All About Ceramics

By Rebecca Ruger-Wightman

In a treatise written in 1850 by Joseph Marryat and extensively titled, Collections Towards a History of Pottery and Porcelain in the 15th, 16th, 17th, and 18th Century with a Description of the Manufacture, a Glossary, and a List of Monograms, Marryat introduces the subject with,

“The Plastic or Keramic Art is deserving of our attention, as being one of those first cultivated by every nation of the world. Its productions, though in modern times restricted to domestic use, were employed by the ancients for higher and nobler purposes. Pottery was the medium of expressing their homage for the dead, and the prize of the victor in the public games. Successful cultivators of the art were honoured with statues and medals, decreed to them by the State, and their names were transmitted to posterity by poets and historians.”

Ceramics, by a broad definition, refers to any object made from clay and subjected to fire. They’ve been around for a while, as far back as 24,000 BC, when humans discovered that clay dug from the earth could be mixed with water and heated to create animal and human figurines. Pottery making (ceramics as containers) began around 9,000 BC and then the Egyptians learned how to add glazes to their wares somewhere between 5,000-8,000 BC.

Sure, it’s unlikely we’ll find any of these scraps on our beaches, but there is plenty of sea glass pottery to be found. Though glassers refer to ceramics found on the beach as sea pottery or sea glass pottery, a more all-encompassing term would be sea ceramics, or sea glass ceramics, as ‘pottery’ is essentially a sub-category of ceramics, specifically meaning containers made from ceramic clay. 

Types of Clay for Pottery

Ceramics can be grouped into three basic categories-- earthenware, stoneware, and porcelain—which are determined by the clay used (body type) and whether fired at high or low temperatures. Regardless of the category, all ceramics will go through the same creative process: forming (shaping); firing (kiln baking); glazing (decorating, coating by various techniques); and re-firing (re-baking, to harden the glaze).

Earthenwares are porous ceramics made from rough clays fired at low temperatures (950°C and 1100°C), which can be leaky and will stain easily when left unglazed. Earthenware clays were the earliest used and are the most plastic (meaning they are easily worked). They contain iron and other impurities and will result in colors of red, orange, yellow, and light gray. Coarse earthenware, fired at 900°C -1200°C, is the softest and least compact, and may be generally known as simply earthenware, terra cotta, or pottery, and is more than likely unglazed. Coarse earthenwares were generally utilitarian wares mainly used for cooking and storage vessels. Refined earthenware would be fired at 1100°C -1200°C, is hard and compact and is only slightly porous. Referred to as ‘china’ or ‘semi-porcelain’, refined earthenware it is lighter than true earthenware and is usually glazed.

An example of ‘redware’, a punch pot c. 1765, currently housed at the Chazen Museum of Art in Madison Wisconsin.

Developed sometime after earthenware but before porcelains, stoneware clay is fired at higher temperatures (1160°C and 1225°C), making it non-porous. Stoneware clays are relatively more workable than true porcelain and are often grey when moist. Finished colors range from light grey and buff to medium grey and brown.

Porcelains are made from the finest clay, smoother and with finer particles, and fired at much higher temperatures (1300-1450° C), creating a vitrified or glass-like product. Kaolin clay, known for its purity, is used most widely for porcelains, and is most often found in lighter to whiter colors. While harder to shape, porcelain clays will result in a smoother body because of the finer clay, though it is very durable. There are three basic sub-categories of porcelain: hard-paste, soft-paste, and bone china.

A Wedgwood Creamware dessert dish, transefer printed on black enamel, likely 1780-1790, from a collection at the Victoria and Albert Museum. Photo courtesy the VAwebteam.

