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Black and white spots on patio pavings

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Bouleversee
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Black and white spots on patio pavings

#430107

Postby Bouleversee » July 24th, 2021, 12:34 pm

Has anyone found a way of removing these and stopping them returning without spending a fortune? Mine is York stone and 2 products I have tried have had no perceptible effect. I don't want to have to pressure wash as it destroys the grouting between the crazy paving. My patio is quite large and I have paths and steps as well.

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Re: Black and white spots on patio pavings

#430119

Postby stewamax » July 24th, 2021, 2:32 pm

It's just benzalkonium chloride. And BAC50 (concentrated) benzalkonium chloride is best bought in quantity from chemical firms such as Bonneymans.
The stuff is not really a patio cleaner per se but a lichen and algae killer, and for this is it very good. I use it on close-board and palisade fencing to prevent lichen build-up. So whether or not is it useful for your patio depends on what staining it has.

Two caveats:
- don't use anywhere where a cat may lie: they lick it and get sick (mouth ulcers, temperature...)
- use goggle-type eye protection and wash your hands afterwards: concentrated BAC can cause serious eye injury although in extremely dilute form is actually used as a preservative in eye drops!

Bouleversee
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Re: Black and white spots on patio pavings

#430122

Postby Bouleversee » July 24th, 2021, 2:42 pm

Many thanks, RVF. I was aware of Patio Magic and its price is certainly very cheap compared with others. However, I note that lichen (which is the cause of the black and white stains) is only mentioned on the 5l bottle with pressure spray on their website, though I thought I had seen it mentioned elsewhere without a spray, which I don't need. Which type did you use and did you have black/white areas or just green which is easy to deal with with bleach solution, which unfortunately doesn't seem to work on the lichen damage?

Bouleversee
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Re: Black and white spots on patio pavings

#430123

Postby Bouleversee » July 24th, 2021, 2:49 pm

Stewamax -

I was told that the black and white stains are caused by lichen but you may know different. Does it get rid of those stains or not? Some (very expensive) products claim they work on those stains immediately (sometimes after pressure washing as well) and others say it takes some time to see a difference. All very confusing.

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Re: Black and white spots on patio pavings

#430132

Postby bungeejumper » July 24th, 2021, 3:58 pm

stewamax wrote:It's just benzalkonium chloride. And BAC50 (concentrated) benzalkonium chloride is best bought in quantity from chemical firms such as Bonneymans. The stuff is not really a patio cleaner per se but a lichen and algae killer, and for this is it very good.

BAC (as in Patio Magic), or its near-relative DDAC, are both extraordinarily good on flat stone-type surfaces. Their main function is as a bactericide - they are used in tiny (1% to 2%) dilutions in hospitals. I use DDAC in a 2% dilution on a limestone gravel drive, about the size of a tennis court, to keep moss and lichen down.

Which will give you an idea of how scarily powerful these chemicals are at a 50% dilution. :shock: Do take Stewamax's warnings about handling BAC50 or DDAC50 seriously - it can irreparably damage your eyes, so be careful if you agitate it with a toothbrush, etc. Even at 2%, it's instant death to a fishpond (and not good for pets until it's absolutely dry). I have a 5 litre can, which will last me the rest of my life. A litre would have been more than sufficient for eight or ten years. :?

Manufacturers are no longer allowed to advertise these chemicals as a remedy for moss. (Not sure about lichen?) Moss was technically reclassified as a plant some years ago, and these chemicals aren't on the approved list. They still work, though.

TBH, I'd be tempted to just scrape the black spots off those paving stones and then let them colour down naturally. It won't take long.

BJ

88V8
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Re: Black and white spots on patio pavings

#430134

Postby 88V8 » July 24th, 2021, 4:09 pm

Bouleversee wrote:... lichen ...which is the cause of the black and white stains... lichen damage?

Lichen is an indicator of clean air.
You should be very pleased to welcome it into your garden.

