What is this stuff?

Not sure if this is efflorescence or mold or ?Anybody ever seen this before?

it looks dirty. or maybe not. who knows.

Hard to tell if the original color was grey or tan. I guess just lift up one and see what color it is underneath.

Original color of brick is a brownish red. The blue/ gray color is what needs to come off. Not sure what it is. It just doesn’t seem like mold or efflorescence. I’ll try a couple different ways to clean and see how it comes out.

Let us know what ends up working. I have something coming up that looks very similar.

That maybe just the color bleached off if it was painted (like cultured stone) and not tinted throughout.