe.
Oil Finishes
Dark watermarks occur easily in oil finishes because theyre too thin to be effective against water penetration. However, milky-white watermarks can be found very rarely. The lighter watermarks you sometimes see in oil finishes are almost always caused by random light reflection from raised grain telegraphing through the thin oil.
To repair light, raised-grain watermarks in oil finishes, level the raised grain with sandpaper or steel wool and apply more oil finish. Abrade the damaged area as little as possible to avoid lightening the color of the wood. PWM
