History

Ceramic Restoration, Repairs and Conservation to all Ceramics, Stoneware, Glass, Porcelain and pottery

Text Box: Ceramic 'Ceramic' is a broad term covering all types of fired clay, including terracotta, earthenware, stoneware and porcelain. Ceramic objects range from utilitarian and decorative vessels to tiles, sculpture and dolls. Ceramic objects are made from different types of clay, with or without additives; which may be painted, glazed, enamelled or gilded. Clays are natural products formed by the long-term weathering of rocks in the earth's crust. As techniques improved, potters use ever more complex mixtures of clays and minerals to produce the required properties and effects. The firing of the shaped clay usually consists of several firings at different temperatures. The first or 'biscuit' firing stabilizes and sets the object, after which the piece may be glazed and decorated. Firing techniques and methods greatly influence the final properties of the object. Low-fired pottery and soft-paste porcelain are more fragile and porous and more prone to chipping, etc, whereas high-fired stoneware and hard-paste porcelain are more durable. There are several broad categories of ceramic material. The most basic but still widely used form is low-fired pottery or earthenware. Examples of this relatively soft and porous type include Neolithic, Greek, Roman and Chinese artefacts, and a large range of studio pottery. Also included is tin-glazed Hispano-Moresque pottery and Italian majolica, French faience, Dutch delft and English delftwares and Staffordshire. The second group are higher fired wares and include vitrified, non-porous and durable stoneware, Chinese Yueh ware and celadons, salt glazed Rhenish and English stonewares, lead glazed Staffordshire stoneware and cream wares, and Wedgwood's unglazed basalt and jasper wares. Porcelain is a hard white material with a degree of translucency. Hard paste 'true' porcelains include Chinese and Japanese porcelains, unglazed biscuit wares, as well as the products of Meissen, Vienna, Sèvres, Plymouth and Bristol. Soft paste or 'imitation' porcelain was produced by Capodimonte, Rouen, St Cloud, Vincennes, Sèvres, Bow, Chelsea, Derby, Worcester and many others, and also includes bone china and unglazed Parian wares. Glass 'Glass' may appear to describe a single unvarying substance, but like 'ceramic' it is a broad term that refers to a number of different but related materials. The main raw materials of inorganic glass are silica (sand), an alkali (usually sodium oxide or potassium oxide, producing respectively soda and potash glasses), and calcium (lime). Modifiers, stabilisers and colourants are added to make the glass workable or to add decorative characteristics. Glass is an intriguing substance. It is generally regarded as a supercooled liquid, having characteristics of both solid and liquid phases. If left long enough (perhaps over centuries), a vertical sheet of glass 'runs' to become thinner at the top and thicker at the bottom. This is not the only characteristic that changes over time. Although strong when first made, glass acquires minute surface defects that act as points of stress concentration. These in turn initiate deeper flaws, and the process carries on in an accumulative fashion. Hence old glass is more fragile than new glass. Glass may be clear or modified and coloured by the addition of metallic oxides, metal particles, and opalising agents. Lead glass or lead crystal is a 'soft', sparkling glass that is easily cut and incised. Often known simply as 'crystal', lead crystal is produced by adding lead oxide to glass and should not be confused with rock crystal, a naturally occurring form of quartz. Glass can blown, floated or moulded, and may be decorated in both molten and hardened states. The range of glass or glazed objects found in museums around the world today is vast with familiar utilitarian and decorative glassware and glazed ceramics, sculptures, enamelled objects, chandeliers, mirrors, stained glass windows and fragments, reverse paintings on glass, and so on. Ceramic and glass are of great historical value and worth restoring and conserving. Restoration and Conservation is as much an in investment in the past as it is in the future.

History