Is it possible to clean it with low pressure, without a lift, with SH + oxalic acid + cold water?
Why oxalic? I don’t think it’s possible. All limestone I’ve cleaned requires a strong sh mix followed by medium pressure. @racer?
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Probably thinking oxalic for any rust staining.
neutralize?
I thought that’s necessary to prevent orange discolour…
I ve never done limestone though. Just leaned the thoery.
It’s gonna be hard to apply any pressure at that height…
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I would also think about all that glass. Over spray would spot or streak it. Just a thought
Is there anything else I should be aware of except extra rinse work?
Dunno. Never cleaned anything like that. Hopefully one of the more experienced guys will chime in. Consider what @anon37135677 said about needing some pressure to clean it and how you will accomplish that.
Chris is right. On some limestone you’ll need Oxalic to neutralize the SH. Not all, depends on where it comes from. Some has a lot of iron in it,and it’ll leave it kind of orangish in color if you don’t. This building doesn’t look like it has much, if any, so may be ok not using.
You can softwash with your 12v or whatever, going to take several coats probably on the bad places and probably at least some pressure, like with a shooter tip. Just prewet windows and don’t let mix come close to drying on those frames.
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Thank you for the confidence boost, Rick.
One question, is hot water necessary? I don’t have a heater. Should I wait till it’s warmer to do this job?
You can try a spot and see. You can do it w/o heater, just a little harder
Thanks, Rick. You are always amazing 
Bookmarked! As always great advice Racer.
