What natural materials are needed to make porcelain?

KAOLIN is a key ingredient, which is made from kaolinite plus other materials such as feldspar, ball clay, glass, bone ash, quartz, and alabaster.

English Bone China is typically made from two parts of bone-ash (source of Calcium), one part of kaolin (an alumino-silicate), and one part feldspar (silicate) rock, found in granite. TYPESof Porcelain clays: Hard-paste, Soft-paste, and Bone China. Within these three types there is an almost infinite number of individual recipes/formulas which have different casting, molding, firing and final color and appearance characteristics. For example, 'Ming Porcelain' is made to a very old formula, and produces a top quality translucent Porcelain (clay) suitable for throwing, moDELLing and very fine detail. One manufacturer of (Chinese) porcelain clay lists his raw materials:

* Montmorillonite * Kaolinite * Quartz (free silica) The chemical analysis of his resulting Porcelain clay is:

Silicon Dioxide (SiO2) 62-70%

Aluminium Oxide (Al2O3) 17-23%

Iron Oxide (Fe2O3) 2.5-5.3%

Calcium Oxide (CaO) + Sodium Oxide (Na2O) 2-3%

1. Typical analysis(a) of another manufacturer's 'White Porcelain' ... Silicon Dioxide 60.9%

Aluminium Oxide 27.4%

Potassium Oxide (K2O) 2.3%

Trace amounts of other key chemicals 1.8%

2. The basic mix for Bone China clay has about 50% calcined Bone Ash, so the volume of the calcium compounds is significant (>23%), but the Silicon and Aluminium content is correspondingly lower. Silicon Dioxide 29%

Aluminium Oxide 16.8%

Calcium Oxide etc 23.0+%

Potassium Oxide 1.34%

Other key chemicals 1.87%

SUMMARY: Although the basic ingredients are the same, there are many different types of porcelains, and many different recipes/mixes. There are even some secret formulas! You can also have a porcelian clay made to your own recipe! ---- Note:

(a) The percentages do not total 100%, but give an indication of the chemical composition.

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