Examine the labels of any cleaning products you have for cleaning your white limestone fireplace and hearth to verify they are safe to use. Using an acid-based cleaner can eat away at the limestone -- a porous, sedimentary rock that consists of calcite or dolomite -- and damage it.
During the months you use the fireplace, vacuum up soot, dirt and debris frequently to keep these materials from impregnating the limestone. Before you clean it with a mild alkaline or pH-neutral cleaner, vacuum to remove gritty dirt that can damage your fireplace and surround.
Cleaning Agents to Avoid
Do not use any of the following chemicals or cleaning agents on limestone:
- Lemon juice.
- Commercial products that remove lime.
- Acid-based cleaning agents.
- Tub, tile, grout and bathroom cleaning agents.
- Soft-scrub or powdered cleansers.
- Ammonia-based sprays or cleaners.
- Household bleach.
- Metal scrubbers or scrub pads.
Cleaning White Limestone
Vacuum thoroughly before applying a mild alkaline cleaning agent or pH neutral commercial stone-cleaning product.
Add a few squirts of an alkaline-based detergent to a deep bowl of distilled water after vacuuming the fireplace surround and hearth with the soft brush and wand attachment; swish to make light suds. If using a commercial stone-cleaning product, spray it directly on the area that requires cleaning.
Soak a soft, lint-free cloth in the alkaline detergent or distilled water if using a stone cleaner. Wring the cloth out and wipe down the limestone. Continue cleaning the entire hearth with the alkaline-based cleaning agent or the commercial stone-cleaning product.
Rinse out the cloth until no soap residue remains. Wring it out in a bowl or bucket of clean distilled water and wipe down the white limestone to remove any remaining soap residue.
Dry the limestone fireplace and surround with the second lint-free cloth.
Specialized Stain Removal
Before you can remove stains from limestone, you must identify them first to ensure you use a commercial product designed for limestone. Some of the specialty stain removers for limestone include smoke removers, alkaline-based degreasers, oil-based removers -- applied as a poultice to draw out the oils -- cleaning and protection products and more.
Once you have thoroughly cleaned the limestone fireplace, hearth or surround and is once again white, seal the limestone with an impregnating sealer to protect it from future staining. Apply an impregnating sealer only after the limestone is clean and free of any other coatings.
Protect surrounding areas with plastic sheeting and masking tape to guard walls and flooring from the sealer spills or drips. Apply the sealer with a paintbrush, a roller or paint sprayer, allowing it to sit -- based on the product's instructions -- on the limestone for up to 30 minutes. Wipe off excess sealer before it dries. Apply a second coat about an hour after removing the excess of the first coat. It takes up to 48 hours for most sealers to fully cure.