I have ceramic tile on a cement slab foundation. Some of the tiles have become loose and I have removed them. I want to reinstall the tiles, but there is mastic stuck to the back of the tile. Any idea how to remove this without cracking the tiles? I have 8-10 tiles to reinstall. Thanks!

Well, here I go again. Check out the Fein Multimaster at Fein Power Tools USA Quality Precision Power Tools. The videos are convincing. Warning, it's pricey. There are two scraper blades available, one is hard and the other flexible. It removes material by oscillating up to 20,0000 osc/min. It will work for you.

Ptandatx - What I have used several times is a propane toruch and a wide putty knife, I would run the flame over the back side to heat the addhesive and take the putty knife and easly scrape across the piece of tile. I found that is a lot safer then anything else. I hope I have helped you with your problem, If I have rate my answer below ::: Good luck & GOD BLESS ::: F.B.E.