Ceramics and Ceramic forming techniques
(By Aynur Karaagac)
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The term 'ceramic', which is derived from the Greek word 'keramikos' meaning pottery, is used to mention every ceramic product such as baked soil, polished tiles and porcelain (soft, hard or twice fired ceramic). The art of making pottery by baking in furnace is called today as "ceramics".
Ceramics is the art and science of making things from inorganic, non-metallic materials by the action of heat. The term includes the purification of raw materials, the study and production of the chemical compounds concerned, their formation into components and the study of their structure, composition and properties. Ceramic materials may have a crystalline or partly crystalline structure, or may be of glass. They are either formed from a molten mass that solidifies on cooling, or formed and matured by the action of heat.
Ceramic forming techniques
Having a strong background by being the first technique that the human being has learned, ceramic is still applied today with similar techniques used ages ago. Ceramic products differ from each other both in terms of the mixture of the mud and the baking method.
All kinds of mud consist of clay in different qualities (the element that gives form) and the oil removing elements (soil, quartz, ash, pieces of plants, straw, grinded calcite etc.). By adding a melting substance makes the mud glassy and thus it transforms into the porcelain. Generally, the 'ceramic mud' material has various types. These kinds of mud are all different from each other in terms of their chemical qualities, patterns and colors; however, their common characteristic is the feature of being shaped easily and artificially. The thing that qualifies the mud as good is the ability of keeping glaze and becoming usable, durable, and glassy.
Initially, the ceramic product is designed on paper. Then, the design is brought into 3D by choosing the appropriate mud (casting, red clay etc.). In that process, the designer is supposed to choose the most convenient forming method by being aware of that different formations come out by applying different degrees of heat. The final product needs to be the one which forms a whole with its production method, its shape, decoration and glaze. That's why, trying to solve all the details on paper without having the knowledge about the characteristics of the material, may result only in waste of time and material.
In product design, aesthetical values should not be ignored. These values may differ from each other depending on the purposes of use. For instance, tableware products should have the forms that the user can personalize and organize in a way he/she wants. Each pieces of sets like dishes and salt containers should be considered as a part of all the other pieces of the sets like handles and shaped in order to function truly and form an union in terms of material and form.
As already told, while bringing the ceramic into 3D, the most convenient forming method should be chosen. There are many factors that play important roles on choosing the forming method. For example, the structure of the mud, its aim and the field of use, the efficiency of the production, the formal structure of the product needs to be known. By combining the techniques of hand-shaping such as making stripes, preparing mold and making plate, it is possible to form products. While giving shape by hand, mud is kneaded well to make it mix with the mixture and to make the air flow out. The presence of the air may result in some cracks while the product is left for drying or is placed in the furnace. If the kneaded mud will be given shape by 'plating technique', by the help of a roller-pin or wooden molds, a number of plates in different thickness and similar dimensions with the product can be formed. Because the thickness of the plate forms wall thickness of the product, it shouldn't be too thick. The tools that are used to give the shape of mud are called 'ebejuar'. Sticking two different surfaces needs some notches on both sides of the surfaces that should also get wet in order to be taped.
The sticking details are very important while they are applied on mud. Surfaces that are not stuck well may crack during the drying process. Beside the plating technique, there is another technique called 'striping technique' in which the hand made stripes are stuck together on a floor of mud. Another method of giving shape by hand is 'lathe'. Lathe is used when symmetric and round shapes are designed. In lathe technique, it needs to be paid attention to prevent the mud from getting away from the center in order to transform the mud into its form in a balanced way. Lathe is a technique which develops only with practicing. Ceramic mud can also be used in forming wall-panels, sculptures and mass models of some products by taking or adding some pieces. However, after building a mass model, the model needs to be emptied to a determined wall thickness.
When ceramic forming techniques are considered in terms of industry, it is observed that there are some techniques like pressing or casting into a plaster mold (the reason for the usage of plaster is the plaster's ability to assume the water in the mud and to make the mud stick on the surface and dry to form wall-thickness) that are based on mass production. If the product will be given a shape by casting into a plaster mold, technical drawings of the product should be drawn by considering the mud's shrinking ratio and the model should be prepared with plaster lathe. The pins, which make the plaster pieces connect to each other, are placed between the pieces. While making a plaster mold, the details for preparing plaster are also very important. Molds are shaped according to the type of casting (empty or full casting). Large forms like service plates and trays are formed by full casting while empty forms like cups are formed by empty casting. Another method in plaster molds is to press dry mud into the mold by automatic template lathe.
Before being placed into the furnace, the shaped product needs to be fully dried. Drying should be progressed slowly according to the products details, otherwise the product may crack during the drying process or when it is left in the furnace to be baked. The dried surface product is finally applied by sandpaper or foam rubber in order to form a smooth surface and placed in the furnace. The first part of baking must be at least 950 degree Celsius furnaces. To make the baked product durable, glaze is applied with an appropriate technique (plunging, spraying, pouring, dusting etc.). The glazed product is baked for the second time at a high temperature. Temperature of the furnace differs according to the type of the glaze. Glazing the product adds a nice visual effect and a hygienic quality to the product. Having opaque and shiny types, glazes can be varied by adding color.
A ceramic product is applied the same procedures (primary product-drying-baking-glazing-baking) even if the types of their mud and production methods differ from each other. If decoration will be applied on the product, under-glaze and over-glaze paints are used. In the end, a successful process creates a functional and high-quality product. That's also an important factor for both, the manufacturer and the user.
* Works in the photographs are belong to the students of ITU Department of Fine Arts.