Cleaning black limestone - Unsealed and stained!

[RAPressureWashing]

The hypo mix may well balance out the urine staining Laura, as for the sealing you need an impregnating & colour intensifier sealer, this will protect & darken the paving, not necessarily uniform as being a natural stone there can be variations of black, some a bit lighter some a bit darker you won't know until you seal.

[LauraChimes]

Thank you Roger