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Indian Sandstone Patio - Restore colour with Karcher?

  • 13-04-2020 03:11PM
    #1
    Registered Users, Registered Users 2 Posts: 639 ✭✭✭


    Patio is in place approx 12 years and is looking very tired, most of the original colour is now faded to a dull grey with a lot of black algae spots.
    Any previous attempts to clean it have only resulted in removing the grime and brightening the stones but not shifting the algae and certainly not restoring the colour.

    From a small bit of research, it looks like I need a very powerful washer?
    I was looking at this Karcher K7

    https://www.kaercher.c...s-home-13171360.html

    It's quite expensive so was wondering what people's thoughts are?


Comments

  • Registered Users, Registered Users 2 Posts: 2,115 ✭✭✭monkeynuz


    JMR wrote: »
    Patio is in place approx 12 years and is looking very tired, most of the original colour is now faded to a dull grey with a lot of black algae spots.
    Any previous attempts to clean it have only resulted in removing the grime and brightening the stones but not shifting the algae and certainly not restoring the colour.

    From a small bit of research, it looks like I need a very powerful washer?
    I was looking at this Karcher K7

    https://www.kaercher.c...s-home-13171360.html

    It's quite expensive so was wondering what people's thoughts are?

    No, you dont need a really powerful one.

    Get some sodium hyperchlorite and apply to pre wet paving at 5:1 initially, brush in then leave for 30 minutes then pressure wash with average power machine, spend a few seconds dwelling on the algae spots. If it doesnt shift it all at once then repeat with stronger solution down to neat.

    Btw dont let it dry on the stones.


  • Registered Users, Registered Users 2 Posts: 639 ✭✭✭JMR


    monkeynuz wrote: »
    No, you dont need a really powerful one.

    Get some sodium hyperchlorite and apply to pre wet paving at 5:1 initially, brush in then leave for 30 minutes then pressure wash with average power machine, spend a few seconds dwelling on the algae spots. If it doesnt shift it all at once then repeat with stronger solution down to neat.

    Btw dont let it dry on the stones.

    Thanks for the reply.
    Presuming that the sodium hypochlorite is for removing the algae spots, will it do anything to restore the colour of the stone?


  • Registered Users, Registered Users 2 Posts: 2,115 ✭✭✭monkeynuz


    JMR wrote: »
    Thanks for the reply.
    Presuming that the sodium hypochlorite is for removing the algae spots, will it do anything to restore the colour of the stone?

    It will do the lot....you will be dazzled by the results, it's quite a shock when you first do it!


  • Registered Users, Registered Users 2 Posts: 2,115 ✭✭✭monkeynuz


    Whereabouts are you? Do you have a farm supply place nearby?


  • Registered Users, Registered Users 2 Posts: 13,179 ✭✭✭✭Calahonda52


    Sodium hypochlorite is alkaline, and household bleach also contains NaOH to make the solution even more alkaline. Two substances are formed when sodium hypochlorite dissolves in water. These are hypochlorous acid (HOCl) and the hypochlorite ion (OCl-), with the ratio of the two being determined by the pH of the water.
    Limestone is soft so the HOCI will dissolve the stone if left too long/too strong

    “I can’t pay my staff or mortgage with instagram likes”.



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  • Registered Users, Registered Users 2 Posts: 2,115 ✭✭✭monkeynuz


    monkeynuz wrote: »
    No, you dont need a really powerful one.

    Get some sodium hyperchlorite and apply to pre wet paving at 5:1 initially, brush in then leave for 30 minutes then pressure wash with average power machine, spend a few seconds dwelling on the algae spots. If it doesnt shift it all at once then repeat with stronger solution down to neat.

    Btw dont let it dry on the stones.

    When I said neat I meant 1:1


  • Registered Users, Registered Users 2 Posts: 2,115 ✭✭✭monkeynuz


    Sodium hypochlorite is alkaline, and household bleach also contains NaOH to make the solution even more alkaline. Two substances are formed when sodium hypochlorite dissolves in water. These are hypochlorous acid (HOCl) and the hypochlorite ion (OCl-), with the ratio of the two being determined by the pH of the water.
    Limestone is soft so the HOCI will dissolve the stone if left too long/too strong

    Up to half an hour or so works fine.


  • Registered Users, Registered Users 2 Posts: 639 ✭✭✭JMR


    monkeynuz wrote: »
    Whereabouts are you? Do you have a farm supply place nearby?

    I am in Dublin and not surprisingly, I don't even know what a farm supply place is, never mind whether there's one nearby :o

    Household bleach will not do the job, will it?


  • Registered Users, Registered Users 2 Posts: 31,006 ✭✭✭✭HeidiHeidi


    Hi, I replied on your other thread, but this one seems to be getting more traction, so.....


    If you want to get rid of the algae spots/staining, I can recommend Algon - I got it in my garden centre, spray it on and leave it to dry in (perfect weather at the moment) and it works over a few days. If the problem is bad, I would guess that a few repeated applications might be needed.


    As regards restoring the colour - I really don't see how bleach or chemicals or power washing would do that? I would really love to get the colour back into mine as well, so hoping that someone comes along with a suggestion!


    But I think there's two separate problems here......


