I am planning to put natural slate tile on concrete slab floor in the house. I removed the original 1957 9"x9"vinyl tiles and I am left with traces of the original black glue everywhere. The question is... Can I lay the new slate tiles(using standard adhesive thin set) directly over the concrete covered with this old black glue? The area is approx. 70sf and I am trying to avoid grinding the glue off the concrete or using an adhesive chemical remover.
Thanks, Paul C.