do random checks if the back of the tiles are fully covered with tile adhesive. Check if tile adhesive mortar stilladheres to your finger to find out if the open time has not lapsed, if open time has lapsed, remove old tile adhesive layer and reapply a newone toavoid bonding failure. Never add newly prepared tile adhesive to a previously mixed batch, use tile spacers for uniform grout lines, a tile joint width is needed to accommodate possible tile movement due to thermal deformation, substrate shrinkage or tile expansion, thus preventing,