A quick wipe-down usually does the trick when spills occur on wooden floors. However, when they are left unattended for a long period, these spills can instead turn into stains that last. Most stains and dark spots can be removed using sanding and polishing tools.
Shades of the stains vary, ranging from a soft light brown to even as dark as black. If the stain is dark red, it is likely caused by red wine or other food. Black stains are a major problem for owners with wood flooring.
Although wooden flooring generally provides a warm ambiance, some dark spots are too hard to ignore. A dark spot on an otherwise even floor stands out as a sharp contrast against the non-stained parts of the wood.
A distracting sight, indeed. It can also mean that the wooden floor is damaged and needs additional inspection as quality control.
What causes black stains on hardwood floors?
One of the common causes of black stains on wood is iron oxide. It is caused by prolonged exposure to water and, most often, in combination with other metals. The amount of water involved does not affect anything other than the size of the stain.
However, a darker shade means the stain has been left unattended for quite some time. In this case, black stains are caused by the reaction between tannins or tannic acid, a natural acid in wood that dissolves in water, and iron oxide. In other words, these stains are by-products of metal rusting.
Water itself is also another black stain-inducing substance on wooden floors. This is one of the hardest black stains on wood to remove or repair as these stains indicate that water had seeped through the protective outer layer of wood into the deeper layers of the flooring and therefore requires more intensive treatment.
Various ways, including drink spills, urine, and vomit from pets or kids, can cause these stains. Another unassuming way is using a steam mop on hardwood floors, as water can seep through the openings in the wooden floor finish, especially if they are worn and have gaps between the wooden planks.
Repairing water-caused dark stains usually involves a re-coating stage to ensure your wooden floor has adequate protection by applying a new protective outer layer, preventing water from seeping in the future.
Other black stains are easier to remove or are instead surface-level stains. Some examples include surface stains caused by ink spillage. A wipe-down with light household chemicals almost always removes it entirely. Other chemical reagents like bleach can also be used in this situation.
How do we remove black stains from hardwood floors?
The removal of black stains depends on the cause of the black stain on the wooden flooring. If these black stains were caused by iron oxide reactions between metal and wood, another acid is often applied to negate that reaction.
One example is oxalic acid, which is usually found with other removal agents.
Sanding, bleaching, or re-coating of a protective layer are often employed for water stains:
Sanding alone works best for stains that have not penetrated the deeper layers of the wood. Sanding the dark spot can reveal an unstained spot underneath. Don’t sand too much to avoid uneven thickness on the layer.
Bleaching the area before sanding makes stain removal easier as an additional option. White vinegar and hydrogen peroxide are common household bleaches. Overbleaching will cause the area of the wood to be slightly lighter than the rest and lighten the stain on wood floors. When that happens, additional sanding and re-finishing would be required to even out the shade.
Re–coating (or re–finishing) creates a protective outer layer around the wood, preventing water or other substances from seeping through. This is usually the last step of the stain-removal process. Colored coatings would require a shade match with the wooden flooring. Additionally, this protective layer frequently gives a shinier finish, reversing the age of the hardwood floor.
The importance of wooden finish removal before stain-removal
Some wooden floorings would require you to remove their finishing coat before attempting any stain removal method.
For example, if a stain can be seen on a hardwood floor with a polyurethane finish, the surface coating would need to be removed first, and if the flooring is raw or only has an oil finish, removing or prepping before stain removal is not required.
Different methods to remove black stains from hardwood floors
The first step in any method of stain removal is to assess the stain itself. Check the depth of the penetration and how light or dark the stain looks. Next, infer the cause of the stain based on both attributes.
Deep black stains are often caused by water, but sometimes black stains can be only surface level and caused by spillage of other substances such as ink. The method of stain removal can then be decided.
Method I: Using oxalic acid to remove iron oxide stains
(Note: this method is only effective for iron oxide stains. Other types of stains can use method II instead.)
- Determine whether the flooring finish needs to be removed. Yes, if it has a surface coating, no if it is raw wood or oil-based
- Make a paste by mixing oxalic acid with water. Ensure it is consistent without too much water in the paste.
- Wipe the paste onto the stained wood with a dry towel or brush
- After 15-30 minutes, let the paste on the stain dry. The paste can turn slightly yellow.
- Scrape the dried paste off and repeat step 2
- Apply the paste to the whole wooden surface for the last application to even out the wood shade.
- Brush out any excess paste and re-finish adequately
Method II: Sanding, bleaching, and re-coating
- (Optional) Bleach the area of the stained wood before sanding it by
a. using white vinegar combined with an equal ratio of warm water to scrub the stain, b. white vinegar and baking soda paste to spread and scrub all over the stain, then letting it dry, or c. scrubbing hydrogen peroxide directly onto the stain
- Sand the surface of the stained wood adequately.
- Steps 1 and 2 can be repeated before the last stage of this method – re-coating
- Choose coatings of the same color and sheen as the wooden flooring
- Apply the coating to the stain adequately. Additional instructions that may come with different brands of stain should be followed accordingly in this step.
- Wipe off excess stain.
Remove dark urine stains from hardwood floors with home remedies
Black stains are typically caused by reactions with tannic acid in the wood, such as urine, vomit, damp flower pots, and dark circles from water.
Urine stains can be hard to get rid of, especially if they have been there for a long time without being cleaned. Unfortunately, some fabrics and floor types may not be able to remove the stain completely.
In particular, urine can damage hardwood floors by altering the protective coating, so it’s important to prevent pet urine from causing permanent damage.
When removing urine stains, vinegar and hydrogen peroxide can be effective. Mixing white vinegar with warm water can help eliminate dark spots without sanding, but hardwood floors are not recommended as they can break down the finish and cause discoloration.
Hydrogen peroxide can also help remove the pet’s stain and odor from hardwood. However, be careful not to use too much vinegar or water when cleaning floors, as it can lead to excessive moisture and swelling.
To clean black urine stains from greasy hardwood floors, make a dish soap solution and warm water solution and add a pinch of baking soda and hydrogen peroxide (3%) if you like. Take a sponge, soak it in the solution, and dab the stained area. Let the solution sit for a bit, then wipe it away with a soft cotton cloth.
Another option is to use wood bleach. Sand down the stained area first and make sure to follow the safety guidelines on the product. Different stains might require different cleaning solutions; for instance, chlorine is often effective for food, blood, and similar stains. With wood bleach, you might be able to lighten or completely remove the stain.
Lastly, commercial cleaners can also be used to remove black urine stains from hardwood floors. Research the best product, and follow the instructions carefully for the best results. Remember that each stain removal product is different, so choose the right one for your needs.
How to Protect Hardwood Flooring Against Black Stains
It’s important to take some precautions ahead of time to keep your hardwood flooring in top condition and free from unsightly stains.
- Apply wax or finish to protect the floor
- Clean regularly to prevent dirt buildup
- Clean spills immediately
- Use rugs in areas prone to water spills
- Train pets to prevent urine stains
- Use pot saucers under indoor plants to prevent water damage
- Control humidity to prevent staining caused by dampness.