Uh oh! My first attempt at putting tile on a bathroom wall and I may have a problem. Here is the story. I installed Hardibacker board around the tub and green board in the rest of the bath. I taped the seams and used joint compound, then sanded (several times). It looked so good that I taped the seams and corners of the Hardibacker board in the tub area, then used joint compound to smooth everything out.

Here is the (BIG) question. Will I have trouble using thinset (and then putting up tile) on the joint compound? Can the heat generated while taking a shower have any adverse effects on that joint compound behind the shower walls? Should I forget about it and tile the walls? Oh, so many decisions... and being a complete novice, they are all big decisions.

Also, Lowe's sells Thinset premixed in a tub, but also sells some powder thinset that can be mixed with some Flex liquid stuff. (Did I lose any of you with my technical descriptions?? ) Any recommendations would be most welcome.

Thanks for taking the time to help me with this (what seems like a neverending) project. I am having a great time learning, but sure would like to be a bit more confident about the decisions I have to make. Thanks again!

I would talk to someone at Home Depot of Lowe's about tile mastic. It is easier to use and I think it holds better.

The hardi only needed to be taped and sealed with the thinset you would be using to stick the tile. There is a possibility the tile will not adhere fully to the joint compound.

If you were to get moisture behind the tiles, the tiles could become loose.
You can prime the surface of the joint compound and then stick the tiles.

You can use premix thinset if rated for wet areas. I used Mapei brand premix and it works well. Read the directions for the trowel size in regard to the tile size.

Can I install wall tile over sheetrock in my bathroom or do I need to install some type of hardbroad?

Tile mastic is definitely not for this application and as skiberger points out the joint compund was a big mistake. Your seams should have been taped and mudded with modified thinset. Regular thinset is not for walls, modified thinset has an acrylic base that works best on none concrete surfaces. If your tile is not in place yet you should scrape out all joint compound, this stuff will never be waterproof.
Taf, please start your own post/question by clicking ASK. When you jump onto someone else's question it confuses the issue.

I would actually go to http://www.glasstilewarehouse.com. I recently redid my bathroom and was recommended to site by a friend and I am really glad I used it.

I actually just finished up my <a href="http://www.glasstilewarehouse.com/">glass tile bathrooms</a> and I am really happy with the way it turned out