Bone china

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BLW Bone China Chocolate Cup

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Bone china is a type of porcelain that is composed of bone ash, feldspathic material, and kaolin. It has been defined as "ware with a translucent body" containing a minimum of 30% of phosphate derived from animal bone and calculated calcium phosphate. Bone china is known for its high levels of whiteness and translucency, and very high mechanical strength and chip resistance. Its high strength allows it to be produced in thinner cross-sections than other types of porcelain.

History

The development of bone china is attributed to Josiah Spode in the early 1790s in Stoke-on-Trent, England. Spode's formula for bone china was adopted by other English manufacturers and remains the standard English body. The production of bone china is labor-intensive and requires a high level of skill, which has traditionally limited its production to a few countries.

Composition

Bone china is composed of:

• 50% bone ash
• 25% kaolin
• 25% feldspar

The bone ash used in bone china is made from cattle bones that have a lower iron content. The bones are crushed, degelatinized, and then calcined at high temperatures to produce bone ash.

Manufacturing Process

The manufacturing process of bone china involves several stages: 1. Preparation of the body: The raw materials are mixed together and ground to a fine powder. 2. Shaping: The body is shaped into the desired form using various techniques such as slip casting, jiggering, or pressing. 3. Firing: The shaped body is fired at a high temperature to create a bisque. 4. Glazing: The bisque is glazed and then fired again at a lower temperature to create the final product.

Characteristics

Bone china is known for its:

• Translucency: Due to its high bone ash content, bone china is more translucent than other types of porcelain.
• Whiteness: The bone ash gives bone china a unique white color.
• Strength: Bone china is stronger and more durable than other types of porcelain.
• Chip resistance: The high strength of bone china makes it more resistant to chipping.

Uses

Bone china is primarily used for:

• Tableware: Including plates, bowls, cups, and saucers.
• Decorative items: Such as vases and figurines.

Related Pages

• Porcelain
• Josiah Spode
• Stoke-on-Trent
• Kaolin
• Feldspar