Removal of rig brick?

I have that phony vrick on my wall on a house I bought. I used a chisel to remove all of the misrepresent brick but there is adjectives this black stuff under it. How do I achieve that off? Is this of late a piece of plywood on the wall or is it more extensive than that? Thanks in finance
Answers:    Sorry, but l did that at My home, and had to own it all re plastered, l expect that had to come past its sell-by date first, try removing a small piece.
I run into this a lot it could two things. In most cases the black stuff is of late "mastic" it is a type of glue used to attach the brick to the wall adjectives you will need to do is rub it off, do some plaster work, sand, and paint. This is what it in general is however I have see a few times where at hand will be a backer board beneath the mastic if that is the skin you have to remove the underwriter board and put in some sheet rock. I will let somebody know you that on some of the remodels I have done it is easier to cut that nouns out and put in spanking new sheet rock that depend on the size of area and how much refinishing will necessitate to done if the mastic is scraped off. I hope this assist but if this is a large nouns I would look at putting up new sheet rock.