Ceramics & Glass
Antique ceramics have been around for thousands of years. Archeologists have been excavating utilitarian ceramic vessels dating back to 9000 B.C. The variety of material is enormous; from the simple pot to the most sophisticated porcelain forms. The major types of ceramics are earthenware, stoneware and porcelain, all consisting of a type of clay with an assortment of added minerals. They are all fired in a kiln at very high temperatures which increases the strength and rigidity of the vessel. A clay object can be glazed or unglazed and can be decorated before or after firing.
Earthenware has a long history going back centuries. All ancient Greek and Roman pottery is earthenware. It is made of selected clay’s, mixed with silica and other minerals and is usually fired at a low temperature. After it is fired it becomes opaque and porous and therefore cannot be used to store liquid unless it is glazed. After firing it turns a red-brown color and is known as terracotta.
Dutch Delftware is a type of tin-glazed earthenware that is glazed white and decorated with a cobalt oxide.
Stoneware is fired at a higher temperature than earthenware and is nonporous, opaque and slightly translucent. Adding a glaze makes stoneware hard and very durable.
There are two types of porcelain: hard paste and soft paste. Hard paste is “true” porcelain and is fired at extremely high temperatures. It is made from petuntse or china stone, ground to a powder and then mixed with kaolin, an aluminum silicate that is an essential ingredient for porcelain. After firing it remains white and becomes translucent. True china will resonate when tapped. It is similar to the porcelain of China.
In Medieval times wares from China were highly sought after. The Europeans tried to copy the formula for hard paste china but had difficulty because they hadn’t discovered kaolin and eventually invented soft paste china.
The soft paste porcelains are the products of 18th century French factories and the majority of 18th and 19 century English factories. Soft-paste or “artificial” china, a mixture of clay and ground glass, is fired at a lower temperature and is fired twice. The second firing is after the vessel is glazed. Soft paste, because it has a softer body, is more brittle and will chip more easily than hard paste china.
There are several types of glazes: salt glazes, tin glazes, celadon glazes and transparent glazes. Glaze is a glasslike substance fused to the ceramic body. On Chinese porcelain underglaze blue and white decoration used cobalt oxide and was applied onto the unfired vessel and then fired at a very high temperature. This created a permanent and smooth surface. Colors painted over the glaze are called enamels and are fired at lower temperatures and may need to be fired several times.
Gilding was also used to decorate porcelain and gives a very formal look. If you have gilded pieces they should be handled carefully and should not be put in the dishwasher as the gold will slowly wear off. Transfer printing is another decorative feature. It replaced hand painting and therefore was much cheaper to produce.
Susan Silver Antiques has a vast selection of interesting ceramics. She would love to talk to you about your collection.
Call me at (413) 229-8169