- Wear protective gloves, goggles and clothing to prevent burning or irritation from the chemicals you'll be using.
- Mix one part phosphoric acid to six parts water.
- Cover fixtures, painted surfaces and concrete that has been colored with oxides to prevent discoloration from the solution.
- Apply the solution to the stains using a paintbrush or a spray bottle.
- Let the solution sit until the stain fades away. This can take up to 24 hours.
- Repeat application after 24 hours if the stain is not completely gone.
- Mix a solution of 20 to 40 grams oxalic acid to one liter of water for heavy rust stains.
- Apply the solution in the same manner as you would with phosphoric acid but after the stain is removed, neutralize the oxalic acid solution using a mixture of 15 grams sodium bicarbonate to 1 liter of water and do not wash off.
- Brush off efflorescence, which is a powdery deposit that often forms on brick materials, using a dry stiff-bristled brush.
- Hold a dust pan beneath the brush as you work, or vacuum dislodged bits when you are finished. The salts from the efflorescence must be removed to prevent them from re-entering the brick or other porous material nearby.
- Pick up remaining residue using a damp cloth. Do not use a hose to rinse, this will cause the salt to absorb into the material and reappear again after drying.
- Mix one part muriatic acid to 15 parts water to clean stubborn efflorescence stains.
- Brush on with a stiff bristled brush and rinse with water when the stain is gone.
- Saturate the stains with paint remover containing methylene dichloride.
- Scrub the area with a stiff brush to loosen the paint and rinse with water.
- Scrub remaining paint with a scouring powder until all paint is removed and rinse once more with clean water.
- Mix sodium hydroxide and diatomaceous earth into a thick paste to remove stubborn paint stains.
- Apply a thick layer and let sit on the stain for at least 24 hours before spraying the area with a hose to rinse the paste off the wall.
- Mix 500 grams of sugar soap into 2 liters of hot water.
- Apply the solution to the stained surface using a brush until the stain is removed
- Scrub the area with detergent and a scouring powder containing sodium hypochlorite.
- Mix a solution of one part household bleach to three parts water and a bit of laundry detergent.
- Scrub the solution onto the stain using a brush.
- Let the mixture set for about 15 minutes and then rinse with clean water.