I have removed old 9x9 tile from my basement floor can I lay porcelain tile over the mastic or do I need to use a disolving solvent? Also will the moisture because it's a basement effect the tile sticking? Thanks... blmgreek

What type of tile was the old tile, vinyl? You should remove all of the old mastic with a floor scrapper. I have even used a 4 in. razor scrapper when the mastic was still too soft to chip. You should check the concrete floor for moisture. Clean a 12 x 12 area and tape down clear plastic. Tomorrow you should not see moisture droplets inside the plastic.

The tile was 2% asbestos type, the black stuff left on the floor is is hard like it was painted on the floor.

If the tile is old enough to have asbestos in it then the mastic may too. I am not an alarmist but I don't like to work with asbestos. It may be a good idea to get a test kit from the hardware store and test the glue.

Tile over it with modified thin set get r done:)