Softwash on this textured render today - really course surface. Wet it up, then washed it initially with 4% SH using 40 degree fine fan jet nozzle to get as much mix into the little crevices as possible. Used quite a lot of mix. Then hit the ledge stains with a high concentrated mix. Didn’t rinse much due to texture and weather was perfect so it wasn’t drying out quickly, so I just repeated another few layers of 6% SH. Red algae flared and disappeared after a while, and most of the other algae staining is all but gone. The stains under window sill ledges seem immovable. I used a decently strong fresh mix of oxalic acid sprayed on with garden sprayer next on them but obv not rust as I didn’t notice any change after leavening to dwell and rinsing thoroughly. I lastly applied a neat hypo mix to them and left tonight hoping they work away over night. Personally given that they’ve hardly changed since I started the job. Any ideas on how to remove them ? I mean I thought of a specialist gel product that screw softwash manufacturers sell but given they’ve hardly changed at all I don’t hold out much hope. Maybe the water has etched the render or something weird ? Any pros got an idea on this one thanks ?
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Course render softwash
- Thread starter DeLaCruz
- Start date
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I've always had problems with staining on the edges of window sills it actually drives me nuts when the rest of the house looks nice. There are far more qualified people on here that might be able to help, I normally use the pressure washer (turned down) to attack the edges which the stains won't go despite putting on neat hypo.
I don't normally reapply anything until a few days or even a week has gone by to let it fully dry out and see what it's like afterwards. If the job is close I tell the customer I'll be back to check the work over and apply more once it's dried out, they are always happy with the efforts I make.
Sorry, not much help.
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I think @kevinc250 recommends using household bleach on moustaches. Hopefully he'll see this
isn't that just watered down hypo though?
interesting.. Would be interested to know if this works, though if hypo doesn't get it off I'll be amazed if household bleach does?
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Not a clue that's why I tagged him in
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I think household bleach contains sodium hydroxide as well , I have tried this but not found it to remove the marks either .
IIs it definitely not red algae? Because there can be multiple layers of it and it goes through several colour changes.
Others will know far more about this than me, and I may be wrong, but I'd be wary about jumpong from hypo to oxalic then back to neat hypo. It's an interesting concoction.
And if it was rust, hypo isn't going to do you any favours.. Was there any colour change to purple with the oxalic? Each to their own but I like to have an understanding of what I'm dealing with before throwing chemicals at it.
They're great for the purposes they're designed for but there's always potential for disaster.
Yeah I’ve used oxalic and hypo lots of times previously - with the oxalic even if it doesn’t remove the rust stain (the really stubborn ones for example) I always see a change in the staining - water runs off with tints of the rust in it. On this one literally not a single thing changed and rinse off water had zero tinting in it. Fwiw I rinse and rinse again using the pressure washer to make sure it’s as rinsed off and diluted as possible before I do any further treatments.
