Hi from Canada,

My mother has had a Japanese Stone Lantern in her backyard for years. Only the two top pieces, exposed the most to the elements, have discolored to an ugly dark grey. The base pieces are still their original light grey. Does anyone know how I can clean the stone myself? She's moving to a condo and is planning to leave it behind but I'd like to try to sell it for her as she's a senior on a fixed income.

Thanks so much.