Hello, we have a house built in 1949 and sometime probably in the 70s, the then-owner furnished the basement. One of the rooms in the basement was furnished with styrofoam which we began to tear out.
At first, we thought that where the walls were black were moisture damages, but in some places, it almost looks painted onto the concrete. (see image) We are considering sending in samples but does anyone have experience with this or can tell from the images if it is black glue or not, and do you have any companies you can recommend for sampling?
/ Max