Porcelain as an insulator

THE DURABILITY OF PORCELAIN AS AN

INSULATOR.

BY A. B. DOBBS.

As an insulator, porcelain is a great deal tougher and more lasting than glass, and, while new, a higher insulation is claimed for it even when covered with dust and smoke. But in an experience extending over several years with all kinds of insulators, I have noticed that the glazing on the porcelain seems to crack when exposed to the weather.

A case of this kind came under my notice about two years ago. The original telegraph line from Montreal to Vancouver is strung on porcelain insulators of the same size and shape as the glass insulator, known in this country as the W. U. double petticoat pattern. Upon inquiry I was told that the porcelain insulators were not considered as good as glass (all the other wires on the line were tied to glass). I could see for myself that the wire in contact with the porcelain in many places left red streaks of rust upon it, proving that either the porcelain contained some deleterious substance, or that there was slight electrolysis, caused by leaks. The insulators were also seamed and badly cracked. In justice, however, I will say that the porcelain appeared to me to be of Canadian manufacture, which is of a very inferior quality.

It will be interesting to learn how porcelain insulators that have been in place from five to ten years have behaved; the record to include the condition of the climate in which they are worked and whether of American or foreign manufacture.

There is a growing impression, that for high voltages at least, porcelain is better than glass; but is it?