| Gunguy,
If you can see the chalk lines after spreading thinset mortar over it, you are doing it wrong. You're supposed to first "burn" thinset to the floor using the flat side of the trowel, then apply more thinset and spread with the notched side.
It should be done as described by Johnny, thinset right up to it, not over it.
I would never put chalk lines or start tiling in the center of a room. Ceramic tile on floors is not done that way.
Jaz |