[Smudger]

Did a sandstone job 2 weeks ago very badly covered in black spot, 99% removed everyone happy, until today customer has sent some pictures with black spots all over the stone, apparently it's returning over several areas 

Anyone had or heard of this before ? Suggestions on what I might need to do to remove it on a slightly more permanent basis

Darran

[Matt.]

I dont know so am just guessing, but is this like a living bacteria or mould of some kind and is spreading,  am guessing around the pool in this warm weather, pool getting used and water running across it.

Just a suggestion Darran

Matt

[Smudger]

Thing is the pool will have chorine water so should aid in removal ( a  very light hypo solution really )

It maybe a case that this week was hot and sunny but rainy and dull on the day, perhaps it looks more apparent than before ?

Darran

[Matt.]

You may have to put something along side of pool to prevent run off and do small sections with a chemical that will kill it properly, only trouble is......... What is it called
Am not these best with chemicals but there must be something more specific in killing bacteria/mould lichen, types

By the pic posted it was very bad, ask them if they know what type of bacteria it is and maybe you could then get hold so something to kill it off.

Or maybe hypo 50-50 with water and a deck scrub or scrubbing brush by hand

[Rob@Blast off]

Never known it to return that quick!
My only suggestion to stop it from returning so quick would be to spray it with a fine misting of weak hypo on a dry day and let it dry on.

[wpclean]

Tell them you will give then a 10% discount for re-cleaning, as they are such a good customer 

[Tadgh O Shea]

Hi Darran, just to share most people think that bleach is the best way to tackle mold growth lichen etc, bleach will not kill mold , it merely bleaches it, that's right, not only will mold survive a good bleaching , it'll look as though it's gone, lulling you into a false sense of security, bleach is a disinfectant and not a cleaner  and doesn't really clean dirt and stains from surfaces,  its best to just pressure wash the ingrained soils from the patio slabs, to remove the black lichen spots properly you'd need to scrub them, the most effective tool i have come across for these little buggers are stainless steel scouring pads not the ones you'll find in supermarkets as they are only 15 gram, go to a janitorial supplier and get 40 or 60 gram ones and they will eat through the toughest of lichen doesn't matter how old they are, i know it sounds crazy because you will have to get on your hands and knees to do this with the s/s pads, this leaves you with two choices as all you need to use is water with the stainless steel scouring pads to remove these black lichen spots, you have to educate the customer about the problem, then you can justify the extra cost if you end up scrubbing them, or you ask the customer if they want to carryout the scrubbing themselves if you leave them with some s/s scouring pads, one 40 gram stainless steel scouring pad will cost £1 and will last long enough to remove 100s of these black lichen spots, i know many guys will laugh at this solution but it does work and to spend £1 won't hurt to find out.

[Matt.]

Worth a try, I no u say u only need water with these pads but wouldn't u get even better results with pad and hypo

[chris scott]

Whats the stone being laid on…full mortar bed?

[Kev Martin]

Whether you clean it with hypo, bleach, plain water or coca cola it is quicker with a Mono Rotary Machine fitted with the correct brush usually in this case an SIC brush.  This system will remove it effectively better than anything you can do by hand.

I am currently getting a few people to test an algae and lichen remover we have which is safe,  virtually permanent and works in two hours.  The manufacturers assure me it works, I have seen it working but I just want to complete a few more tests in unprepared venues and then I will report back.

Kevin

[Smudger]

Whats the stone being laid on…full mortar bed?

Yes Chris

[Smudger]

Kev - sounds interesting.

By the way did you get the photos of the marble door step ?

Darran

[chris scott]

Whats the stone being laid on…full mortar bed?

Yes Chris

Is the surrounding ground wet.

[Smudger]

Not particularly the area is slightly raised  ie.. At the far end the garden drops away by about 3 ft over a distance of 20 foot or so, one side boarders next door with fence so no idea what's the other side of that a small grass border strip customers side which was free draining then buildings and drains at the near end

Thinking of trying ammonium  hydroxide

Darran

[chris scott]

Are you sure the stone is not just going "mouldy" from the inside out due to it being continuously damp..no drainage?

[Smudger]

these are defo spots I'll see if I can stick a picture up

Darran

[Smudger]

[Matt.]

Any news on what chemicals to use to clear this or the plan going forward, 

If the flags are wet from underneath and it has come through to the top, is there anything that can be done ?
And maybe if this was cleaned as good as it was possible and sealed would it prevent it from breathing and returning again.

Would it be safe to seal around the pool, I never used sealer so not sure how it drys

[Smudger]

Got some ammonium hydroxide 

Going back next week as stacked out at the mo

Let you know how it goes, that or I'll be on the news 

Darran

[Kev Martin]

Got some ammonium hydroxide 

Going back next week as stacked out at the mo

Let you know how it goes, that or I'll be on the news 

Darran

If you are going down this route make sure you dilute it 5:1 with water