I dont think people are getting his point here ?
He's asking what adhesive to tile porcelain tiles on top of existing Ceramics, Flexible adhesive is not good enough!
I am in the same boat next week and still not quite sure what road to take?
Ardex do a brilliant Primer P4 dries like rough sandpaper on glazed tile ,but is £70 trade at CTD
I reckon my other option is an admix to rapid set ,much stronger bond than Flexible addys!