Masonry Magazine June 2007 Page. 28
NEW RULES FOR CLEANING
# 4. Clean Early and Quickly
An Indianapolis mason contractor didn't have enough water on site to clean a new concrete brick car dealership once it was completed. Instead, he waited 60 days until a waterline and hydrant were installed. By then, the smears and films of the high-strength mortar had become too hard for the relatively gentle cleaner to dissolve. Although he had chosen a high-quality cleaner, the clean down was ineffective. The general contractor's idea was to tear it down and start again, at a price tag of $100,000-which he thought the mason contractor should cover.
Don't give mortar smears and films a chance to become as hard as the masonry itself-remove it while it's still relatively soft. It's acceptable to clean most concrete masonry within seven to 21 days of installation. However, high-strength mortars - such as type M or S mortars and grout are another matter, clean those within three to seven days.
Since cleaners for clay brick are more aggressive than those for concrete and simulated stone, the cleaning window is a little different-14 to 28 days is about right.
Whether you're cleaning clay or concrete, the general principal is the same: The earlier you remove the excess mortar within the cleaning time window, the more easily it will come off. With this being said, however, don't clean before the appropriate window of time, as you risk damaging the mortar joints.
# 5. Use the Right Cleaner for the Right Job
How do you know what the right cleaner is for any given masonry? Chances are the masonry manufacturer will be glad to tell you. It's an increasingly common practice for manufacturers to have their products tested by an independent lab to see which cleaners work best, and at what dilution. This crucial information is often supplied automatically in the form of a pallet tag on every cube of masonry. If not, manufacturers will usually be glad to give you their recommendations for cleaning their products. Remember: it's in manufacturers' best interests, as well as your own, to have projects come out looking as beautiful as you can make them.
On a project with multiple masonry types, you may be able to clean the entire building with one cleaner - IF-you clean it early enough in the window of time appropriate and use the mildest cleaner and dilution possible (refer to rules three and four). Otherwise, follow the masonry manufacturer's guidelines for cleaning each type of masonry.
# 6. Never Clean with Raw Acid
Once upon a time, raw acid was all that was available to clean masonry. Since those days, advances in the manufacture of masonry and other construction materials have made use of raw acids, such as muriatic acid, very dangerous. In particular, muriatic acid is impure in content and inconsistent in strength. It can