Muriatic Acid

• The most commonly used to clean tile is muriatic acid. Muriatic acid is highly effective in removing efflorescence and cementitious products from the surface of tile, but it is highly ineffective at removing organic material. Muriatic acid is highly toxic, burning the skin with contact. Additionally, it is dangerous to breathe muriatic-acid fumes.
  
  

Sulfamic and Phosphoric Acid

• Sulfamic and phosphoric acid are crystals added to water in a one-to-five (crystal to water) mixture. They are primarily effective in removing efflorescence and lime deposits from tile and grout. Unlike muriatic acid, sulfamic and phosphoric acids do not emit dangerous, burning vapors. Mixing either of these acids with hot water increases acidity but is dangerous.
  
  

Acetic Acid

• Vinegar is an acetic acid used to clean tile. The Ceramic Tile Institute of America (CTI) notes that people use acetic acids such as vinegar without understanding that the seemingly benign acid can damage tile.
  
  

Suited Purpose

• The CTI also notes that acids are not to be used to remove a "heavy film of grout or Portland cement," and that acids will not remove thick coatings of grout or cementitious materials. Additionally, it is improper to use acid to remove oil, grease and paint. Further, CTI states that many stains will actually become more stubborn after being "subjected to an acid bath."
  
  

Requirements and Technique

• CTI notes that only tile-industry experts should use acid to clean tile and that 14 days must pass before using an acid cleaner on fresh tile. CTI also notes that acids will permanently damage flooring grout that has not had time to cure, and that newly installed floors should never acid-cleaned. A clean tile surface is necessary as are the proper tools to perform an acid-cleaning job.
  
  

Performing an Pre-Acid Test

• The CTI recommends performing an acid test on ceramic tile. To perform an acid test, simply drip a silver dollar-size amount of pure lemon juice on a piece of tile (preferably an extra piece or an inconspicuous area). Allow 24 hours for the lemon juice to stand on the tile. If discoloration takes place after 24 hours, chance are you should not clean the remaining tile with acid. CTI notes that this test is particularly important regarding glazed ceramic tile.