Ceramics is fired clay, often covered with a glaze.
More about this on this page.
Ceramics: how to make
Forms made of clay have to be thoroughly dried (4-14 days),
be fired (2 days), covered with a glaze and
fired again to have the glaze melt (2,3 days).
Different clays harden at different temperatures.
Different glazes melt on different temperatures.
That is why the waiting period for an order can quickly grow.
Because the clay has to dry, and because a kiln has to be filled
with glazes of the same temperature
(firing a kiln for just one pot is very expensive).
Earthenware, Stoneware and Porcelain
Ceramics is the collective term for baked clay.
Unbaked clay is not ceramics; like mud,it will remain soluble in water, even when it has been dried and became hard.
When baking clay, from approximately 600 degrees it will irreversible become ceramics, and be no longer soluble.
Ceramics is subdivided in earthenware, stoneware and porcelain.
Earthenware is ceramics that is fired between about 980 up to 1100 degrees.
It is a porous kind of ceramics; if these are plunged in water, it will absord it (but will not dissolve). Colours in glazing or other decorative materials, will not easily burn on this temperature, therefore earthenware is easily coloured (brightly).
Earthenware is useful for plant pots because it can keep moisture in. Also it's practical for cheese fondue-pans or tajines. Terra cotta is also earthenware but unglazed.
Stoneware is a kind of ceramics which is fired at approximately 1100 up to 1350. The clay melts to a stone-like hardness. The volume of the clay shrinks as a result, much more so than earthenware; by the consequently increased density of the clay, it becomes impermeable.
For this reason, stoneware is very useful for crockery. Or gin pitchers. Or oven dishes.
Porcelain is in fact also stoneware, but made of other clay. That is to say: porcelain clay.
This (composed) clay is particularly white and can withstand temperatures up to 1400º (or more).
At that temperature she will become even harder than other stoneware.
Unique to this clay, beside the colour, is that she will become translucent, when fired at higher temperature and at maximum 4mm cross-sections. The light will pass throught it, like it does with paper.
This whole story illustrated in short > take a vase, made of porcelain clay:
• baked on 1000º it will become porous ceramics, it can easily be coloured.
• baked on 1200º it will become impermeable; some colours will burn at this temperature; they simply disappear.
• baked on 1400º it will shrink more than 10%, which is much, and the vase will become translucent.
Porcelain and Delftware in the Netherlands
Porcelain was introduced in the Netherlands at the start of the 17th century. The VOC (Dutch East Indian Company) imported this expensive stuff from China and later Japan.
The import did concern ceramics, the fired product, not the clay. The recipe of this clay was kept well a secret.
Cheap imitation took place in the Netherlands in mainly Delft, by applying white glaze on not-white clay. When painted on it, with blue (cobalt) oxide that will melt into the glaze during firing, a piece of Delftware is obtained. That looks like the Chinese porcelain. But is not the same.
Only at the beginning 18th century, after a long research, in Dresden the recipe for porcelain was discovered by an alchimist and geologist. At first a red version of it (also beautiful), later the white.
The recipe spread itself rapidly over Europe. Variations with bone-ashes were developed, that results in a less white porcelain and can be fired at a lower temperature.
It made the French Sèvres big, as well as the English creamware (especially known from Wedgewood's adaptations).