We have a great deal of lichen in our garden, on tress and shrubs and on paving. I would not dream of killing it. No wonder the planet is in such a mess when we casually reach for chemicals to obliterate nature. Although I do make an exception for moss on steps, where I use Jeyes Fluid.

More about lichen here https://www.nhm.ac.uk/discover/nature-a ... c-air.html

And we have at least two varieties of lichen on the never-washed roof and bonnet of my Land Rover, which I refer to as 'patina'.

V8

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Re: Black and white spots on patio pavings

#430135

Postby Dod101 » July 24th, 2021, 4:11 pm

I power wash but Bouleversee is correct, it does tend to loosen the grouting but frost does that as well so I am resigned to having to repair it anyway. My paving slabs get surprisingly dirty and a power wash cleans them. It does not though remove very small black spots but I am not sure that I am fussed enough to worry about them.

I have plenty of lichen and fresh clean air. I do not like moss on my house roof though because it by its nature attracts dampness

Dod

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Re: Black and white spots on patio pavings

#430137

Postby Bouleversee » July 24th, 2021, 4:20 pm

bungeejumper wrote:
stewamax wrote:It's just benzalkonium chloride. And BAC50 (concentrated) benzalkonium chloride is best bought in quantity from chemical firms such as Bonneymans. The stuff is not really a patio cleaner per se but a lichen and algae killer, and for this is it very good.

BAC (as in Patio Magic), or its near-relative DDAC, are both extraordinarily good on flat stone-type surfaces. Their main function is as a bactericide - they are used in tiny (1% to 2%) dilutions in hospitals. I use DDAC in a 2% dilution on a limestone gravel drive, about the size of a tennis court, to keep moss and lichen down.

Which will give you an idea of how scarily powerful these chemicals are at a 50% dilution. :shock: Do take Stewamax's warnings about handling BAC50 or DDAC50 seriously - it can irreparably damage your eyes, so be careful if you agitate it with a toothbrush, etc. Even at 2%, it's instant death to a fishpond (and not good for pets until it's absolutely dry). I have a 5 litre can, which will last me the rest of my life. A litre would have been more than sufficient for eight or ten years. :?

Manufacturers are no longer allowed to advertise these chemicals as a remedy for moss. (Not sure about lichen?) Moss was technically reclassified as a plant some years ago, and these chemicals aren't on the approved list. They still work, though.

TBH, I'd be tempted to just scrape the black spots off those paving stones and then let them colour down naturally. It won't take long.

BJ

It doesn't scrape off and even if it did, life is too short.

Bouleversee
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Re: Black and white spots on patio pavings

#430140

Postby Bouleversee » July 24th, 2021, 4:40 pm

Thanks but you haven't answered my question. All these products work on green algae and moss but did you have black and white areas which are such a problem to get rid of?

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Re: Black and white spots on patio pavings

#430141

Postby kiloran » July 24th, 2021, 4:44 pm

Bouleversee wrote:Thanks but you haven't answered my question. All these products work on green algae and moss but did you have black and white areas which are such a problem to get rid of?

Here's a fairly comprehensive article on lichen problems
https://www.pavingexpert.com/maintain_03

--kiloran

AsleepInYorkshire
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Re: Black and white spots on patio pavings

#430142

Postby AsleepInYorkshire » July 24th, 2021, 4:47 pm

Bouleversee wrote:Has anyone found a way of removing these and stopping them returning without spending a fortune? Mine is York stone and 2 products I have tried have had no perceptible effect. I don't want to have to pressure wash as it destroys the grouting between the crazy paving. My patio is quite large and I have paths and steps as well.

Jeyes Fluid

Be patient with it - I've used it on my block paved drive for over 20 years. Buy the concentrated stuff and dilute it. I never bother with brushing or anything else. I tip it on early spring and end of summer.

AiY

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Re: Black and white spots on patio pavings

#430143

Postby bungeejumper » July 24th, 2021, 4:50 pm

88V8 wrote:Lichen is an indicator of clean air.
You should be very pleased to welcome it into your garden.

