I just never had any luck with it and at the time I was using allot of RO to keep my PH down to 7.4 and when I introduced the NEW TC pots stamped Italy my PH went up overnight to 8 and it wasn't until I switched to plastic imitation That I regained control of my PH. Obviously this had allot to do with your water chemistry in the first place. As far as Mexican TC and unfired poetry from there in general, I have literally seen the lead leach into silver metal film when they got wet or heated, but that was 22 years ago, obviously things have improved right.