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.