The marble under the carpet in my customer’s front foyer has yellowed. What can I use to remove the yellowing?

The yellowing is the result of moisture becoming trapped under the carpet. The carpet’s jute backing or dyes from its rubber backing have bled into the stone. To remove this yellowing, try the following steps:

Clean the area with a solution of an alkaline stone cleaner. Be sure to rinse thoroughly. If this fails, a poultice may have to be applied.

Apply a poultice of diatomaceous earth and a solvent such as mineral spirits. For detailed instructions, refer to my book “Stain Removal Guide for Stone”.