Reno sting an old house and discovered shiplap under the Sheetrock while doing minor plumbing repair. Removed a square of Sheetrock in another part of the wall and discovered what appeared to be tar paper on the shiplap. I have a photo, but cannot figure out how to post it. I would like to determine if it is tar paper that has “melted” to the wall (this May have been a porch at some point) or if this is asbestos mastic (an adhesive)... and maybe the people who laid the linoleum simply smeared it one the walls while wiping their tools (there are some interesting things in this house). At any rate, I would like to make a determination and either tear out the sheet rock and figure out HOW to remove the tar paper or, IF ASBESTOS, replace my piece of drywall, paint my bathroom, and call it done!