Hi folks. I was asked to weigh in on this thread a while back so I apologize for the delay but the wide range of topics required some sort of organizing my response. As I see it there seem to be several concerns and I think that I’ll address them in increasing complexity so ya’ll can bail out when I start sounding like a martian.
So first off ceramics is a field that has a fairly high capital outlay and embodied energy cost, which is fine if this is your business but maybe not quite as practical for a project or two. Add this to the rather specialized skillsets needed to make pots or tiles and you’re probably better off getting them elsewhere for a better ROI (most novices find it hard enough to make something over three inches and keep it roundish). That being said anyone interested in ceramics should give it a go but just be aware that you may be more in the having fun category and it probably will cost more than you could ever save, but if you have fun it’s not my place to say how you spend your money.
As for the durability of wares in low fire… they just aren’t and quite frankly anyone who thinks something fired at 1300 F is vitreous either doesn’t know the what vitrification is or is full of shit.
There are three ranges (broadly speaking) that we fire to: low, medium, and high fire. Vitrification is directly related to body maturity and therefore absorption rates, earthenware will have 5-15% absorption, stonewares 0.5-1.5% and porcelains less than 0.5%. As you fire hotter you get more vitrification. This isn’t to say that there isn’t a long tradition of cooking in low fired wares, cooking a pot does the same thing as cooking food… It kills germs. However those germs won’t stay above the critical 140 degrees for long enough on wares one eats off.
That brings us to testing standards. Unless someone can show you the documentation for acid and alkali(ne) leach testing of lead and cadmium don’t use the piece for food or drink. This testing should be at the cone it’s typically fired to as well as one cone up and down to ensure safety within a margin of temperature fluctuation. Technically there are ppm standards for both of these materials, however both will bioaccumulate as the body has difficulty dealing with inorganic compounds that aren’t needed. Crazing is the crackling pattern seen on some wares… It should be avoided on any food contact surface that is not on vitreous clay as the cracks go all the way to the clay body and if it is porous it will absorb material.
Microwave safety is mostly subjective with the exception of metallic lustre type finishes, depending on the user's tolerance for heat. Once again performance in regard to the heat transferred to a mug handle will improve (less heat felt in grabbing handle) as vitrification increases with higher firings. Use a potholder and you’ll likely have no problem here.
Few potters indeed, actually test their wares but most will tell you that it’s microwave and food safe, combine this with a tendency of potters to use glaze recipes they have found without knowing how to test or correct for faults and you have a tricky ricky situation.
In practical terms, anyone with enough interest can take up and do just about anything to a certain skill level. But there will always be an associated cost to learning.
