My old cottage has a wood stove in a corner. The walls behind the stove are brick up to about four feet high. Above the brick is a black material that looks sort of like drywall, but is much harder to the touch, and has texture to it that looks like interwoven threads. I'm assuming this is some type of fire resistant material. The rest of the house is not insulated or drywalled, so I'm pretty sure this one section must be there for fire resistance. My question is: can I paint this material and / or the brick without negatively affecting fire resistance? If so, is there a special paint I should use?