Introduction to pottery and porcelain

You may be familiar with it as 'china', but the ceramics category of antiques covers a surprisingly wide area of collecting, from functional pottery wares to highly prized pieces of porcelain.

Ceramics can be broadly divided into two main groups: pottery, which is opaque when held to the light; and porcelain, which is translucent. Within these two categories is a huge range of different wares which evolved over the centuries as new manufacturing techniques were developed.

If you're just beginning your collection, the multitude of pottery wares produced during the 19th century could be an ideal starting point. During this period the Staffordshire area produced vast numbers of inexpensive household and decorative objects, which at the time cost a few shillings or less. These are still abundantly available and, although collectable, have remained relatively inexpensive.

"Porcelain has long been highly prized"
Porcelain has long been highly prized and tends to be more expensive than pottery. The field is divided into two main groups: hard-paste porcelain and soft-paste porcelain. Many pieces have marks of some type but these are no guarantee of authenticity because many factories copied each other's marks to make their products more desirable. Value is usually a matter of size, age, rarity, decorative appeal and, above all, condition. European 18th-century porcelain tends to be very highly priced but you can often buy damaged pieces for a fraction of the cost of those in perfect condition.

When you first look at a piece of pottery or porcelain, an understanding of the materials and techniques used in its manufacture can help you identify its origin, date and how much it might be worth. The three main factors to assess are material, glaze and decoration.

Materials

Pottery
This has a relatively coarse texture compared with porcelain, and is usually opaque if held to the light. The two main types are earthenware and non-porous stoneware.

Glazes

Glazes can be translucent, opaque or coloured. Hard-paste porcelain was given a feldspar glaze, which fused with the body when fired. On soft-paste porcelain the glaze tends to pool in the crevices. A variety of different glazes was used on pottery and porcelain. The main ones are:

Lead glaze Used on most soft-paste porcelain, and on earthenwares such as creamware. Tin glaze A glaze to which tin oxide has been added to give an opaque white finish. Salt glaze A glaze formed by throwing common salt into the kiln at about 1,000°C (1,800°F) during the firing.

Decorative techniques
Decoration can be added before or after glazing. Underglaze decoration means the colours have been added before glazing.

Underglaze blue
Blue pigment, known as cobalt blue, was used on Chinese blue and white porcelain, European delfware and soft-paste porcelain.

Overglaze enamels
Overglaze enamels were made by adding metallic oxide to molten glass and reducing the cooled mixture, which when combined with an oily medium, could be painted over the glaze and fused to it by firing. The range of colours was larger than the underglaze colours.