Bluestone hearths are generally cleaned using warm water and dish soap or another pH-neutral cleanser. Bluestone, however, is a vague term that has different meanings in different places. In the United States, the terms bluestone and bluestone slate typically refer to two different types of stone. One, known as Pennsylvania bluestone, is a type of sandstone taken from quarries in New York and Pennsylvania. The other, known as Shenandoah bluestone, is a limestone found in Virginia's Shenandoah Valley. In Australia and other countries, bluestone refers to a type of Basalt or slate. Fortunately, most of the stones called bluestone are classified as siliceous stones, meaning they are made largely of silicates, and are all cleaned using the same methods. It is always wise, however, to test any cleaning method on an inconspicuous area before cleaning your entire hearth.
Sweep up any loose dirt or debris from the hearth using a dustpan and broom. Do not vacuum the stone, as rough vacuum cleaner wheels could scratch the stone.
Take note of and treat any stains on the hearth. To treat a stain, apply the correct solution to the area; dab the stain, and then rinse the area with warm water. Treat stains on bluestone using the following methods:
- Oil-Based Stains: Apply ammonia, mineral spirits or acetone.
- Organic Stains: Spray the area with a 12 percent hydrogen peroxide solution.
- Rust: Purchase and apply a poultice from your local hardware store. The poultice may need to rest on the stain overnight.
- Ink Spots: Use bleach or hydrogen peroxide on light stone. Apply acetone to darker stones.
- Paint: Lacquer thinner will remove small spots. Use commercial paint stripper for large stains.
Wash the stone using a solution of warm water with a few drops of dish soap added to it. Use a damp cloth, but don't saturate the stone. It is best to use a cleaner as close to pH neutral as possible on natural stone. If dish soap isn't doing it and you need something more potent, try an alkaline cleaner like trisodium phosphate (TSP). Always avoid acidic cleaners on bluestone.
Rinse the stone with another clean, damp cloth.
Dry the bluestone with a soft cloth so that it absorbs as little water as possible.