VIDEO TUTORIAL Black slate is subject to staining and whitening easily. Here's how to restore it with BRIGHTSTONE NERO (Marbec) BRIGHTSTONE product sheet: https://www.marbec.it/en/product-catalog/Correttore-Impregnante-Marmo-ArdesiaNera-BrightstoneNero.html For information and assistance: website: www.marbec.it tel: +39 0573959848 Whatsapp: +39 334 857 8502 email: contatti@marbec.it