We have a great deal of lichen in our garden, on tress and shrubs and on paving. I would not dream of killing it. No wonder the planet is in such a mess when we casually reach for chemicals to obliterate nature.

Yes, I'm in qualified agreement with you. Our stone-built Victorian house looks great with a spattering of lichen, and we've even resorted to painting some stone surfaces with cow dung to encourage it. (Live yoghurt is nearly as good, but with our luck, animals would probably come along and lick it off. :lol: ) But it can look pretty messy on modern buildings where the architects wanted the surfaces to be crisp and clear.

Unfortunately we "casually reach for chemicals to obliterate nature" every time we fill up the car or put disinfectant down the drains. And Jeyes fluid is just as nasty to life forms (including cats, worms and pond life) as BAC or DDAC. And its carcinogenic as well. Everything in moderation. :|

BJ

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Re: Black and white spots on patio pavings

#430145

Postby Bouleversee » July 24th, 2021, 5:09 pm

kiloran wrote:
Bouleversee wrote:Thanks but you haven't answered my question. All these products work on green algae and moss but did you have black and white areas which are such a problem to get rid of?

Here's a fairly comprehensive article on lichen problems
https://www.pavingexpert.com/maintain_03

--kiloran

Yes, I read that earlier today and wanted to ask a question so have registered but have to await a further email of them before I can ask my question.
I use diluted bleach on my front steps and path and they don't have the stains but it doesn't seem to work on the patio which someone talked me into letting them use a pressure washer some years which has wrecked much of the grouting and the stains are back with a vengeance despite using patio cleaners in subsequent years. I applied one earlier in the week which doesn't seem to have had any effect. I have read elsewhere that bleach etches natural stone and the patio cleaners emphasise that they don't include it. Having read on the linked website that bleach solution is often used, I shall try it on the patio of there is no improvement but I have a feeling it may have gone too far for that.

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Re: Black and white spots on patio pavings

#430148

Postby Bouleversee » July 24th, 2021, 5:22 pm

88V8 wrote:
Bouleversee wrote:... lichen ...which is the cause of the black and white stains... lichen damage?

Lichen is an indicator of clean air.
You should be very pleased to welcome it into your garden.

We have a great deal of lichen in our garden, on tress and shrubs and on paving. I would not dream of killing it. No wonder the planet is in such a mess when we casually reach for chemicals to obliterate nature. Although I do make an exception for moss on steps, where I use Jeyes Fluid.

More about lichen here https://www.nhm.ac.uk/discover/nature-a ... c-air.html

And we have at least two varieties of lichen on the never-washed roof and bonnet of my Land Rover, which I refer to as 'patina'.

V8


I have grey, frilly lichen on dead branches of trees and on one of my azaleas which is clearly dying whereas the others are fine and don't have any lichen. I didn't notice any when I moved here in 2008 when the air was much less polluted than it is now as a result of greatly increased traffic since then. I now sometimes smell fumes coming from the road at the end of my garden. I note that the paving under the roof of the overhang where my house is single storey is not stained so I had assumed that it must be something in the rainwater which is causing the black staining and spotting. It really looks a mess.

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Re: Black and white spots on patio pavings

#430151

Postby Bouleversee » July 24th, 2021, 5:31 pm

Dod101 wrote:I power wash but Bouleversee is correct, it does tend to loosen the grouting but frost does that as well so I am resigned to having to repair it anyway. My paving slabs get surprisingly dirty and a power wash cleans them. It does not though remove very small black spots but I am not sure that I am fussed enough to worry about them.

I have plenty of lichen and fresh clean air. I do not like moss on my house roof though because it by its nature attracts dampness

Dod


I take it you don't have crazy paving (not installed by me, I hasten to add) which has been grouted with Italian pointing i.e. going to a point in the middle. Nightmare!

Do you treat the moss on your roof? My son was planning to spray my roof (single storey) as some of it is under trees and gets very mossy. Appropriate weather conditions and his availability never seem to coincide, however.


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