The production of porcelain for electrical insulation — I

This series of articles is presented with a riew of acquainting the electrical engineer with the composition of porcelain, the raw materials, and processes employed in its manufacture, and with the structure and the physical properties of the finished product. The principles underlying the art will be discussed as well as the reasons for using certain materials or certain processes. Recent developments in porcelain for automotive purposes have clearly demonstrated that the transmission porcelain of the future will be an improvement over that of the porcelain of today, provided however, that the consumer of transmission porcelain will be willing to pay the increased cost, or provided the manufacturer will be able to lower his cost on the improved product when sufficiently developed. The fact that the porcelain used in transmission work today would make only inferior spark plugs makes it safe to predict this future improvement in transmission porcelain. The present article deals briefly with the history of porcelain and its definition. Generally porcelain is made of a mixture of ground feldspar, a mineral which melts to glass and makes the porcelain vitreous when fired; clay which makes it possible to form the unfired porcelain and have it retain its shape; and fine silica sand or quartz which acts as a filler or non-plastic material. These three materials are mentioned several times before they are described in detail but this brief description is sufficient for the present. The beginning of a description of ceramic raw materials is given. The writer wishes to express his thanks to Mr. A. V. Bleininger for his cooperation and suggestions in preparing these articles. Also to Prof. Albert Peck for his assistance in preparing and discussing the photomicrographs.