I would like to know what I should do to tile over the old linoleum tile adhesive (thin black, tarry looking stuff), short of removing it. In one small bathroom I have tried covering it with 2 coats of KILZ sealer. I'm not sure that the thinset will adhere to the KILZ and want some help before I make any (more?) mistakes! In searching other online forums I have seen recommendations to remove the adhesive, and recommendations to leave it in place. My preference is to seal it instead of removing it, since it may contain asbestos.