It needs to be about 1/8th an inch for translucency, which is a bit less than a cm, though you could probably get to 3/16ths. If throwing, plan on trimming to get that thin.
Casting is also a beautiful option.
1/8" is a lot less than a cm.
1cm = 10mm
1/8" = 3mm
Yes, I know. That is why I wrote this. I wonder if anyone who thinks porcelain is translucent at a centimeter has actually seen it, because I haven't.