It is pretty easy to get; just Google it for the nearest place to you. Mine came from Jo-Ann's.com but I had a poor shopping experience with them, hence my not recommending my source.
This is one coat of the glaze drying. It didn't seem to make the ink run though you could matte spray coat it first with a fixative if you were concerned. It smells a little like nail polish but washed out of the brush with water so I assume it is acrylic and/or water soluble. There are no brush cleaning instructions. It took about ten minutes for me to be able to handle it OK - I imagine longer would be better - as I said, I am not patient.
It gave a good glaze, pretty clear and with a little profile so it does look quite like tiles. As with all these things it would work really well at 1/12th but it is acceptable if you really can't bear to be doing three coats to get here. The imperfections around the edge of the glass (it is actual mirror glass) are nothing to do with me. I presume it comes from cutting mirror pieces that small (?). It adds to the 'rustic' charm. This mirror will be in Lucien and Matilde's apartment - bought on holiday in Spain.