What's the best way of cleaning sandstone? I've just had large sandstone
terrace laid and the builders have left gobs of cement/paint from the roof/
bits of wood shaving which have ingressed into the sandstone. I live in SE
Asia and getting the builder back to rectify is not an option. They bodgit
and scarper in the finest tradition :-)
The quarry from where we bought the stones say you really shouldn't use acid
but in this case do I have any other option? The material is 600x600x25
slabs. Tx for any help.

Scraping, then muriatic acid wash. Tom