Sandstone block discolouration

[Healthking]

Hello
I have a few blocks on my extension that have become discoloured. I thought it was maybe due to the wet weather over last winter but despite very hot weather they haven’t improved. When I test them with a damp meter they are reading as ‘normal’. I tried using the power hose on them and I have even resorted to a wire brush but to no improvement. I coated the wall with Stormdry to see if that would help but that has just made them worse. Any advice on how I can get them back to sandstone colour? These particular blocks apparently are no longer manufactured

 

[Deluks]

It's a natural product, it will never look completely uniform. Your time is better spent redoing the pointing.

 

[^woody^]

Looks like you have staining from water running down that frame. That needs to be remedied else any cleaning will be in vain.

Jet washing and a non-acidic additive cleaner tends to work, or look at a TORC system which uses water and granite dust under pressure. However, your stormdry treatment may have sealed the surface

You may want a specialist firm, as you probably don't want a shiny new cleaned stone amongst surrounding dirty sones.