Conservation and restoration of ceramic objects

Conservation and restoration of ceramic objects is a process dedicated to the preservation and protection of objects of historical and personal value made from ceramic. Typically this activity of conservation-restoration is undertaken by a conservator-restorer, especially when dealing with object of cultural heritage. Ceramics are created from a production of coatings of inorganic, nonmetallic materials using heating and cooling to create a glaze. Typically the coatings are permanent and sustainable for utilitarian and decorative purposes. The cleaning, handling, storage, and in general treatment of ceramics is consistent with that of glass because they are made of similar oxygen-rich components such as silicates. In conservation ceramics are broken down into three groups: unfired clay, earthenware or terracotta, and stoneware and porcelain.

It is in the nature of all the materials used for construction to eventually degrade and deteriorate. Degradation of an object occurs as a result of the interaction between the environment or with the materials that form the object however, in the case of ceramics, environmental factors are the major cause. There are several ways in which ceramics break down physically and chemically.

Additionally the type of ceramic will affect how it will break down. Unfired clay, like mud and clay adobe, is clay that is fired under 1000 °C or 1832 °F. This type of clay is water-soluble and unstable. Earthenware is clay that has been fired between 1000-1200 °C or 1832°-2192 °F. The firing makes the clay water insoluble but does not allow the formation of an extensive glassy or vitreous within the body. Although water-insoluble, the porous body of earthenware allows water to penetrate. A glaze can be applied that will protect the vessel from water. Due to its porosity, earthenware is susceptible to moisture and creates problems including cracks, breaks and mold growth. Porcelain and stoneware is fired at the highest temperatures between 1200-1400 °C or 2192-2552 °F. Porcelain clay mixtures are fired to create a non-porous and very hard surface. However, the materials also create a very brittle surface which increases the potential for chips, cracks and breaks.

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