Black mould spots again
I've asked this question before on this group, but having tried people's
suggestions without success I thought it was worth another go. I have very unsightly black mould spots on the concrete slabs on my patio and garden path. An ordinary scrubbing brush has no effect, a lot of hard brushing with a wire brush has limited effect but has now started ruining the surface of the concrete (without really bringing off the mould) so I daren't do it any more. Chemicals I've tried without success include algae removing patio cleaner, jayes fluid (including neat), bleach (potassium hydroxide type and sodium hypochlorite type - including neat), sodium hydroxide, and a sodium dichlorophen fungicide. Any other ideas I could try? Anyone who would like to suggest that brushing sand into it would work where wire-brushing the surface of the concrete off has failed is welcome to come round and try it. |
Black mould spots again
"Ben" wrote in message ... I've asked this question before on this group, but having tried people's suggestions without success I thought it was worth another go. I have very unsightly black mould spots on the concrete slabs on my patio and garden path. An ordinary scrubbing brush has no effect, a lot of hard brushing with a wire brush has limited effect but has now started ruining the surface of the concrete (without really bringing off the mould) so I daren't do it any more. Chemicals I've tried without success include algae removing patio cleaner, jayes fluid (including neat), bleach (potassium hydroxide type and sodium hypochlorite type - including neat), sodium hydroxide, and a sodium dichlorophen fungicide. Any other ideas I could try? Anyone who would like to suggest that brushing sand into it would work where wire-brushing the surface of the concrete off has failed is welcome to come round and try it. Pressure washers are good for cleaning concrete. IMHO they are certainly more effective than wire brushing. They do tend to lift anything loose, but they bring concrete slabs up like (almost) new. Perhaps it isn't mould, but just general filth settling in to the fine holes in the surface of the concrete. I find our slabs go grimy over the year, but a good blast with the pressure washer makes them much cleaner. HTH Dave R |
Black mould spots again
David W.E. Roberts wrote:
Pressure washers are good for cleaning concrete. IMHO they are certainly more effective than wire brushing. They do tend to lift anything loose, but they bring concrete slabs up like (almost) new. Perhaps it isn't mould, but just general filth settling in to the fine holes in the surface of the concrete. I find our slabs go grimy over the year, but a good blast with the pressure washer makes them much cleaner. It definitely isn't just general filth. On otherwise spotlessly clean slabs there are black circles about the size of a pea on average that stand up slightly above the surface as if black paint has been spilled. On one of the slabs some coloured paint has been spilled at some point and it gives a very similar effect. I had resisted using a pressure washer as the patio is just layed straight onto sand with sand between the slabs and I didn't want to blast the stuff away, but I guess I'm going to have to give it a try. |
Black mould spots again
We have the same black mould problem on both patio and stone walls
...........however no amount of pressure washing shifts them ........do not know what chemical to resort to but sure as hell they need dealing with next spring ........maybe if i do get them clean i need to seal them all with Thompsons or something "David W.E. Roberts" wrote in message ... "Ben" wrote in message ... I've asked this question before on this group, but having tried people's suggestions without success I thought it was worth another go. I have very unsightly black mould spots on the concrete slabs on my patio and garden path. An ordinary scrubbing brush has no effect, a lot of hard brushing with a wire brush has limited effect but has now started ruining the surface of the concrete (without really bringing off the mould) so I daren't do it any more. Chemicals I've tried without success include algae removing patio cleaner, jayes fluid (including neat), bleach (potassium hydroxide type and sodium hypochlorite type - including neat), sodium hydroxide, and a sodium dichlorophen fungicide. Any other ideas I could try? Anyone who would like to suggest that brushing sand into it would work where wire-brushing the surface of the concrete off has failed is welcome to come round and try it. Pressure washers are good for cleaning concrete. IMHO they are certainly more effective than wire brushing. They do tend to lift anything loose, but they bring concrete slabs up like (almost) new. Perhaps it isn't mould, but just general filth settling in to the fine holes in the surface of the concrete. I find our slabs go grimy over the year, but a good blast with the pressure washer makes them much cleaner. HTH Dave R |
Black mould spots again
You could try phosphoric acid, aka known as brick acid, for cleaning
efflorescence off brick. It theoretically should remove a certain amount of the surface so should bring it up like new. All entirely at your own risk though, Andy. "bnd777" wrote in message ... We have the same black mould problem on both patio and stone walls ..........however no amount of pressure washing shifts them ........do not know what chemical to resort to but sure as hell they need dealing with next spring ........maybe if i do get them clean i need to seal them all with Thompsons or something "David W.E. Roberts" wrote in message ... "Ben" wrote in message ... I've asked this question before on this group, but having tried people's suggestions without success I thought it was worth another go. I have very unsightly black mould spots on the concrete slabs on my patio and garden path. An ordinary scrubbing brush has no effect, a lot of hard brushing with a wire brush has limited effect but has now started ruining the surface of the concrete (without really bringing off the mould) so I daren't do it any more. Chemicals I've tried without success include algae removing patio cleaner, jayes fluid (including neat), bleach (potassium hydroxide type and sodium hypochlorite type - including neat), sodium hydroxide, and a sodium dichlorophen fungicide. Any other ideas I could try? Anyone who would like to suggest that brushing sand into it would work where wire-brushing the surface of the concrete off has failed is welcome to come round and try it. Pressure washers are good for cleaning concrete. IMHO they are certainly more effective than wire brushing. They do tend to lift anything loose, but they bring concrete slabs up like (almost) new. Perhaps it isn't mould, but just general filth settling in to the fine holes in the surface of the concrete. I find our slabs go grimy over the year, but a good blast with the pressure washer makes them much cleaner. HTH Dave R |
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