Myeah, anhydrite is a bit troublesome to tile onto using cementious adhesives. I find that a major problem is that it's got to be completely dry before anything goes onto it, and that's a bit hard to achieve most of the time, especially on new builds. Fortunatly for me and other tilers in Sweden, anhydrite isn't that common over here; afaik, it's mostly only used in office buildings where they use it to level the substrate prior to installing laminate floors and such. Only ever seen anhydrite in a few other places than office buildings.
The few times I've encountered anhydrite I've either ripped it out or gone completely nuts with primer.
Epoxy primer is probably a good idea in some places, but I'd be wary using in places where there is/could be rising damp, as epoxy tends to seal it in.
I've never seen gypsum based adhesives in retail over here. I suspect that if it's at all availible, it has to be ordered in bulk quantities, and then it's only viable for larger corporations that can afford to have their cash locked in stockpiles of materials.
Oyeah, btw, I tried to correct a small error in the post on anhydrite some time ago, but it didn't stick, it seems... I mixed up hydrolysis and hydration in my head when I wrote it. The correct one is hydration. Hydrolysis I the exact opposite of hydration iirc. In case anyone cares that is, or if there's someone here who could use some fancy words to throw in the face of builders who're about to do stupid things
Btw, regarding gypsum based adhesives... How's that when installing, say, travertine? Gypsum adhesives harden through dehydration, don't they? That could cause staining on certain stone. Just a thought.
