Bleaching wood often becomes a necessary task when you want to repaint a dark piece of furniture and bring it to a lighter shade. It can also be useful before finishing a stained or uneven colored wooden surface. Follow these steps to whiten it with a biphasic solution or with oxalic acid.
Steps
Method 1 of 3: Prepare the Surface
Step 1. Wash it thoroughly
If it's dirty, don't apply bleach right away. Before bleaching the wood, clean it with water using a soft cloth. Carefully remove any buildup or residue of dirt and let it dry. Usually you need to wait a day or two before bleaching can proceed.
Step 2. Put on protective gear
Bleach can be dangerous if it comes in contact with the skin and eyes. Before applying it, put on safety glasses and a pair of sturdy gloves.
As this is a substance that can stain clothing, it is always a good idea to wear old clothing when using it
Step 3. Place the wood in a well-ventilated area
Always choose a ventilated area when handling bleach to avoid lightheadedness and dizziness. An open garage or porch is the perfect place to whiten wood. Since the chemicals contained in bleach are highly corrosive, it is preferable that they do not come into contact with skin, eyes or household items.
Step 4. Apply the paint remover or stain remover with a rag or brush
Get a product formulated for removing paint or wood finishes. It is important to start with a clean surface before bleaching it. The applications depend on the type of solvent you are using, so consult the instructions in the package. Normally it is spread with a soft cloth, left to act for a few minutes and then rinsed.
- Paint strippers can be chemical or citrus-based. The former produce very strong exhalations, but they act within half an hour. Others have a less pungent smell, but work slower and often need to be applied more coats.
- It is usually necessary to let the wood dry for a day or two after using the paint stripper or stain remover.
Method 2 of 3: Proceed to a Biphasic Chemical Bleaching
Step 1. Use biphasic bleach for a lightening effect
If you intend to lighten a wooden surface only slightly, the best method is to use a two-phase chemical solution. It is a non-aggressive approach that will allow you to change the look of the wood without making drastic changes.
Step 2. Mix the two substances that make up the solution
To proceed correctly, read the instructions on the product. Generally you have to mix them in equal parts in a glass or plastic container. Do not use a metal container, otherwise it may be damaged.>
Be sure to read the instructions that come with the package, as some substances need to be applied one at a time rather than mixed together
Step 3. Apply biphasic bleach evenly
Dip a clean sponge into the solution until it is soaked. Pass it along the wooden surface with rectilinear and above all slow and decisive movements. Continue until it is completely covered.
If you need to apply the substances separately, spread them in succession using the same technique. Depending on their composition, you will probably have to wait a few minutes between applications
Step 4. Wash the wood with an equal parts water and white vinegar solution
Do this as soon as you have cleaned the surface with bleach. It is important to neutralize its action and stabilize the pH of the wood between treatments. Then, once used, prepare a mixture of water and 50% white vinegar. With a clean sponge, apply it to the wood the same way you applied the bleach.
Some biphasic bleach kits are sold with a neutralizer. In these cases it is not necessary to prepare the water and vinegar solution
Step 5. Rinse the wood
Take a clean sponge and soak it in water. Pass it over the wood until the water is clear, trying to remove all traces of bleach and vinegar.
Step 6. Let it dry
Times vary based on the type of wood and the combination of substances you used. The instructions in the kit should give you a rough idea of the time you will need. Do not further treat your surface until it is completely dry to the touch.
Step 7. Sand
Use a sheet of sandpaper with a grain size between 320 and 400. Once the wood is dry, sand it gently. This will smooth out any rough areas and eliminate stringy residue.
Step 8. Stabilize the pH again
After sanding, repeat the neutralization process. Make a mixture of water and white vinegar in equal parts, then apply it to the surface. When you're done, clean it with water.
Step 9. Apply the finish
In this way, in addition to obtaining a better result, you can protect the surface. Once it is completely dry, you can proceed to the finishing treatment. Purchase a suitable product from a hardware store and apply it according to the instructions.
Wear safety glasses and a pair of gloves during this step. Chemicals can damage the skin and in some cases produce toxic fumes. If you're working with an oil-based finish, use an activated carbon filter mask to avoid inhaling them
Method 3 of 3: Whiten with Oxalic Acid
Step 1. Use oxalic acid to remove rust stains and weather damage
Oxalic acid not only serves to change the color of the wood, but is also useful in case of wear due to bad weather or rust that requires a lightening treatment.
Step 2. Prepare the oxalic acid
The instructions in the package should give you the directions you need to properly mix the acid. Usually you have to dissolve 350-470 ml in about 4 liters of hot water.
Remember to use a glass or plastic container to hold the lightening substance. Avoid putting it in contact with metal
Step 3. Clean the wood with oxalic acid solution
Use a sponge to apply it. Don't skimp on quantities if you want to lighten it properly. The number of passes depends on how wet the sponge is. Apply enough to cover the surface completely.
Step 4. Let the acid dry on the surface
There are no precise drying times when using oxalic acid. Let it act on the wood, checking it periodically. Once you have reached the desired shade, you can proceed with rinsing.
Step 5. Rinse the surface
Run the water using a sponge or cloth. Continue until it becomes clear and all residues of the whitening solution and acid are completely eliminated.
Step 6. Neutralize oxalic acid with baking soda
Dissolve 2 teaspoons of baking soda in 1 liter of water. Pour the resulting mixture onto the wood to neutralize the acid. Repeat two or three times, then rinse it off with clean water. Leave the wood to dry overnight.
Step 7. Sand the wood
Once the wood is completely dry, sand it down. Get a sheet of 180-220 grit sandpaper and rub it gently until all rough areas are smoothed out and any lint residues are removed.
Step 8. Apply the finish
If it is of good quality, it can improve the appearance of the wood and protect it from future damage. Buy the product in a hardware store and use it following the instructions on the package. Let it dry completely before using the wooden object.
