How to clean a headstone?

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Light soil can be cleaned off with just a light washing and water. More stubborn grime can often be cleaned off with a soft-bristled brush and a mild cleaner. Avoid using household cleaners that contain sodium carbonate, sodium bicarbonate, sodium chloride, sodium sulfate or ammonium carbonate. These chemicals can create salt deposits on the monument. Choose a product that's biodegradable, non-corrosive and not abrasive.