Author/Submitted by: Polly's Pointers,
Shared by Sherilyn Schamber
Scrub with a strong solution of washing soda and water with a stiff brush. Steel wool and scouring powder also work well.
Apply a paste of concentrated ammonia and powdered pumice. Leave this mixture on for a couple of hours then scrub with a stiff brush and hot water.
Scrub with cider vinegar and a stiff brush. Blot with a sponge or paper towel, then rub with a towel that has been dipped in clear water.
Add 4 oz yellow laundry soap to enough hot water to make a qt of soft soap. Heat until soap dissolves, cool, and then stir in 1/2 lb powdered pumice stone and 1/2c household ammonia. After mixing well, scrub stones with a stiff brush. Use a clean brush to apply another coat of the cleaning mixture and leave it on about 15 minutes. Scrub off with the brush and clean warm water. Rinse with more clear water.
Scrub with equal parts liquid bleach and water.
Spray a heavy coat of oven cleaner on the bricks. Let it stand a while, then rinse off with water and a sponge. Be sure to protect the surrounding area, including floor, carpet, and adjoining wall from the cleaner by covering with newspaper or plastic.
Once you've got those bricks or stones clean, apply a coat of linseed oil. It helps maintain the beauty of unpainted brick, stone, and slate, and makes them easier to clean.
Always rinse thoroughly after cleaning.