Soft porcelain

Soft-paste porcelain (sometimes simply "soft paste") is a type of a ceramic material. The term refers to soft porcelains such as bone china, Seger porcelain, vitreous porcelain, new Sèvres porcelain, Parian porcelain and soft feldspathic porcelain, and is also used more narrowly to describe clay bodies mixed with glass frit that were used in the production of decorative figures and domestic wares in 18th century Europe. They were called "soft" because of their lower firing temperates compared with hard-paste porcelain.

There were early attempts by European potters to replicate Chinese porcelain when its composition was little understood and its constituents were not widely available in the West. The earliest formulations were mixtures of clay and ground-up glass (frit). Soapstone and lime are also known to have been included in some compositions. The first successful attempt was Medici porcelain, produced between 1575 and 1587. It was composed of white clay containing powdered feldspar, calcium phosphate and wollastonite (CaSiO3), with quartz. Other early European soft-paste porcelain, also a frit porcelain, was produced at the Rouen manufactory in 1673, which was known for this reason as "Porcelaine française". Again, these were developed in an effort to imitate high-valued Chinese hard-paste porcelain. As these early formulations slumped in the kiln at high temperatures, they were difficult and uneconomic to use. Later formulations used kaolin (china clay), quartz, feldspars, nepheline syenite and other feldspathic rocks. Soft-paste porcelain with these ingredients was technically superior to the traditional soft-paste and these formulations remain in production.

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