Hi
I just rang the tile shop here in Sydney Australia called CTM its a large tile market chain. Its where I bought my adhesive from and explained that you live in the USA. He said there are two ways you can do it. The first way, which is the way I did it is with a product called Optima which sticks straight on the old tiles or the other way is you use a product called Prebond. What you do is paint this on the old tiles let it dry then you can tile over it with normal tile adhesive. But the problem is, he thinks you can't by these brands in the USA. But he is very confident you can get the same type of stuff where you come from. Also you can do a web search by just typing in (tile adhesive) loads and loads of info comes back. Please let me know how you go. Regards Noelene