geraldthehamster wrote:
On 10 Sep, 12:04, Dave Osborne wrote:
The parents have had a patio laid in Indian sandstone/limestone. Dad
decided to try getting a few mortar stains off with acid-based patio
cleaner. After a week or so, the patio has turned orangey-brown where
the acid has been.

According to paving expert, the acid staining is permanent. :-(

Anybody know if you can get rid of acid staining? Oxalic acid-based
scouring powder seems to be an option, but paving expert cites oxalic
acid as "unproven". Is it worth a go?

Cheers,
DaveyOz

In how much of a hurry are you? I had some Indian sandstone laid
(always a mistake: if you want a good job done, do it yourself) by a
builder who managed to tread mortar slurry all over the surface, so I
cleaned it off with brick acid, and had just the result you describe.
Two years on, the excess redness has pretty much weathered away.


Thanks for that Richard; it's nice to know it will weather eventually. I
tried the pressure washer this evening and it seems to have dulled it
down a little. Parents' pressure washer is a bit crap tho'. Will try
with a more powerful PW if the Oxalic acid has no effect.

Just to be clear for the pedants, it is in fact limestone, but it is
(apparently) sometimes called Indian sandstone.