Making a large wall platter: Yucel Basegit demonstrates making a plaster model and mould of a large wall platter by the template technique.
Plaster moulding is one of the most widely used methods to shape ceramic products. In this process, different shaping techniques such as shaping via plaster lathe and template are frequently applied. All these routes comprise design of the product (sketch drawing), technical drawing with proper scaling and production of the model. In the technical drawing stage, the amount of shrinkage in the product during heat treatment and its final dimensions must be calculated and the model must be shaped accordingly. In this study, production stages for the plaster model of a 110 cm [empty set] wall plate by the template technique has been explained in details. This technique was selected in order to prevent possible deformations that could be observed during shaping of such large pieces and to obtain a solid product. The stages of plaster model production by the template technique are as follows;
* Design (sketch drawing),
* Technical drawing (by considering shrinkage and dimensions of the final product),
* Preparation of the templates by using technical drawing of the model,
* Shaping of the plaster according to the template and
* Removal of the shaped plaster model from the template.
* After completing the design and technical drawing stages of the wall plate, the template is prepared according to the technical drawing. The template could be made out of metal, wood or plaster.
The wooden template (Fig 1) stage is followed by shaping of the plaster model. In order to shape the plaster model, initially a pool is prepared in accordance with the shape and size of the model. To get rid of sticking of the plaster to the base, a soft soap is applied into the pool by using either foam or a soft brush. Then, the plaster is poured by sprinkling until it forms a thin layer on the water surface. Preparation stage ends up with mixing of the plaster from inner to the outer side and pouring it into the pool.
After the plaster reaches a viscous form, similar to yoghurt, the pool is opened and plaster model is shaped by turning around the previously prepared template. At the end of this process, the template is cleaned gently with soft foam and water.
The roughness on the surface of the plaster model shaped by the template is removed by a handsaw, scraper and emery paper and after that the model is soaped. By this way, the model was prepared for the moulding stage. The mould of the plaster model plate was planned to be composed of four pieces, one for the bottom and three parts for the sidewalls. After the shaping of the model, guides and templates used in production of mould sidewalls according to technical drawing are prepared for the shaping process of the mould.
The guides used in mould shaping and prepared for parts of the sidewalls are scaled in three equal pieces and they are placed on the plaster model after determination of the correct positions. These guides are fixed by plaster.
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A waterproof wooden piece (which is 2 cm in thickness and cut according to the shape of the model prepared to help shaping of the mould) is placed on to the plaster model. A heavy object should be put on to this wooden piece so that it does not move. Following the fixing of the guides, the plaster model should be surrounded by slabs starting from the first guide fixed for shaping of the mould to the sidewall to the second guide.
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Plaster is prepared to shape plaster model surrounded by slabs. This plaster is slowly poured into the pool around the model. Fibre pieces are added into the pool during plaster moulding so as to increase the modulus of the mould. (Fig 2) After the plaster reaches a viscous form, like yoghurt, the previously prepared template used to shape mould is removed to give a shape to the plaster. All of these processes are carried out for each part of the plaster model divided as equally scaled three parts. As-prepared views of the second and third parts are shown.
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Afterwards, the weight on the plaster model and the wooden guides are removed. The unlocking process is performed by using chisel, scraper and handsaw.
Then, to shape the last piece of the mould, it is surrounded by slabs and soft soap is spread on it. To prepare the last piece of the mould, more plaster is prepared. This new plaster is poured on to the plaster mould slowly until the bottom part of the model reaches to the same level with external walls. The fibres are added into the moulded plaster in order to increase its modulus. As the size of the model is quite large, previously prepared small-sized plaster slabs are added into this mixture additionally. Extra plaster is added on to this new form to complete moulding.
Following the moulding process, the plaster is left to freeze. When the mould solidifies completely, the slabs around the mould are opened and mould should be conducted. Mould and model are separated from each other and pieces of the mould are combined with each other.
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By combination of pieces, the inner part of the mould is ready for cleaning and retouching. The mould is left to drying after this fine-tuning process. When the mould dries completely, it is ready to use for the shaping process such as serial production by casting or pressing clay in to the mould.
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Asst. Prof. Yucel Basegit is currently head of Ceramic Department at Faculty of Fine Arts, Canakkale Onsekiz Mart University, in Canakkale, Turkey. (The experimental part of this study was carried out by Yucel Basegit and Kamuran Ak)
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|Date:||Nov 1, 2012|
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