How would we clean our brick on the exterior of our home, it has a white powderdy substance on it, but water alone is not removing it. The brick is about 100 years old.
THanks so much

Read Efflorescence: Cause and Control (http://www.masonryinstitute.org/pdf/612.pdf).

Muriatic acid is probably best to use. Power washing can work but can also drive water into the brick and cause more efflorescence or loosen the morter. In extereme case sandblasting is used but I don't recommend it.