There are those who claim that if it ain't white and translucent, it ain't porcelain. While I can see where they are coming from, and while I personally have a soft spot in my head for whiteware, I am nonetheless reluctant to be that restrictive, and in any case I believe that there are other important issues. Here's a shot at an alternative definition:
If it is composed largely or entirely of kaolin, feldspar (or equivalent), and silica, it is almost certainly porcelain. If it is composed almost entirely of clay(s), it almost certainly is not.
(Mind you, this doesn't hold in China, where it is sometimes possible to make 1-ingredient porcelain, depending on where you are. I'm not going to get too far into that here and now, but I understand that the kaolin in some parts of China contains suitable quantities of both silica and a pleasantly plastic form of white mica. Even if that is not entirely accurate, it will have to do for now.)
I have used at least four different commercial throwing porcelains, none of which was the least bit translucent (in my terms, which I'll get to), none of which could be described as "whiteware" except by the remotest stretch of imagination, and none of which was stoneware, either, at least the way I think of stoneware. (The "translucent or nada" people would describe these bodies as "white stoneware".) Here I must confess that most of the stoneware I've thrown was rather heavily grogged, and I tend to think of the stuff as gritty and abrasive even though that's far from necessary. I don't know, for sure, but I suspect that even ungrogged stoneware (by my definition of the term) typically has noticeably higher wet strength and plasticity than porcelain; porcelain, lemme tellya, is creamcheese.
This is not to say that I dislike the commercial stuff; far from it. I am much more comfortable with porcelain (of almost any sort) than I am with stoneware (of almost any sort except maybe B-Mix), partly I think because I started with it, partly because I've had much more practice with it, and partly because I much prefer the feel of "clay" that isn't grogged and doesn't feel like it's ripping the skin off my hands. Not only is it more comfortable, but in addition I find it considerably more sensual, and I like that.
The B-Mix I've dealt with was ungrogged, though I understand that there is a grogged version as well. For those of you who aren't potters, "grog" is bits of gritty stuff that you add to "clay" to make it stronger when it's wet. Grog also adds a certain amount of speckle to the fired product, and many people like that. I like it, sometimes. Many different things can be used as grog. I've watched Robert Fornell use sand that was so coarse it could have served in a pinch as aquarium gravel (it was sharp, too); I was amazed that he still has hands, but he trained in Japan, and he is very good. My guess is that he can throw "clay" with that stuff in it all day and not hurt himself.
(Just for reference, I surrounded the word "clay" with quotation marks
because porcelain is typically 50% or less actual clay; my current
whiteware mix, in fact, is only 35% kaolin, and has no other clay in it
except, for example, when I'm trying half a percent of food-grade
bentonite as an experimental plasticizer. Stoneware, as I point out
above, actually is clay, almost entirely, except for some of
the kinds of grog that get put into it.)
Pseudo-mailto: jon [at] bazilians [put it here] org
Last modified: Mon Jan 29 20:06:32 PST 2001