From My wiki
Cleaning marble can seem challenging at first, however, a simple solution of caustic soda will do most of the work for you.
- Prepare a strong caustic soda solution.
- Soak your stained marble for a period of 5 days to two weeks. The strength of the solution directly affects the speed with which the grime is removed. Experimentation is key here, but 100 grams of caustic soda to 10 litres of water will generally tackle any staining you have.
- Use the pressure sprayer to hose your marble down. This should remove all of the dirt.Make sure to wear gloves. Caustic soda can irritate the skin and may even cause chemical burns after prolonged exposure.
- Use a fine emery paper to touch it up if there's any staining left, but be careful.
- A strong solution will strip away paint.
- Caustic soda can cause chemical burns.
Things You'll Need
- a container large enough to contain your marble piece
- a high pressure sprayer
- caustic soda
- rubber gloves and protective eyewear