Porcelain in Name Only
Notwithstanding Indigenous peoples of the Americas, during the early years of the last century American individuals using their hands to form clay into pottery were referred to as vessel makers. Ceramic vessel making was practiced as either vocational education (to provide skilled labor to industry), therapeutic activity for people with nervous disorders or as a hobby.
Serious hobbyist frequently dug their own clay
from local deposits, built their own wood fired kilns and wheels and mixed
their own glazes. It was a process of trial and error to teach yourself
to be a potter before 1950.
By the time I was introduced to clay in the late
1960's and taking my first baby steps as a ceramic artist, formal training
existed. Suppliers mined raw material and sold clay and raw materials to
schools and hobbyists. Clay was mined or manufactured as low-fire (earthenware),
high-fire (stoneware) and porcelain. Low-fired
earthenware cannot be made vitreous and historically has been limited to
building bricks and tiles. The red pots available
at the local garden center are an example of earthenware. High-fired stoneware
was preferred by the potter because of the effects of reduction firing and the
plasticity of the brown or grey stoneware.
Porcelain clay was more commonly used to produce commercial ware in
plaster molds. Porcelain can be identified from its hardness, brilliant white
color, and is translucent when thin.
Chinaware was a term loosely used to designate
white clay bodies that were fired between cone 4 to cone 8. Although hard
and durable, it should not be confused "with even harder and more
translucent porcelain bodies fired to cone 10 to 16" (page 143. Ceramics:
A Potter's Handbook, Glenn Nelson, 1971). Over the years the term chinaware
disappeared from being used to describe clay and was replaced by “white
stoneware.”
The reason for
this history is that I was having a conversation with a younger ceramic artist related
to the porcelain clay used at a community makers space the other day. There appeared to be a misconception that the
porcelain clay used at this makerspace needs to be treated differently than the
Cone 5 Laguna B-Mix white stoneware that is also being used.
Today there are
two types of porcelain, true, hard-past porcelain, and artificial porcelain*
(*Britannica.com). Bone China porcelain
is the original hard-past porcelain used by Chinese potters a century ago. It
is extremely smooth. When fired at
extremely high temperature (Cone 10 - 16) the clay fuses into something that is
closer to hard glass, white-white and slightly translucent.
Bone China clay
is manufactured today. It is still prized for its white-white, translucent,
fragility. But alongside these clay
bodies one will find white stoneware clay bodies that fire from Cone 2 to 10.
These white stoneware clay bodies, referred to as Porcelaineous Stoneware
(Digitalfire.com), provide more plasticity and forgiveness than Bone China
porcelain, while providing the smoothness and whiteness (but not the white-white
fragility of porcelain.) Manufactures continue
to develop better and better Porcelaineous stoneware, blurring the line between
white stoneware and porcelain even more. True, “real,” hard-paste porcelain can still
be recognized by its hardness and Cone 10-16 firing range.
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