Tim T Posted March 9 Report Share Posted March 9 Apologies for this totally non car related question! I have a list of jobs to complete before I can get back on my 5 project (so I am told!) The biggest is properly cleaning all the black spot off 80sq metres of Indian sandstone patio! Can anybody please recommend either a really good branded product or preferably an off the shelf chemical to spray/brush on and then pressure wash off. One suggestion that I have had is sodium hypochlorite ???? Be really grateful for any experiences please. Many thanks Tim Quote Link to post Share on other sites
PodOne Posted March 10 Report Share Posted March 10 Lots of watery bleach a soft sweeping brush followed by a pressure washer fitted with a rotary deck/patio brush will do a good job. Works a treat on my block paving and deck. Mine needs doing again after a few years but I'm keeping quite ! Quote Link to post Share on other sites
Charlie D Posted March 10 Report Share Posted March 10 Just be careful with whatever chemical you use. A friend used diluted bleach and washed it all away off the patio onto one of his flowerbeds. Result was brown flowers. Quote Link to post Share on other sites
Kiwifrog Posted March 10 Report Share Posted March 10 I have used a vinegar/salt mix to remove mold stains from the walls of my house Quote Link to post Share on other sites
cvtrian Posted March 10 Report Share Posted March 10 I have used sodium hypochlorite many times on my block paving and patio slabs, which is sold as milking parlour disinfectant and swimming pool disinfectant, after a pressure wash with a rotary head. Great results. As with any chemical, wear protective gear, particularly eye protection and avoid getting it on you or your clothes, and it will kill anything in your flower beds. It's usually available in 15% strength, which I further dilute X3 down to 5% - in order to dilute, always add the solution to water and never the other way around. e bay usually around £25 for 10 litres @15%. Patio Magic is also very good, but more expensive @ ~£20 for 5 litres Good luck Quote Link to post Share on other sites
stillp Posted March 10 Report Share Posted March 10 Washing soda, according to morning TV: https://www.leicestermercury.co.uk/whats-on/shopping/cleaning-expert-shares-easy-trick-9145413?int_source=nba Personally I wouldn't use a pressure washer on the patio as it'll roughen the surface so it gets dirty quicker. Pete Quote Link to post Share on other sites
Rod1883 Posted March 10 Report Share Posted March 10 As Pete says, I wouldn't use a pressure washer on the patio either - you risk blasting all the pointing/resin/sand between the slabs away Quote Link to post Share on other sites
Dave Burgess Posted March 11 Report Share Posted March 11 This works very well, I've used it many times. It lasts for several years before the green stuff starts to grow back. It works on patios, fences garden sheds etc, anywhere that goes green. Dave Quote Link to post Share on other sites
Tim T Posted March 11 Author Report Share Posted March 11 Many thanks for all the various views, all very valid points. Grouting is 100% sound so am happy to pressure wash albeit with a slight risk. Have tried Patio Magic before and it made no impression at all. Karcher patio disc brush thing is ok but my slabs may have been neglected for too long and therefore need a more aggressive approach. Will test chemical actions but ensure keeping it off any greenery. Many thanks, Tim Quote Link to post Share on other sites
Nigel Triumph Posted March 11 Report Share Posted March 11 I've recently used a Kärcher pressure washer on two areas of long neglected Indian limestone patio. It took a while but the slabs came up very well. The grout was already failing and much of it was washed out while cleaning the slabs. All moss and algae were removed by the pressure washing but some black organic spots remain, though I feel that adds to the character of the patio. Before cleaning, the patio was dangerously slippery when wet, and coated the soles of my shoes with dirty green gunk. It's now safe to walk on and the door mat isn't getting covered in algal slime! Nigel Quote Link to post Share on other sites
Tim T Posted March 11 Author Report Share Posted March 11 57 minutes ago, Nigel Triumph said: I've recently used a Kärcher pressure washer on two areas of long neglected Indian limestone patio. It took a while but the slabs came up very well. The grout was already failing and much of it was washed out while cleaning the slabs. All moss and algae were removed by the pressure washing but some black organic spots remain, though I feel that adds to the character of the patio. Before cleaning, the patio was dangerously slippery when wet, and coated the soles of my shoes with dirty green gunk. It's now safe to walk on and the door mat isn't getting covered in algal slime! Nigel Reckon that we have the same patio Nigel! Was hoping to get rid of the black spot and then seal. Will put an unmanipulated photo up tomorrow. Tim Quote Link to post Share on other sites
Tim T Posted March 12 Author Report Share Posted March 12 Here you are Nigel. Cleans the gunk off very well with the pressure washer, but leaves the black spot. SWMBO doesn't but the patination pitch . Interesting how some stones have virtually no black spots. Cheers, Tim Quote Link to post Share on other sites
RogerH Posted March 12 Report Share Posted March 12 1 minute ago, Tim T said: Here you are Nigel. Cleans the gunk off very well with the pressure washer, but leaves the black spot. SWMBO doesn't but the patination pitch . Interesting how some stones have virtually no black spots. Cheers, Tim AArrr - the Black Spot Roger Quote Link to post Share on other sites
Tim T Posted March 12 Author Report Share Posted March 12 1 hour ago, RogerH said: AArrr - the Black Spot Roger … Jim lad! Quote Link to post Share on other sites
CarreyRT Posted March 15 Report Share Posted March 15 On 3/10/2024 at 8:45 PM, Kiwifrog said: I have used a vinegar/salt mix to remove mold stains from the walls of my house We've been using this mix as well with good results. Quote Link to post Share on other sites
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