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Posted: Fri Jun 14, 2013 9:52 pm
by 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.
Posted: Fri Jun 14, 2013 10:18 pm
by Paul Faulkner
Definitely lichen,these have been down for a few years now and had no evidence of lichen when laid.
Posted: Mon Jun 17, 2013 12:11 am
by Carberry
Bob_A wrote: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.
Posted: Mon Jun 17, 2013 3:32 pm
by RAPressureWashing
Paul
Can you put a photo on here so I can see what you have there?
Posted: Mon Jun 17, 2013 8:13 pm
by Paul Faulkner
This is a worst case flag,most are not as bad as this !!
Posted: Mon Jun 17, 2013 8:30 pm
by 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.
Posted: Mon Jun 17, 2013 8:45 pm
by 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!
Posted: Mon Jun 17, 2013 8:58 pm
by 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.
Posted: Mon Jun 24, 2013 6:08 pm
by 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 
Posted: Mon Jun 24, 2013 6:29 pm
by RAPressureWashing
hippyjak wrote: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.
Posted: Mon Jun 24, 2013 6:52 pm
by hippyjak
Oo ok, haven't found that said yet:p thanks for the quick reply
Posted: Tue Jun 25, 2013 9:21 am
by 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
Posted: Tue Jun 25, 2013 5:40 pm
by RAPressureWashing
Posted: Tue Jun 25, 2013 11:51 pm
by hippyjak
Thankyou
Posted: Sun Jun 30, 2013 1:14 pm
by dig dug dan
Would that mix clean a upvc consevatory?