Hydrochloric acid, also known as muriatic acid, is one of the strongest cleaners available to the average homeowner. As the name suggests, it is actually an acid and can cause damage if used improperly. It can also cause serious injury if it comes in contact with skin or eyes, and the fumes can cause breathing problems, so it should be used with extreme caution. Since it can be hazardous and is a harsh cleaner, masonry experts suggest using hydrochloric acid only as a last resort when other cleaners do not work.
Ventilate the area where you will be working by opening doors and windows and turning on any exhaust fans. If necessary, place fans around the room or area to ensure good ventilation.
Put on gloves, goggles and face mask.
Place an open container of baking soda or gardening lime within easy reach. Baking soda or lime will neutralize the acid in case of a spill.
Mix together one cup ammonia and one gallon of water in a bucket.
Fill another plastic bucket with about one-half gallon of water.
Add the amount of acid to the water as recommended by the manufacturer. In most cases, it will be one part acid for every 16 parts water, which equals 1/2 cup of acid for every 1/2 gallon of water. The exact measurements, however, will depend on the strength of the acid. Most hydrochloric acid is already diluted to about 31 percent. No matter the strength, the acid still must be diluted before use. Be sure to add the acid to the water. Do not add the water to acid, or it could react and splash, causing damage to your skin or the surrounding surface.
Clean a small area with the acid mixture, using a rag and wearing gloves. Be careful not to get the acid mixture on your skin or clothing. Work on a small section at a time so that the acid is not allowed to stay on the tile for more than 10 seconds.
Rinse immediately with water.
Neutralize the tiles you just cleaned by wiping the area with the ammonia mixture.
Rinse the same area thoroughly with water.
Repeat Steps 7-10 on the remaining tiles, working a small section at a time.