Graffiti Blasters in Chicago uses a high pressure baking soda mixture on unpainted brick.
don’t they clean excess mortar off brick with acid?
dunno…maybe it works.
Agreed. When I worked at BellSouth our crossboxes would constantly get vandalized by some thug and his spray can. We carried Goof Off (or something very similiar), sprayed it on and it dissolved the paint in a few minutes. It turned it into a liquid that could be washed of very easily. Somehow it never seemed to bother the paint that the crossbox was painted in. I never used it on brick, but I would bet that a good coating of it followed up by a low pressure spray of water would do the trick.
So OpalCat, what did you end up doing?