Lichen, what lichen!! - Sandstone Patio cleaning

[Bob_A]

First of all are you sure it's lichen?
Reason I ask is I have sandstone flags and a couple of them have black stuff on them from new, it must of been there when it was quarried.

[Paul Faulkner]

Definitely lichen,these have been down for a few years now and had no evidence of lichen when laid.

[Carberry]

First of all are you sure it's lichen?
Reason I ask is I have sandstone flags and a couple of them have black stuff on them from new, it must of been there when it was quarried.

Good question. I had a customer who wanted me to scrub the slabs with everything, acid, bleach, sandpaper, sandstone, wire brush, pressure washer. Moron wouldn't believe me when I said it's a fossil and if thousands of years of erosion weren't going to shift it I sure as hell couldn't.

[RAPressureWashing]

Paul

Can you put a photo on here so I can see what you have there?

[Paul Faulkner]

This is a worst case flag,most are not as bad as this !!

[RAPressureWashing]

Hi Paul

Have you pressure washed the paving first as it does not look clean from the photo, this will also help remove some of the easier lichen's then you apply the hypo mix while the paving is still damp/wet, for this type of staining I would go in at 1:1 with a 20-30 min dwell time, it might take a couple of applications when they are this covered.

[Paul Faulkner]

The pic was taken before I jet washed.The flag is not much different after washing,treating and washing again.I will try your suggestion and see what happens.I had been applying the mix to dry stone so perhaps wetting will help as you suggest.Thanks for your help and watch this space!

[RAPressureWashing]

Paul,

Yes you have to pre-wet first, that is why if you wash then apply the mix straight away you can have the mix dwelling while you are washing another section.

[hippyjak]

We have an Indian sandstone patio which was laid about 3 years ago. After jet washing it recently we noticed black spots - lichen. We want to get on top of this before it's too late. I read that you suggest sodium hypochlorite whereas on the main page it suggests using calcium hypochlorite?? Which would be the safest on the sandstone. Really don't want to damage our patio, we've waited a long time for it & can't afford to replace it. Any advice would be appreciated

[RAPressureWashing]

We have an Indian sandstone patio which was laid about 3 years ago. After jet washing it recently we noticed black spots - lichen. We want to get on top of this before it's too late. I read that you suggest sodium hypochlorite whereas on the main page it suggests using calcium hypochlorite?? Which would be the safest on the sandstone. Really don't want to damage our patio, we've waited a long time for it & can't afford to replace it. Any advice would be appreciated

sodium hypochlorite, if you make a mix as per my instructions on the stains removal page (main site) and allow a dwell time of 15-20 mins you shouldn't go wrong.

[hippyjak]

Oo ok, haven't found that said yet:p thanks for the quick reply

[hippyjak]

Hi it's me again, could you provide a link to the cleaning page where your instructions are please, soo much information, I'm not sure if I'm looking in the right place

[RAPressureWashing]

This page, the berry & fruit mix.
http://www.pavingexpert.com/stains.htm

[hippyjak]

Thankyou

[dig dug dan]

Would that mix clean a upvc consevatory?