History of Semi-Porcelain

The history of semi-porcelain is the history of ironstone.

Semi-porcelain is commonly referred to as "ironstone," but it also goes by other names. Though the fired clay body does appear somewhat vitreous (glass-like), it is actually a refined earthenware and not to be confused with true porcelain.

Differences from Porcelain

Porcelain clay is fired at temperatures above 1,300 degrees Celsius, and semi-porcelain, made from earthenware clay, is fired at around 1,200 degrees Celsius. A broken edge of semi-porcelain can be readily distinguished from porcelain.

Origins of Semi-Porcelain

In the early 19th century, English Staffordshire potteries began experimenting with a porcelain-like ware that could be cheaply mass-produced. Charles Mason patented this new ware in 1813, which he called "Ironstone China."

British Potteries

Staffordshire is the historic center of semi-porcelain (ironstone) production. By the mid-1800s, several Staffordshire potters produced ironstone because of the presence of high-quality clay within the district.

American Potteries

Americans quickly became consumers of semi-porcelain. After the Civil War, Ohio and New Jersey became the center of production in the U.S.

Identifying Semi-Porcelain

Semi-porcelain dishes are heavier and thicker than their porcelain counterparts (porcelain dishes are thin). Look for the terms, "semi porcelain," "ironstone china," "semi-vitreous porcelain," "English porcelain" or other similar names on the maker's mark.

References

• "National Museums Liverpool: Questions to a Ceramics Conservator"
• "British Pottery: Pottery Wares"
• "Trenton Historical Society: Marks of American Potters"

Resources

• "Stoke-on-Trent, England: North Staffordshire Pottery Industry"