• The Potteries Museum
• Gladstone Pottery Museum
• Ford Green Hall
• Etruria Industrial Museum

• Home
• Browse Collections
• Photographic Archive
• enquiry service
• Object of the Month

• Browse Collections
  • Ceramics Collections
    • 18th and 19th Century
    • 20th Century
    • Islamic Ceramics
    • East Asian Ceramics
    • Slipware Collection
    • Studio Pottery Collection
    • Minton
    • Collections
    • Research Resources
      • Factories
      • General
      • People
      • Processes
        • Bone and Bone China
        • Bricks
        • Clay In North Staffordshire
        • Decorative Techniques
        • Gilding
        • Glazes
        • A brief History of Tile Making
        • Jiggering
        • Parian
        • Saggar Making
        • Throwing
        • Underglaze Blue Printing
    • Ceramic Links
    • Ceramic Enquiries
    • Information Sheets
  • Local History
  • Natural History
  • Decorative Arts
  • Fine Arts
  • Our Online Collections

Bone and bone china

Josiah Spode II (1754-1827) introduced his new bone china pottery in c.1797. This was to become the English solution to the quest for porcelain. Technically bone china is a form of hard paste porcelain because it is a mixture of clay and another non-glassy material.

The standard formula is 25% china clay, 25% Cornish stone, 50% bone ash. Bone china became the English porcelain because it is less liable to loss in firing than soft paste porcelains which contain glass. The firing temperature is much lower (1250 C) than for hard paste porcelain (1400 C). The potters could use their existing methods and ovens. The brilliance of enamel colours and gold was greater than on other porcelains.

It very quickly became a popular body for several reasons: 

• Reduced trade with China, caused by very heavy import duties on porcelain (108% in 1799);
• Less merchant shipping due to the need to sustain naval and military forces overseas;
• The patronage of the Prince of Wales, leader of taste at the beginning of the nineteenth century;
• The growth of the professional and merchant classes, which provided a market.

It was easy for existing factories to convert to making bone china because the sequence of processes as well as the glost and enamel firing temperatures were the same as earthenware. Bone china is more difficult to use in a plastic state than earthenwares, but quicker to cast with than earthenwares.

Calcined bone ash 

Calcined bone ash is used in producing bone china and makes up about 50% by weight of the final body recipe. It is produced from animal bone, which is first processed to remove any adhering meat which is generally sold as pet food.

The bone is then treated to remove glue, which is processed and upgraded for use in normal applications where glue is used, and also for the sizing of expensive paper. The raw bone which is left after the meat and glue have been extracted is then heated to about 1000 C at which temperature any residual organic material is burned off and the structure of the bone is changed to a form suitable for the manufacture of bone china. The high temperature used also sterilises the bone.

Before use the bone is finely ground with water before being included in the bone china body and it is calcined bone which gives traditional English bone china its translucency and whiteness.