  • Moderators, Regional Midwest Moderators Posts: 11,251 Mod ✭✭✭✭MarkR


    I have the same problem, following this with interest. :-)


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  • Registered Users, Registered Users 2 Posts: 2,115 ✭✭✭monkeynuz


    JMR wrote: »
    I am in Dublin and not surprisingly, I don't even know what a farm supply place is, never mind whether there's one nearby :o

    Household bleach will not do the job, will it?

    Household bleach will to s point but you'll need much more and it isn't as effective.

    Try any hardware stores near you.


  • Registered Users, Registered Users 2 Posts: 2,115 ✭✭✭monkeynuz


    HeidiHeidi wrote: »
    Hi, I replied on your other thread, but this one seems to be getting more traction, so.....


    If you want to get rid of the algae spots/staining, I can recommend Algon - I got it in my garden centre, spray it on and leave it to dry in (perfect weather at the moment) and it works over a few days. If the problem is bad, I would guess that a few repeated applications might be needed.


    As regards restoring the colour - I really don't see how bleach or chemicals or power washing would do that? I would really love to get the colour back into mine as well, so hoping that someone comes along with a suggestion!


    But I think there's two separate problems here......

    Hypochlorite will clean and "restore" the colour, basically it takes the years of staining and discolouration away.

    I had avoided doing it for some time as I was rather sceptical about doing it but when I finally did, I only wished I'd done it years ago.


  • Registered Users, Registered Users 2 Posts: 639 ✭✭✭JMR


    Wanted to follow up on this as I treated the patio with sodium hypochlorite and pressure washed.

    I bought 5L of sodium hypochlorite and initially used it a dilution of 3:1, however this didn't provide great results.
    I treated again with a more concentrated solution and, while far from new looking, it's a lot better than it was.
    Before and after pic attached


  • Registered Users, Registered Users 2 Posts: 2,115 ✭✭✭monkeynuz


    JMR wrote: »
    Wanted to follow up on this as I treated the patio with sodium hypochlorite and pressure washed.

    I bought 5L of sodium hypochlorite and initially used it a dilution of 3:1, however this didn't provide great results.
    I treated again with a more concentrated solution and, while far from new looking, it's a lot better than it was.
    Before and after pic attached

    With regards the black spotting, give it another go and dwell on the black spots with the pressure washer for longer.


  • Registered Users, Registered Users 2 Posts: 6,916 ✭✭✭Alkers


    Does the same advice work for the black sandstone?


  • Registered Users, Registered Users 2 Posts: 2,115 ✭✭✭monkeynuz


    Alkers wrote: »
    Does the same advice work for the black sandstone?

    Yes


  • Posts: 14,266 ✭✭✭✭ [Deleted User]


    Can anyone explain to me how it's bringing back the colour?

    My uninformed thought process would have been that direct sunlight would have faded the patio over time, and it'd need to have a 'dye' of sorts applied to colour it again?


  • Registered Users, Registered Users 2 Posts: 31,006 ✭✭✭✭HeidiHeidi


    Can anyone explain to me how it's bringing back the colour?

    My uninformed thought process would have been that direct sunlight would have faded the patio over time, and it'd need to have a 'dye' of sorts applied to colour it again?
    I would like to know this too!


    From what I can see, what the OP applied is basically a solution of bleach - how on earth that restores colour in stone is beyond me.


    I'm not denying that the stones look far better in the right-hand (I'm assuming that's the "after") picture though.....


  • Registered Users, Registered Users 2 Posts: 21,531 ✭✭✭✭Alun


    Can anyone explain to me how it's bringing back the colour?

    My uninformed thought process would have been that direct sunlight would have faded the patio over time, and it'd need to have a 'dye' of sorts applied to colour it again?
    Indian sandstone is naturally that pink / yellow colour, but over time it gets dirty that's all. The black dots are lichens. They can penetrate into the surface of the stone which is why they're so difficult to remove especially if you leave it too long. If you clean regualarly from the start they won't get a foothold, as it were and are easier to remove.


  • Registered Users, Registered Users 2 Posts: 251 ✭✭Frank11


    JMR wrote: »
    Wanted to follow up on this as I treated the patio with sodium hypochlorite and pressure washed.

    I notice the runoff from your stones is to grass. I was worried the bleach/chemical stuff would be damaging to the grass.
    Have you noticed any damage?


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  • Registered Users, Registered Users 2 Posts: 2,115 ✭✭✭monkeynuz


    Frank11 wrote: »
    I notice the runoff from your stones is to grass. I was worried the bleach/chemical stuff would be damaging to the grass.
    Have you noticed any damage?

    It will bleach grass if left but if you are careful you can avoid spraying the grass or wet the grass first with water.

    When rinsing the paving you are diluting the solution sufficiently to avoid any discolouration of the grass.


  • Registered Users, Registered Users 2 Posts: 639 ✭✭✭JMR


    Frank11 wrote: »
    I notice the runoff from your stones is to grass. I was worried the bleach/chemical stuff would be damaging to the grass.
    Have you noticed any damage?

    No damage to the grass, it's fine.
    As another poster mentioned, washing it off afterwards dilutes the solution to a relatively harmless level


  • Registered Users, Registered Users 2 Posts: 6,916 ✭✭✭Alkers


    IS this stuff available to order / collect anywhere at the moment?


  • Registered Users, Registered Users 2 Posts: 639 ✭✭✭JMR


    Alkers wrote: »
    IS this stuff available to order / collect anywhere at the moment?

    I bought from this guy
    http://www.doc-solder.ie/store/

    Collected in Dublin 11


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