I am back from my trip to Virginia, where I visited the DC area and Williamsburg. In colonial Williamsburg, there is a great museum dedicated to decorative arts. Of course, pottery and ceramics is a large part of the museum. They had a great collection of earthenware pots and jugs. Also, great educational displays on the differences between earthenware, stoneware, and porcelain.
Earthenware is porous, fired at low temps, needs a glaze to be impervious to liquids and is opaque. Earthenware can be yellow, red, brown or black.
Stoneware is fired in the mid-range temperatures, does not need a glaze to be impervious to liquids, is good at withstanding thermal shock, and can be slightly translucent if thinly potted. Stoneware can range from white to gray, tan, borwn, and red.
Porcelain is fired at high temperatures, it does not need a glaze to be impervious to liquids, is great at withstanding thermal schock (they use porcelain for those space shuttle tiles), and is translucent if thinly potted. Porcelain is always white.
Porcelain or china is made of kaolin or china clay, which is a refractory white clay or pure alumina silicate. It is usually glazed with powdered petuntse or feldspathic rock (volcanic rock). The great stumbling block to creating china in Europe was not the ingredients but creating a kiln that could fire hot enough. They figured it out in Meissen, Germany around 1710. The first porcelain, or China, was developed in China around 610-907 AD.
Personally, a display explaining transfer ware, porcelain decorated with designs created originally on copper engraving plates, was a highlight. This has always been a minor mystery to me. How did they do that? Copper plates are flat and cups and bowls are not. Remember they came up with this process in the mid-1700s. No plastic or rubber was available to them. So how did they transfer those designs?
The answer was linen. They printed the design onto linen fabric and then wrapped the linen around the object. They left the linen on the porcelain and then it fired off in the kiln leaving the design. Cool, huh?
The summer classes at Irving are going great. We were joined last week by Skylar and her grandmother, Carol, for this session. Skylar will be an eigth grader next year; she has been working on a scene featuring a wagon train. Last night, four students started on a Santa Claus plate. Also, one of my students is doing a portrait of her mom in a black monochrome.