It is advisable to maintain careful records about the
type of stone, name, and origin of the stone existing in your
building. If such records do not exist, you should
explore the following options before determining a
cleaning and maintenance program:
1. Consult with a professional stone supplier,
installer, or a restoration specialist to help identify
ther your stone is siliceous or calcareous.
3. Conduct a simple acid sensitivity test to
determine if your stone is siliceous or calcareous.
You will need:
• 4 ounces of a 10% solution of muriatic acid
or household vinegar
Because the test may permanently etch the stone,
select an out-of-the-way area (a corner or closet)
several inches away from any mortar joint. Apply a few
drops of the acid solution to the stone surface on an
area about the size of a quarter. Two possible reactions will occur:
1) Acid drops will bubble or fizz vigorously – a sign that
the stone is calcareous.
2) Little or no reaction occurs – stone can be
considered silicous. See note below.
Rinse the area thoroughly with clean water and wipe dry.
NOTE: This test may not be effective if surface sealers or
liquid polishes have been applied. If an old sealer is
present, chip a small piece of the stone away and
apply the acid solution to the fractured surface.
CAUTION: Muriatic acid is corrosive and is considered
to be a hazardous substance. Proper head and body
protection is necessary when acid is used. Again, it is
always wise to consult with a stone professional if you
are unable to visually identify the stone and/or are
uncomfortable using the acid test.