[Ryan Tyler]

Afternoon all, 



Quote on a window cleaning job today and the client also has some stone columns & horizontal pillars in the attached photos with some black marks. Didn't have my gear on me so couldn't try to remove them with water and a scrub on the spot, anyone had experience with this sort of thing? I guess it looks a little like lichen but I'm hoping it doesn't need to be pressure washed off — what chemicals would you reccomend? Hypo? Virosol? TFR? Thanks in advance!

[Phil J]

Try a degreaser applied from a backpack via water fed pole, scrub, and rinse that should do the job.

[Smudger]

Soft wash with hypo through a backpack

Not convinced it's algae - looks like somethings been thrown onto the stone - either way that's a good place to start

Darran

[Slacky]

I'd expect to be giving that two applications. I reckon a TFR would get most of it off, lots like something has been thrown at it, so a TFR should resolve that. There also looks like an organic growth on there, which hypo should resolve. Could follow up by trying to flog them a biocide treatment as well.

[Ryan Tyler]

Thanks for the tips guys!

[the king]

Lite pressure wash steam if you have it or tfr may work

[dazmond]

personally id try to clean off a little patch of it with just my hot pure water....this is what i do on plastic cleans all the time to make sure its not anything too stubborn before i put a  price in.....

[JandS]

I'd leave well alone......get somebody that knows what they're dealing with....stain wise and material wise.

[Yada Yada Yada - www.m-clean.uk]

It's pigeon/bird crap