The difference between
china & earthenware

Every clay has a different firing temperature range. Depending upon what kind of clay it is, there is a point at which it is mature, and further heat will ruin it. Ceramists divide clay into two types: low-fire and high-fire. If you think of a thermometer, and think of "zero", the low fire clays basically are heated to temperatures that would be "below zero". That's why they have a "0" in front of the number, it's below the zero on the thermometer. So a cone 04 bisque fire would be like saying "four below zero", and a cone 06 fire would be "six below zero" which is even cooler than four below. See? And the high fire clays: stoneware, bone china, and porcelain, are above zero. They can go up to cone 10, which is the highest cone I can find common reference to. So cone 5 clay is high fire, and cone 05 clay is low fire.

The high fire clays don't just fire hotter, they actually make a "chemical inversion" and become something different during their maturity. Earthenware just gets hotter and hotter, but it is always earthenware. Bone and porcelain actually become vitreous (means they don't absorb water) and before they become hard, they turn almost jelly-like. Before this stage, they would not be mature. That's why bone and porcelain need supports, during firing, and pieces will stick to each other if not separated by a special separator. Keep this in mind... it's important later.

We once had a firing where the kiln sitter failed, and I was too inexperienced to turn the kiln off. I kept adding time to the shutoff timer, hoping that the sitter would shut off. When finally I shut it down, it was a real shame. Owynns (grey owynns) had stilt wires that erupted through their backs, like a blooming flower of melted pottery. Their legs were warped, and their color was an amazing mustard with brown points. You see, the colors that the Owynns were painted with continued to change as the fire got hotter. They were also vitreous, and you couldn't get glaze to stick to them. This is the lesson... know your firing times, and always play it safe. Keep a witness cone where you can see it through a peephole, so that when it bends you can be sure that the firing is done. And, if in doubt, turn the kiln off, let it cool down, and start again with a fresh cone. One failed firing in hundreds, but I lost eight hundred dollars worth of ware that day, and we ate a lot of macaroni and cheese for a long time.

Anyway, bone china and porcelain are different altogether. They are both high-fire, but porcelain has a clay called kaolin and one called pe-tun-se. We call them china clay and china stone, respectively. Bone china was first developed in Europe as a substitute for the Asian porcelain, whose import was killing their domestic market. Bone china actually has ground, calcined animal bone... a lot of it. I forget how much, but think it's darned near half. Porcelain and bone china competed for the same market, and they both have good points and bad points, as far as the production of teapots and plates are concerned. For our purposes, we don't need to really worry about the differences. They are very strong, very white, and require very special handling to cast and fire. The supports are cast at the same time and out of the same clay as the actual piece (well, actually, they can be cast at different times and held in damp boxes, but you know what I mean) so that the whole shebang shrinks together, because otherwise there would be stress on the ware and it would fail.

Earthenware, on the other hand, requires no support generally. Because we are all most interested in horses, we can qualify that and say that we sometimes like to support our ware so that some small warpage will not occur in legs that are thin in proportion to the horse's body. This warpage is just from the weight of the body, and it is so small that you hardly notice most of the time. I have stood up all of the Red Okie Clays for firing, and knowing that warpage wouldn't have been a problem sure would have helped when Suspiro was around! Now remember, we are talking here only about the bisque fire. Stilting for glazing is a whole 'nother discussion.

Because bone and porcelain MUST be stilted, they cannot be painted while in greenware. The stilts would ruin the paint. Because earthenware does not require stilting, or the stilting can be done with a strong wire going up a hole into the body and resting on the back, earthenware can be painted before firing. The paints we use for earthenware can be applied right to the unfired surface, and will become part of the clay surface of the horse. These paints are tinted by oxides and minerals, basically ground up rocks and clay. Black is manganese oxide, blue is cobalt, brown is red iron oxide, etc. They attain their color during the firing, and are affected by the firing temperature. Some cannot go above a certain heat, or they disappear, and some are stable throughout a very long range of heat. Cobalt blue, for instance, is one that is very stable, and that is why it was commonly used for hundreds of years on Asian and European ware, both high and low fire. Reds are the most unstable, as anyone who has tried to achieve "nose pink" can attest. Jim Renaker called the less stable colors "fugitive colors", or those who escape up the chimney. If you fire a brown horse over and over, you continue to lose the brown, and ultimately? Don't know, never tried, but you sure would have a different color in the end.

Because high-fire ware cannot be painted before the firing, generally we see ware that has had a glaze applied, and "over glaze" paints or china paints are used. So the white piece that has been bisque fired is glazed, that is fired, and finally the paints are applied over the glaze. These paints have an oil base, and are sold as powders. You mix them as you use them. Anthony at Alchemy told me that when he started at Royal Worcester, in about 1964, he spent six MONTHS just grinding pigments and learning to mix the paints. Then they let him make brush strokes. (I worship at the altar of the master!!!) He makes it look easy, but it is really very difficult. The first layer of paint must be fired before the next layer is applied, to set it, and successive layers are fired slightly lower each time. This paint fires in the ranges of 016 to 020, or thereabouts, very low and cool, just enough to soften the glaze underneath so that the paints can sink in.

Actually, bone and porcelain can be painted with underglazes in the bisque state, and glazed as we "earthies" always do. Beswicks are in the middle ground, although they are earthenware they are actually painted over the glaze. Hence, always white front legs, where the painter holds the horse. Sometimes you can see the "wipe" marks where the painter wiped excess paint off of the glaze and left smears. See the flow chart in the front of the Beswick or Royal Doulton book, and you will see the little man unloading unpainted bisque...glazing...refiring...painting...refiring. They must use a tin based glaze or something, you can't do that over our glazes and get consistent color after firing.

You can paint bone china with our airbrushed underglazes, refire to 04, and glaze as usual. And Alchemy can take our earthenware horses, glaze them, and paint them with china paints. It's fun to share mud, and to try different things. As long as you understand the basics of your material, you will always get interesting results.  Joanie from Pour Horse