Historical sketch of the electrical porcelain industry

[Trade Journal]

Publication: Journal of the American Ceramic Society

Columbus, OH, United States
vol. 6, no. 1, p. 312-314, col. 1





Porcelain Mixtures


Although the manufacture of porcelain is a very old art, the credit of the origin and development being given to China, where the industry flourished during the middle ages, the use of porcelain as an electrical insulation is comparatively recent. The Germans were the first to use porcelain for this purpose and as nearly as can be ascertained the date of this initial application was about 1852. At that time in attempting to lay telephone wires underground it was found that they could not be properly insulated with gutta-percha, the chief insulating material then in use. Mixing clay with the gutta-percha and finally vulcanizing the gutta-percha with sulphur did not produce satisfactory results. This led to overhead construction but the same troubles of unsatisfactory insulation were encountered. The gutta-percha clay mixture was more satisfactory than the vulcanized material due to the fact that the latter attacked and corroded the copper wires and this fact led to the use of baked clay and finally the more or less vitrified porcelain.

In America so far as the writer can learn the first electrical porcelain was made by the dust or dry process and the credit for this accomplishment goes to the Greenwood Pottery Company of Trenton, N. J. This was in 1879. The articles were two-piece insulators, probably knobs, and were given two firings, one biscuit and one glost. Mr. Joseph Crossley of Trenton made the dies used in making these pieces and at the same time laid the foundation of what is now the Crossley Machine Company.

Mr. David Crossley, now president of the Crossley Machine Company, feeling that the electrical porcelain industry presented a very large field and unlimited opportunities, started experimenting with different articles, bodies and glazes in 1890-91. His samples were fired by the different potters in Trenton. Experiments being constantly retarded by waiting for the return of his samples, a delay of two weeks being customary, Mr. Crossley became discouraged with his arrangement and decided to try glazing an unfired piece just to see what might happen to it during firing. Lo and behold! The piece on coming from the kiln could not be distinguished from his twice-fired samples. Realizing that he had discovered a method of making electrical porcelain at a greatly reduced cost and by a much quicker process, he erected a small test kiln in the cellar of his home and continued his experiments with the one-fire process for two or three years, thus perfecting his formulas. On April 25, 1895, he organized and incorporated the Electrical Porcelain and Manufacturing Company of Trenton, the first electrical porcelain factory in the world to devote its entire production to the one-fire process.

The year prior to the organizing of the Electrical Porcelain and Manufacturing Company saw tbe first use of electrical porcelain for insulation against high voltages and it was the Imperial Porcelain Works of Trenton, N. J., who in 1894 made our first wet process high tension insulators. Mr. Fred M. Locke of Victor, N. Y., who in 1902 formed the Locke Insulator Mfg. Co. (now the Locke Insulator Corporation), also made wet process insulators about this same time.

Compared with our present insulators for high voltages these first attempts would probably be considered rather crude; but these first manufacturers deserve great credit for, although their product will not stand the criticisms of our present engineers, they laid the foundation of our great (operating and contemplated) electrical transmission lines. And when one considers that in the last 30 years operating voltages have increased from a few thousand volts to 220,000 volts their contribution to the advance of the electrical industry should be still more appreciated.


Machinery and Equipment


With but few exceptions the machines and processes used in the manufacture of electrical porcelain can be said to be adaptations from the general pottery practice. Of course certain manufacturers were pioneers in their introduction but ordinarily the fundamentals come from some other branch of the whitewares industry. This does not mean, however, that the electrical porcelain manufacturers were backward in this respect, but rather that their resourcefulness had to be expended in supplying the rapidly increasing and varying demands of the electrical engineer regarding size, shape and dielectric strength. And the pug mill illustrates this point very well for, although it has been the source of great losses ever since wet process insulators were first made, it is still the universal machine for forming wet process blanks.

As stated above some manufacturers were pioneers in the use of certain machines and processes and a resume of some of the most noteworthy follows.

The manufacture of wall tubes was at one time a tedious and expensive process but the ingenuity of Mr. G. F. Brunt gave us the machine which upsets the head of the tube so that today such tubes are very inexpensive. And to enable us to have tubes of most any length the Colonial Sign and Insulator Company in 1894 developed the suspension method of supporting them during the firing.

Glaze was at first applied by dipping the ware into glaze vats, but the unfired porcelain pieces absorbed the glaze so rapidly that a thin coating could not be obtained except by the most skilled dippers. Even then small holes in the case of dry process porcelain would become filled and time lost in cleaning the glaze out of them. August Weber of the Weber Electric Company tried spraying the glaze and found the method satisfactory. Today spraying of glaze is the rule in most dry process plants and some very ingenious automatic spraying devices have been developed.

In the manufacture of transmission line insulators the pull-down jigger was for quite a number of years the omega of development. With this machine one side of the insulator is formed by a plaster mold and the other side by a wood or metal template-the mold of course revolving on the jigger. It was about 1910 when someone (the credit for this innovation has not been determined) tried plunging a heated die into the porcelain mass in the mold. The steam formed by the hot metal in contact with the wet mixture acted as a lubricant and the price of line insulators dropped. Recently the use of metal to replace the plaster mold has been tried and the Pittsburgh High Voltage Insulator Company was the first to use the method in this country.

To the General Electric Company goes the credit of introducing to the industry two pieces of equipment and one process, all three of which were radical improvements over existing methods. These are:


(a) The Continuous Tunnel Kiln 1913

(b) The Casting Process 1914

(c) The Continuous Humidity Drier 1917


In the field of spark plug porcelains the practical use of the French Kneading Table was introduced by the Champion Ignition Company. This company also developed a method of applying surface combustion principles to a continuous tunnel kiln, firing glazed porcelains in open saggers to cone 16 (1917). In 1919, the Jeffery-Dewitt Company, now the Champion Porcelain Co., succeeded in successfully operating a Dressler type tunnel kiln continuously at cone 18, the highest commercial operating temperature for car tunnel kilns in America.

The developments in the field of electrical porcelain have in the past kept pace with the rapidly growing electrical industry. With this growth has come the feeling that technically trained men ace a valuable asset, and as there is every reason to believe that the ranks of the ceramic engineers will be kept full, the electrical porcelain industry in America should continue to produce the best electrical porcelain in the world.




Keywords:Jeffery-Dewitt Company : Jeffery-Dewitt Insulator Company : Greenwood Pottery Company : Electric Porcelain & Manufacturing Company : Fred Locke : G. F. Brunt Porcelain Company : Single-Fire : Pittsburg High Voltage Insulator Company
Researcher notes:Actual name is Electric Porcelain & Mfg. Co. (not Electrical).
Supplemental information: 
Researcher:Elton Gish
Date completed:September 2, 2007 by: Elton Gish;