A common name for a stone used in patios and outdoor walkways, bluestone comes in multiple colors including tan, purple, rose, green and gray. A siliceous stone composed of quartz or silica; it develops white, crystal-like mineral salt deposits on its surface when exposed to dry air. Known as efflorescence, the dry air evaporates water in the stone leaving mineral salts on its surface. Numerous products are available to get rid of persistent efflorescence, but inexpensive and immediate removal is done with tools found around the home.
Things You'll Need
Vacuum with wand
Dry Clean the Stone
Briskly wipe the affected bluestone using a dry or electrostatic mop.
Place a mat on top of the bluestone and place the vacuum on the throw rug to protect the bluestone surface from any worn parts underneath the vacuum.
Vacuum the affected bluestone using the brush attachment and the wand. Ensure there are no objects on the attachment that could scratch the stone.
Repeat steps as necessary to get rid of the crystals.
Using A Cleaner
Put on rubber gloves to protect your hands from the acid cleaner.
Spray or wipe the affected area with a slightly acidic cleaner such as phosphoric acid and let the cleaner sit for a minute or two.
Wipe up the cleaner using a slightly damp sponge. Do not soak the stone when wiping up the cleaner. Repeat until crystals are gone.
The Marble Institute of America advises against hosing off stones affected by efflorescence as this will increase the problem. The best way to reduce problems with efflorescence is to reduce the stone's exposure to water or to coat it with a sealant to prevent water from soaking it. Most problems with efflorescence disappear as the stones dry. If the problem persists, find the source of the excess moisture and eliminate it.
If you don't have experience dealing with acid or acidic cleaners, it is best to hire a professional to remove stubborn efflorescence. Do not use muriatic acid. It is very strong and dangerous and should only be used by a professional.