I am renovating y bathroom and I want to tile the shower ceiling a friend has said not to use thinset for the ceiling tile but to use tile glue for this application I want to know if this is a good idea

You can use acrylic modified thinset, it has a very gluey consistency. Tile adhesive would porobably work fine. Are you installing a backer board like Wonderboard or Hardiebacker, you'll need 1/2".

hia ballenger, I too have the same question as to what is best to use and where.. I purchased a 50lb.bag of laticrete thinset mortar for 14 bucks , it is a one step polymer fortified tile adhesive for both interior and exterior applications.. says it is ideal for both plywood and concrete.. (hardibacker or cement board) The funny thing I just heard from my brother who did a few bath projects and through his research.. said, regular thinset mortar is all I need especially indoors.. and that the mastic premixed glue in the 3 gal tub for 30 bucks is not as good according to his research and talking to other pros in the field. I honestly still have a question mark about this?. I am also doing an upstairs shower tub ceiling and in need of two 3x5 sheets of hardibacker.. I wanted to know if EZ grid 3/8 would suffice on a 3'x5' ceiling or should I use the 1/2 hardibacker instead? Also want to know what you would use for the ceiling as for trowel knotch size for 6x6 tile and would use mastic glue instead of thinset mortar thanks!