I have been cleaning a patio for a couple who are having a little garden party next Wednesday. After pressure washing there was still a lot of mould and black lichen I couldn't shift with just water so I thought I would do a good job and use some Paveclean from Sealers Direct I had in the van. By the smell of it it is mainly Hypo but at what strength I don't know, on the label it says to apply neat through a sprayer but as I was using a watering can I diluted 50/50 with water. After waiting 10 minutes I swilled down a couple of times with the pressure washer and sprayed the lawn with water. I have emailed the supplier who reckons I will have killed the grass! Sometimes it doesn't pay to try to do too good a job!