First..let me thank everyone who responded to my earlier post about
matching the existing tile. Nothing has been found so I will have to
come up with a pattern in a contrasting style/color.

While taking the old tile up about 12 tiles were broken and need
replacement. To do this I had to take up about 27 tiles. This means that
about 15 tiles can be reused. These old tiles have grout on the edges
and mastic on the bottom side. The mastic appears to be some sort of
clear or light colored plastic.

To the maximum extent possible I intend to reuse the 15 existing tile.
What is the easiest way to remove the old grout and mastic without
damaging the reused tile?

Thanks,

EJ in NJ