I am repairing a 50's bathroom and removed a bunch of tiles that were coming off the shower wall. I have spent inordinate amounts of time with hammer and chisel to get most of the old cement removed from the backs of the tiles. I am now ready to try and reinstall them.
I want to remove some of the loose cement that they were attached to and replace it. This was an area where the tub met the tile wall and water invaded behind the tile. The old cement is spalling and loose and someone at some point tried to deal with the problem using contact cement. I would love to be able to replace the cement substrate but cutting a one inch piece of backer board and filling it gives me pause. Can I mix up backer cement like the old school stuff that's there now? What type of mix should I be using to create the backing that I can tile to?
You can see pictures here:
The lower part of the first picture will give you an idea of what I'm trying to repair (simply click on picture to enlarge).