How to remove dark water stains from wood?

Wood is a staple material for a lot of things – furniture, flooring, and fences to name a few. While wood can be just as durable as metal and concrete, it’s a known fact that it doesn’t always take on water as well.

Whenever raw untreated wood, or not properly treated wood comes into contact with water, there’s a possibility of water stains.

This guide will provide the different ways on how to remove water stains from wood.

White stains vs black stains

White stains are lightly colored marks that are often formed from the ‘sweating’ of hot or cold glasses resting on a wooden surface. They’re caused by either steam or moisture that pushes into the wood’s finish. Luckily, they’re not permanent and are quite easy to fix.

Dark stains are marks that indicate that water has reached the wood itself, making removal more tedious and difficult. Black stains from iron on wood remove its beauty and cause dark stains.

Why wood develops dark stains and where do they come from?

• Pet urine and poop. Not immediately cleaning up after your pet can cause the excrement to penetrate the finish and stain your wood flooring. The ammonia found in urine is especially reactive with wood.
• Pet vomit. Pet vomit, especially more liquid ones, is one of the reasons for dark water stains on wood. Vomit is also highly acidic, making it even more damaging. 
• Water stains. Spills, leaks, condensation, and steam can all possibly penetrate the wood finish and get directly into the fibers, in which case they’re likely to cause dark staining.
• Bloodstains. Whether it’s from an injury or cleaning up food items, blood can potentially cause dark staining due to its high water content [1] and the presence of iron, which is highly reactive to a lot of things.
• Spilled ink. Ink is like water, only that it results in much darker stains because of the color pigmentation. Ink is also likely to spread and latch onto the wood, making it more of a hassle to remove.

Other ways mold and dark stains develop on a wooden surface

• Poor maintenance. Not regularly cleaning or not cleaning your wooden items at all is a good way to develop both watermarks and damage. Dust and other particles will eventually accumulate on the surface, potentially damaging the finish and allowing moisture to seep through and from within the wood.
• Using steam mops. Steam is basically water in gaseous form. Not properly using a steam mop to clean wooden furniture and flooring can damage the finish and directly expose the wooden surface.
• Wrong cleaning methods. It’s best to use wood-specific and safe cleaning solutions as some commercially available general cleaning agents, such as Ajax and Comet, can potentially end up damaging wooden surfaces.

What happens if you ignore dark stains on the wood?

Besides being unsightly, dark stains indicate that water has reached the wood itself. Unless you’ve re-treated the piece, chances are that there’s a breach somewhere in the finish and it’ll only lead to more eventual stains.

Where a stain is, there is also likely to be swollen fibers which, if left untreated over time, will lead to structural weakness and eventual failure.

How long should hardwood really last?

The longevity of hardwood depends on its tree of origin. In general, hardwood materials average about forever-to-forever if kept indoors given their innate properties. For example, a treated hardwood floor can last up to a decade, but can more than double that amount with the proper care.

Furniture made from Acacia can last well over 40 years and legitimate Burmese Teak usually outlives its buyer, even without a protective finish. To standardize, given hardwood’s higher cost and qualities, with proper maintenance it should last you a good 15 – 20 years.

Best ways to remove dark stains

There’s no denying that watermarks on wood ruin its beauty. Fortunately, there are a bunch of ways on how to get dark water stains out of wood, but one of the most important things to remember is to work on them as soon as you can. Removing a stain while it’s fresh has a higher chance of succeeding and is usually less time-consuming.

Three popular methods on how to remove dark water stains from wood floors and furniture include using hydrogen peroxide; using oxalic acid; and spot sanding and refinement. 

1. Hydrogen peroxide

1. Take a cloth and soak it in 3% hydrogen peroxide. 
2. Press the cloth onto the stain and rub it over to allow the peroxide to seep into the wood.
3. Allow the cloth to soak up the stain by leaving it for about 6 – 8hrs. 
4. Remove and wipe up any excess peroxide.
5. Clean and wipe the area with a wet sponge and redo the peroxide treatment to remove persistent and lingering marks.

2. Oxalic acid

1. Use wood bleach that has oxalic acid. Make sure to dissolve powdered bleach. 
2. Wear eye and hand protection. 
3. Dilute oxalic acid in warm water, following the measures and instructions of a specific brand.
4. Get a clean toothbrush and use it to scrub the bleaching solution into the stain. Work in a circular motion and be careful not to get it on unstained spots.
5. Allow the bleach to sit for a few hours. 
6. Wipe with a wet sponge and soak up any remaining bleach. 
7. Repeat if the stain isn’t fully removed. 

3. Spot sanding and refinement

1. Get 100-grit sandpaper to first remove the wood finish. Take off only a small area just above the stain.
2. Get 150-grit sandpaper and sand along the grain to directly remove black stains from wood. 
3. Clean and wipe the sanded area free of sawdust. 
4. Fill in any holes and refine the sanded area with wood putty. Allow it to dry and clean off any debris.
5. Sand until smooth and reapply the finish. If the wood has become discolored due to repair, stain it with a close-colored shade before reapplying the finish. 

