I can't really answer your question for sure (just a layman's guess) - but I am keen to use Iznik tiles myself in a similar way.

I guess that you would have to know whether the tiles had been fired after painting, and also whether they have been sealed with a layer of varnish?

Genuine Iznik tiles are quite expensive, as I'm sure you'll know! What about trying to get some replicas that would have been mass produced, and not so much of a risk?

I don't know where you're based, but I'd be interested to know where you got your tiles? I am in the UK and have not found any at a reasonable price, so I am going to buy some in Turkey on my next trip.

If you are unsure about whether the tiles will be ok, you could try buying a ready made fountain. I have found some Morroccan fountains that I like. Not authentically Turkish or Iznik, but depends on whether it must be Iznik or not?

Try this

http://www.moro…

I am tempted by these!