Questions Answered by N.R. Woodward
by N.R. Woodward

Reprinted from "INSULATORS - Crown Jewels of the Wire", November 1970, page 6

Question from James Woodward III:  Enclosed is a sketch of a clear glass insulator I have found. Can you tell me anything about this insulator? I have several books, but none of them list this insulator. What is the approximate value of this insulator?  Any help you can give me would be greatly appreciated.

Can you tell me anything about this insulator? I have several books, but none of them list this insulator. What is the approximate value of this insulator?  Any help you can give me would be greatly appreciated.


This is one of the standard line of Pyrex Power Insulators offered by Corning Glass Works during the 1930's.
Their No. 441 was advertised for service at 50, 000 volts. It is shown as drawing CD 327 at the bottom of page 76 in "The Glass Insulator in America, 1969 Report."

From David D. Fredrickson of Arlington, Vermont:  

  Early Brookfield "pony" insulator, early 1880's.

Color aqua, seam large and over dome, threaded, embossed very faintly on dome:

PAT
JAN 25th 1870
JAN 14th 1879

J. William Gayner's mold, used at either Salem, New Jersey or Lynchburg, Virginia, but probably the latter, late 1923.

Color aqua, threaded with inner skirt, seam stops before dome, embossed No. 38-20.

From Keith, Elsie, Keith Jr. and Mark Ornbaum:  Could you or someone help us on the following two insulators we have found?

   FIGURE 1 - Found on the C. P. R. R. Aqua in  color, has mold line up to groove, flat collar; one has a "1", one has "111", and one an "X" on top of dome.

No information on these. This style was known as the American Union pattern. These were no doubt made by a small glass works, now unknown. They are found in the Midwestern States.

  FIGURE 2 - Found near W. P. R. R. Clear plastic with pink tint, has mold line over dome, no collar and three stress ridges on inside of skirt. Front - H. K. PORTER 106932.

This is a modern plastic insulator, now available from H. K. Porter (through distributors) as their No. 106932. This insulator has been accepted as standard for use in limited localities by both the railroad companies and 
Western Electric (Bell System). They were introduced about 5 years ago.

P.S. I have a suggestion from a collector friend, Charlie Halbert, here in the Houston area.  He would like to see you make a project of having your readers send in information on insulators that are not listed in my 1969 Report.  This would be styles under specific names, not minor color variations or extremely minor physical differences.  He would like to compile such a list as sort of a guide to the most rare insulators--on the assumption that if I don't have them listed, they are rare.  Believe me, this is not always the case--but anyway, I'm passing along the suggestion.  --- N. R. Woodward