Dave Osborne wrote:
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.

Well if its limestomne why call it sandstone?

Indian sandstone is sandstone. AKA fake York stone. IIRC