Hi, I use a product called Marblack its very good and very easy to use, just clean the slate with warm soapy water, dry it off and leave it overnight then with a soft cloth rub the Marblack on leave it 24hrs (Then if needed give it a second coat wait 24 hrs)then polish with beeswax and it will shine like a new penny....I get it from a company call Meadows & Passmore in Brighton Sussex U.K. maybe you can get it locally any more help i can give email me at delboy4410@yahoo.co.uk regards...
MARBLE CLEANING/VALUE by: Anonymous
BLACK BOOT POLISH WORKS VERY WELL FOR ME,YOU NEED TO BULL LIKE YOU WOULD DO YOUR ARMY BOOTS,YOU NEED TO BUILD UP THE LAYERS,IT TAKES TIME AND PATIENTS,THE ONLY WAY TO FIND THE PRICE DEPENDS ON CONDITION OF THE MOVEMENT AND THE CASE,CONDITION IS EVERYTHING.ONCE CLEANED AND SERVICED IT WILL ATTRACT BUYERS THE ONLY WAY TO FIND OUT IS BUT IT IN AUCTION WITH A RESERVE,BE WARNED YOU MAY THINK YOU HAVE THE CROWN JEWELS BUT THE MARKET WILL TELL YOU THE TRUTH.