Tried Hypo.. What next?

Even neat hypo didn't do a lot on this sandstone fascia.

Customer asked for jet wash but I put him off. Maybe I should jet wash it after all.

Or maybe Benz would work

Any ideas/

did you pre wet the stone before using hypo?

Yes I wet it.

I could see that it was doing something because the rinse off water was brown. It just didnt really touch the main discolouration.

Pressure washing would damage the stone. Steam would be ok. However, hypo should work but you got to brush it in so that to break down the biofilm.. It’s going to take time & patience.. if it’s black carbon which it looks like then don’t think hypo will shift it.


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Thanks Alec. 

I have walked away from that one now. 

Did you end up getting the benzalkonium from ebay? 

How do you get on with it, I got some on order, Should arrive tomorrow, Im looking forward to trying it.

i was trying to type a reply but the boys came in from work and we all got chatting,bugger me pete you can walk away from the job

and move on?.

i'll leave it as that