Parents had a gutter that was leaking for some time. That's now sorted, but it has left behind some unsightly white staining on the brickwork below. A scrubbing brush and soapy water has failed to shift it. Any ideas what it is exactly, and how best to clean it up? Photo attached.
Removing white patches from exterior wall
Brick acid , it’s limescale from water .
Ah! I'm sure I was offered that in a nightclub once. 
Thank you - I'll look out for some of that then (muriatic acid according to the internet - hadn't heard that name but I gather it's hydrochloric acid, so will be taking care with that one!).
Thank you - I'll look out for some of that then (muriatic acid according to the internet - hadn't heard that name but I gather it's hydrochloric acid, so will be taking care with that one!).