For very light and small stains, you can use a hairdryer to apply heat and simply, buff it away using a dry cloth or buffing pad. Just be sure to use the lowest setting and move it around so you don’t directly heat up the wood. 

Removing old and dark stubborn stains

1. Using a watermark remover

There are commercially available chemical cleaners that are specifically made to remove watermarks without damaging the wood.

Watermark removers are often acid-based solutions that are directly applied to an area with water stains. Nothing fancy, all you’d need is a rag or cloth, or you can even repurpose an old spray bottle to use with these.

2. Using white vinegar

Vinegar is highly acidic, making it an effective stain remover, but can also end up damaging the inner workings of solid wood if used haphazardly.

A lighter concentration of full-strength white vinegar is enough to get rid of most white stains. Use a diluted solution and allow it to slowly seep into the wood to get to the dark stains then fully wipe dry with a cloth or rag.

3. Bleaching

You can use commercial wood bleachers or follow instructions on how to make homemade wood bleach to get rid of watermarks. You can either bleach the spots that have stains or completely strip the entire piece of color so that it appears uniform.

Ideally, you’d want to use a soft sponge and spread the bleach as evenly as possible while keeping the surface you’re working on wet as you progress.

4. Mineral spirits

Mineral spirits are good for getting at persistent stains without having to worry about further damaging the finish. Use mineral spirits to dampen a rag and gently wipe around the areas with watermarks.

These can sometimes darken the areas where they were used, but they will revert to their original look once the spirit evaporates. In case of light discoloration, apply mineral spirit to the entire surface then reapply a fresh coat of wax.

5. If all else fails, sand the wood back

In worst-case scenarios, to get the dark toughest water stains off wood means having to re-sand the entire surface. It may sound tough because it actually is.

If you’re really keen on wanting your wood furniture and floors looking spotless again, then you’ll just have to muddle through.

Use coarse sandpaper (80 – 150-grit) to get rid of most of the finish and higher than 150-grit to strip the wood bare.

For convenience, use at least a palm sander for speed and precision. And a finishing sander to sand with the grain.

What is the best way to remove dark stains from finished wood?

The best, and most convenient, way to remove dark stains from finished wood is to use solutions that don’t damage the finish.

Hydrogen peroxide, commercial watermark removers, and mineral spirits are among the best choices for removing dark water stains from wood without affecting the wood or its finish.

What is the best way to remove dark stains from unfinished wood?

You can simply bleach unfinished wood to get rid of dark stains or use vinegar to buff and polish out watermarks.

The thing is, untreated wood doesn’t have you worrying about the finish, so you can focus on directly working on the wood itself. 

When not to sand wood with dark stains?

 Sanding should be your last resort [2] when trying to remove dark water stains on wood furniture. Unless you’ve tried and crossed out all other options, only then should you go with sanding.

To answer the question, you don’t want to sand water-stained wood at all unless you absolutely have to. 

How to protect wood from staining?

To protect the wood, in general, you’ll want to apply a protective finish, something like a water-based polyurethane coat (Or even a marine-grade polyurethane).

Not only does this shield your precious wood from watermarks, but also from dust and excess moisture build-up. Keeping your furniture and floors in optimum condition is possibly the best way to protect them. 

Do occasional maintenance and periodically clean and polish your wood items to have them retain their luster.

Also, use coasters, pads, and placemats as much as possible to avoid accidentally forming watermarks. 

How to protect unfinished wood from stains?

If it’s a piece you’ll be using regularly, then it’s highly recommended you apply finish to it. Otherwise, you can coat unfinished pieces with 1 or 2 layers of wax and simply store or place them in areas that are least likely to contact water and/or moisture.

Tips for removing dark stains

Dos

• Do always wear gloves when handling chemical and or highly acidic cleaning agents and solutions. 
• Do be aware of visible stains. White means that the stain has only become trapped within the finish, while black means that water has already contacted the wood.
• Do mind the finish. Carelessly cleaning watermarks can potentially damage the finish, ending up with only more work.

Don’ts

• Don’t use unfamiliar or unsafe cleaning agents. There are solutions specifically designed and compatible with wood. 
• Don’t rush. Unless it’s light and surface stains, the removal process takes a couple of hours at best.
• Don’t sand unless absolutely necessary. Sanding should always come in last. 

Conclusion

Let’s face it, stains on clothing are so unsightly and bothersome. If we can’t stand blemishes on our clothes, then what more if we see them on our furniture and floors, right? Although woods are highly durable and aesthetic, it doesn’t really agree with water.

Avoid staining wood by either avoiding accidents or by ensuring that wood is always duly protected. If you do see a spot, don’t panic, it’s probably organic. Just get your vinegar and some rags ready and that spot won’t be there for long.

And if you’re sanding a surface and expect more water splashes you can protect it from watermarks by applying a marine-grade polyurethane.