Hard paste porcelain is considered ‘true porcelain’, made from a  mixture of kaolin clay, ‘china stone’ (fledspar, a rock-forming mineral which make up more than 40% of the Earth’s crust), china clay, and flint.  The ingredients melt and fuse into a dense strong body, though it is possible for light to pass through it. Developed first in China during medieval times, it didn’t come to Europe (Germany, specifically) until the 18th century. The glaze on hard paste porcelain also fuses to the body (the glaze of soft-paste porcelain sits on top of the surface).

Soft paste porcelain, derided as ‘artifical porcelain’ was made in Europe before kaolin was discovered and used. It is a mixture of white clay and frit, a finely ground glass. Lime and chalk were added to fuse the white clay and frit. The body of soft-paste porcelain is considered granular or grainier because the ingredients do not melt together (fuse). Soft paste porcelain is more prone to chips and scratches.

Bone china is a type of porcelain and–as the name suggests—is created by the addition of bone ash (literally, the byproduct of incinerated animal bone). Bone ash gives the body of the plate a unique milky white color, adding a luminousness to the body of the dinnerware. Curiously, bone china is stronger, even though it’s softer than porcelain; because it’s less brittle, it actually is more resilient. Invented (or, perfected, as suggested by the aforementioned Joseph Marryat) by Josiah Spode II, it remained a mostly English product until the 20th century, made by Spode, Mintons, Wedgwood and Royal Doulton. Marryat contends that, “The bones are chiefly brought from Ireland and from America, and are principally those of bullocks, the bones of pigs and horses.”

While not strictly considered one of the main types of porcelain, there is also Bisque porcelain, which is porcelain left in the biscuit stage of production, meaning it is unglazed and somewhat porous. Bisque porcelain is manufactured chiefly as figurines, and was the most commonly used ceramic for German and French dolls made in the 1800s up until the early 20th century.

Types of Pottery

 


 Staffordshire Potteries (Location! Location! Location!)

Staffordshire Potteries

The Staffordshire Potteries is the industrial area encompassing the six towns—Tunstall, Burslem, Hanley, Stoke, Fenton and Longton—that now make up the city of Stoke-on-Trent in Staffordshire, England. In a perfect storm of potter’s delight, North Staffordshire was not only a great source of clay, salt, lead and coal— essential for ceramics’ making, but was also and perhaps more importantly home to Josiah Spode and Josiah Wedgwood, innovators of their time, among other notables in the potteries field.

It began when potter John Astbury of Shelton, discovered in 1720 that by adding heated and ground flint powder to the local reddish clay he could create a more durable and attractive white or cream ware. Yet, English ceramics of the 1700s were undistinguished, and little known in their own country, as they were eclisped by the fancier and better quality works of Meissen in Dresden and Svres in France. But this changed when Josiah Wedgwood improved upon the creamware design and make-up. He managed to produce a thin and light-colored earthenware that could be coated in a clear glaze. It was an instant success, made afffordable to the expanding middle class of Britain, its colonies and the Continent. Wedgwood presented it to Queen Charlotte, who was so pleased it that she ordered an entire tea service from him and was convinced to allow Wedgwood to rename  his creamware ‘Queen’s Ware’ and to refer to himself as ‘Potter to Her Majesty’.

Before he died in 1795, Wedgwood would have success with many new types of pottery, industrialize the production of pottery, and develop what is considered the origins of modern-day product marketing. Additionally, he spear-headed work on local roads and canals and sought to improve working conditions. (His financial successes would allow his grandson, Charles Darwin, enough leisure time to pursue his theories of evolution.)

Likewise, Wedgwood’s contemporary, Josiah Spode, made great contributions to the Staffordshire potteries, including a new method for underglaze blue transfer printing, and more notably, the perfecting of a recipe for quality bone china.

In 1785 there were a staggering 200 pottery manufacturers which employed some 20,000 workers. Records of the time and through the 19th century show that other noteworthy potteries in Staffordshire included Aynsley, Burleigh, Doulton, Dudson, Minton, Moorcroft, and Twyford.

This article appeared in the Glassing Magazine July/August 2018 issue.

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