How To Fix Water Damage On Wood

Posted August 18, 2021

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Work miracles on wood with oxalic acid.

Watering a potted institute can exist disastrous if the plant lives on meridian of something made out of wood. Nosotros've all seen the white spots and black rings that can result when water seeps through the pot. And if you've e'er tried to sand out these marks, yous know it's a tough task that tin can leave telltale depressions on the surface. Fortunately, in many cases, this type of damage can be about magically undone past treating the wood'due south surface with oxalic acid.

Oxalic acid removes the grey colour from oxidized wood, without changing the forest's natural colour. That's why it'due south commonly used as the active ingredient in deck cleaners, and why restorers use it to remove gray or black water stains on furniture (see "Oxalic Acid Undoes Rust," below). Oxalic acid is as well used in some household cleaning products for removing hard water stains, and it has many industrial uses likewise. Although information technology is constitute as a natural ingredient in some vegetables (spinach and rhubarb), oxalic acid is quite toxic if ingested in full-bodied course.

Identify the stains

Every finish repair job is unique, of course, so the commencement step is to thoroughly examine the problem. The breast lid shown hither has both whitish marks (besides called blushing or bloom), and dark grey and black discolorations. White marks are ordinarily in the finish; nighttime discolorations from water indicate more significant damage, because they're down in the wood.

To assist formulate a plan to repair this finish, I dampened the entire hat with mineral spirits [Amazon] (paint thinner). This testing method is useful anytime y'all desire to await closely at either one-time dry finish or bare wood. The await of the paint thinner-dampened surface is similar to how it would look if shellac or a clear oil based finish were practical. In this case, dampening the surface makes the whitish marks temporarily disappear (they reappear when the mineral spirits evaporates). That means a coat or ii of finish is all that'due south needed to have intendance of the white marks. (This is a stroke of luck; if the white marks hadn't disappeared, boosted repair steps would exist necessary to remove them, and that's a topic for some other story.)

Now I can focus on the blackness rings. The mineral spirits examination shows that they get darker, and that makes them good candidates for treatment with oxalic acid. If the oxalic acid works, I won't have to aggressively sand the unabridged lid. Not merely would sanding remove the remaining intact end (80%, in this example), it would also lighten the hat's aged reddish color, and then it would no longer friction match the remainder of the chest that information technology belongs to.

Treat the stains

one. Start by thoroughly cleaning the surface. Kickoff, wipe it down with mineral spirits, to remove polish and other crud that's greasy or waxy. Mineral spirits also shows what the damaged areas volition look like with a articulate cease applied.

Every stride of this treatment should exist washed consistently to the unabridged surface, non but the damaged area. The procedure involves flooding the surface with water. Fortunately, the damage shown here is on solid forest—using this handling on a veneered surface can be risky.

two. When the mineral spirits has evaporated, complete the cleaning process by wiping the surface with lather and h2o, using a soft cloth, to remove water-soluble residuum. Let the surface to dry out completely.

The first pace is a thorough cleaning, using two different cleaners. Mineral spirits removes greasy balance, such as erstwhile wax or polish (Photo 1). Mild dish soap and water removes whatsoever h2o-soluble grime (Photo ii). Neither of these processes volition damage an intact finish.

3. Sand lightly, using fine paper, a soft block and very trivial pressure. Although the goal is to remove the raised grain from the damaged area, it's important to sand the entire surface to maintain consistency.

The grain is raised very slightly in the water-damaged area, then a footling sanding with 400 grit paper is necessary (Photograph 3). This step should take about i minute.

4. Mix a saturated solution of oxalic acrid in a non-metallic container. Add a spoonful at a time to the h2o and stir, until a layer of non-dissolved oxalic acid remains at the bottom.

Mix up a saturated solution of oxalic acid [Amazon] by calculation the crystals to a jar of warm water with a plastic spoon (Photo 4). Do non use any metal containers or utensils—the acid could react with the metallic. Add together crystals a spoonful at a time and stir until no more than will dissolve into the h2o. I always use a saturated solution, so that I have a maximum-strength problem solver.

5. Wipe on the oxalic acid solution. Go out information technology on the surface for well-nigh five minutes to attain the maximum consequence. Then wipe off the backlog and allow the surface dry out thoroughly. The outcome can exist nigh instantaneous.

Wearing gloves and center protection, use a rag or sponge to saturate the entire surface beingness treated, non but the dark spots (Photograph 5). Proceed the surface wet for virtually five minutes to allow for the maximum effect. Then wipe off the excess and let the surface dry out completely. You may see the event immediately as you lot apply the acid, or the spots may disappear gradually, as the acid dries. If a second application of acid is necessary, wait to employ it until the first application has thoroughly stale, or information technology won't work. If two or 3 applications do not remove the stain completely, more acid is not likely to help. You'll have to live with the remaining discoloration or resort to sanding to remove it. All the same, practice non sand until yous have thoroughly rinsed the surface—breathing grit that contains oxalic acid is extremely unpleasant and potentially chancy.

6. Inundation the surface with water repeatedly, to remove any remaining oxalic acid crystals.

When you've completed the oxalic applications, information technology'due south imperative to thoroughly rinse the treated surface with lots of make clean water, to flush away any acid that remains on the wood (Photo half dozen). Flood the surface several times and dry it with a clean cloth or newspaper towel each time. Let the surface dry out between each flooding.

Attempting to "neutralize" the acid that remains on the surface with a mild alkali such as blistering soda, borax or ammonia is a cleansing option that is oftentimes mentioned as an alternative to rinsing. However, I take never seen whatsoever accurate formulas that would make this chemical balancing act a applied possibility. Besides, I know that thorough rinsing works.

Dampen the sur- face with mineral spirits to test the results. Here, the whitish blush areas virtually disappear and the black marks are 99.9% gone. The repair is complete; information technology's time to rebuild the terminate.

Subsequently the lid has thoroughly dried, don a respirator and lightly sand the entire surface with 400 grit paper, to cutting back any grain raised by the oxalic treatments. Test the surface again with mineral spirits, to gauge the results (Photograph vii). The test on this hat indicates that the surface is ready for finishing (Photo viii).

In this example, the finish is blonde shellac, the same finish as the original. Adding a waterproof end over the shellac could help to foreclose hereafter damage. Moving the establish may be a better option.

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