[gwrightson]

Has any body used hypo on sandstone ?

I have a customer who would like all of the sills cleaning ,a very large house and a number of the sills do have lichen spotting.
Would hypo be detrimental to the sandstone?
Geoff

[Neil Jones]

It's fine

[Neil Jones]

Add a surfactant to help it stick

[Smurf]

Or you could use safer option like algoclear instead of bleach.

Alternatively no chems at all if you happen to own or hire this type system which uses low psi superheated water so not only cleans the soft stone without damaging the substrate but will kill algae, moss and lichen at the same time.
https://www.youtube.com/watch?v=7dJGuRF82-s

[gwrightson]

Interesting video,
looks effective, but painfully slow and I don't have one either.

How ever I do have algoclear I purchased from J Kelly quite a while ago now, not sure if it will still be effective , it must be 4 years ago.  I may well try this option then hypo if not effective.

thanks for reply's.

Geoff

[BDCS]

HS will be fine but watch the lead flashings or they'll be orange