Masonry Magazine March 2003 Page. 27
When done responsibly, post-construction cleandown brings out the true beauty of a masonry building. safety guidelines-written by field service experts - you maximize your chances for a successful, accident-free cleaning job.
5. Thou shalt test before you clean.
Try out your cleaner on a hidden or out-of-the-way part of the surface. Manufacturers usually recommend test-cleaning a four square-foot area. Test each kind of surface and each kind of stain. What dissolves one kind of stain might leave another untouched. What cleans beautifully on one surface might damage another. Not all mistakes in masonry cleaning can be fixed. Test under the same conditions you'll have for cleaning. Test-panels you made in August might not be accurate for cleaning in October when temperatures are lower. Clean with the same dilution and equipment with which you tested.
6. Thou shalt thoroughly prewet the surface with clean water.
This is perhaps the most critical step in giving a building a uniform, clean appearance. Prewetting keeps the cleaner on the surface, where it does its job. The cleaner can't soak into a thoroughly prewetted surface. The water has already done that. As you move down a wall, cleaning as you go, make sure to prewet as you go.
7. Thou shalt apply the cleaner with low-pressure spray or masonry washing brush.
High-pressure spray-above 50 psi-drives the cleaner right into the brick. Once in, it's difficult or impossible to rinse out. Stains result. It's not an issue if you apply with low-pressure spray or a densely packed, soft-fibered masonry washing brush. Stains and residue can also result from letting the cleaner "dry in" to the masonry. Thoroughly prewetting helps prevent drying in. You can also reapply the product for an additional minute or two if the first application is drying out too quickly.
8. Thou shalt rinse thoroughly.
A few passes with a garden hose is not good enough. Weak rinsing leaves stains and residue. On outside surfaces, high-pressure water-rinses of at least 400 psi and four to six gallons per minute are standard. Inside, use lots of clean water and a sponge or soft-fibered brush to rinse the surface. If you don't have lots of clean water, apply a neutralizing solution of two ounces baking soda per gallon of water. Let it dwell for three to five minutes. Then wipe it off with clean water and a sponge or soft-fibered brush.
9. Thou shalt not clean in cold weather without special precautions.
It's best to clean when air and masonry surface temperatures are 40 degrees F or above. It's best not to clean when temperatures are below freezing or will be overnight. Many cleaning compounds depend on chemical reactions to work. Cold slows the reaction. You may try to compensate by over applying, and accidentally damage the masonry.
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