Old Paint

• 1). Scrape off the majority of the paint with a putty knife.
  
  
• 2). Dip a metal brush into cold water and scrub it against the hardened paint stain.
  
  
• 3). Soak a cloth with paint remover and rub off any paint that was not removed with the metal brush. Test a small amount of the paint remover on an inconspicuous area of the brick to ensure that it does not leave any stains.
  
  

Mortar

• 1). Remove as much mortar as possible with a chisel.
  
  
• 2). Prepare a mixture of 10 parts water and 1 part muriatic acid, which can be purchased at most hardware stores. Put on rubber gloves and rub the mixture on the mortar stains with a hand towel.
  
  
• 3). Allow the muriatic mixture to sit for 15 minutes, then use a garden hose to rinse it off.
  
  

Rust

• 1). Combine 1 gallon of water with 1 pound oxalic acid, which can be purchased at most auto parts stores.
  
  
• 2). Dip a plastic scrub brush into the mixture and rub it against the iron stains. Test a small amount of the solution on an inconspicuous spot to ensure that it does not leave a stain on the brick.
  
  
• 3). Allow the mixture to remain for five minutes, then use a garden hose to rinse it off.
  
  

Efflorescence

• 1). Combine 1/2 cup muriatic acid with 7 1/2 cups of water.
  
  
• 2). Dip a plastic scrub brush into the mixture and work it into the white stains that are caused by salt deposits forming on the brick.
  
  
• 3). Rinse the muriatic acid away using the garden hose.
  
  

Mildew

• 1). Combine 1 cup bleach with 3 cups water. Add a few drops of liquid laundry detergent to the water.
  
  
• 2). Apply the mixture with a scrub brush. Wear rubber gloves to protect your hands.
  
  
• 3). Allow the mixture to sit for 15 minutes, then use a garden hose to rinse it off.