I have a small 2br on slab 1950’s originally had 9” vinyl tiles and dark brown/ black adhesive. After the tiles were removed the abaters softened/dissolved the glue and mopped and wiped up what they could. I scrub brushed and mopped to clear. The slab is discolored and retains imprints in the original tile layout. Clearly there remains some residue. I’m planning on 12x24 porcelain with large format thin set med body. I’m concerned of course for the adhesion. Should I put a sealer on next.