Pottery & Ceramic Guide

The technologies involved in manufacturing ceramics are based on the affinities between earth, water and fire; water gives the earth its plasticity and the fire then makes it hard.

Clay comes from the decomposition and hydration of rocks. The commonest clays belong to the feldspar family, of which silicon is a member. The main components of clay are silicon and aluminum, combined with molecules of water; clay is hydrated aluminum silicate. It is rare to find a clay which is suitable for use immediately; usually it is necessary to mix together various mineral materials to create a ceramic paste suitable for the intended purpose.

Once the piece has been made, the piece is allowed to dry; it undergoes a process of shrinkage, which is variable depending on the type of clay.

Being used, thus facilitating mold removal (if in a mold). When the clay has the consistency of leather, finishing operations can take place; trimming, which gives the piece its final thickness and profile by removing small particles of clay; removal of the mold; garnishing; addition of handles and spouts which are “welded” using slip; and decoration. Decoration of the raw material can be done either by removing material (for example perforation, engraving motifs as in the Grafitti pieces).

After drying, the piece can be fired. Two firings usually take place. First – known as the bisque firing- is a slow firing process because there is still a lot of water present which could cause the piece to break; ( this causes the virtually complete dehydration of the clay; the water in the particles is eliminated, which means that the paste permanently loses its plasticity and acquires a new consistency) . After this 1st firing colored decoration takes place in the form of the application of a composition of silicon-(which will have the structure of glass after firing) - and metallic oxides which are called enamels or glazes, or it is covered with varnish if it is transparent and its fired the 2^nd time.

The base product , silicon, melts at 1700* C it is therefore necessary to add fluxes (such as LEAD) to reduce the melting point. Metal oxides give the enamel its color; depending on whether the firing atmosphere is oxidizing or reducing, the metallic oxides will take on different colors.

Enamelling of the piece can be compared to painting , with the difference that the colors are not revealed until after they have been tried in the fire. The application of enamel can be done by immersion, pouring, sprinkling or, in the same way as painting, by marking motifs using an artist’s brush.

POTTERY FACTS

Maiolica (pronounced ma-ya-li-ca), a tin-glazed earthenware, can trace its roots back to 9th century Islam. It was first introduced into Italy during the 13th century from Moorish Spain, shipped by traders from the island of Majorca, thus giving the Spanish lustreware the name Maiolica (although it could also derive from the Spanish obra de malaga, ie, lustreware). Italian potters glazed their red ware pottery with a white tin glaze and then used metal oxides to decorate the unfired surface. A thin final coat of clear lead glaze (called Coperta) was applied to smooth and make the decorations more glossy. The correct technical term for the process is 'in-glaze' painting.) The term maiolica at first referred only to lustreware, it later came to be used as a generic term for all tin-glazed earthenware.

Italy was the pivotal point from which maiolica, with its new-found status in the decorative arts, was to spread throughout Europe and even further afield. Some of the most influential to take birth in Italy is Faenza, Deruta, Istoriato maiolica and High Renaissance. From Italy, the fashion for decorated tin glaze spread throughout Europe. In the early 1500's, Italian potters started to emigrate and set up workshops in Spain, France, Antwerp and later in Switzerland. From Antwerp, the technique traveled to Holland, Germany and England. From Switzerland, it was to move eastwards to Austria, Bohemia, Moravia, Slovakia and Hungary. In each of these countries, the style of work was at the outset predominantly Italian, but gradually regional characteristic began to creep in and new, distinct styles emerged. Literally, a plethora of tin-glazed earthenware, from the original maiolica, to French 'faience', Dutch and English 'delftware', and Minton 'majolica', appear throughout history.

Potters, professional instructors, university art professors, and potter reference material often refer to contemporary (20th century) low-fire earthenware as 'Majolica'. It is the nature of the tin-glazed earthenware, the in-glaze techniques, the dedication to the beautiful and complex methods, that has allowed this tradition to survive. Without this dedication by artists and artisans, a tradition that dates back 1100 years would fade into obscurity... a mere footnote in history.

Stoneware
This is a durable, weighty ceramic which contains stone that can withstand daily use and is chip-resistant.

Earthenware
This is pottery made from actual clay which is porous. It requires a glaze to finish it and add luster. Its properties allow it to be fired for bright colors.

Porcelain
It is one of the most durable ceramics, made of refined clays. It can be a white or gray color. However, it is fired at high temperatures which ensures a hard, glossy surface that is resistant to scratching. It is extremely strong.

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