Ask Woody

Reprinted from "Crown Jewels of the Wire", February 1987, page 38

I am most grateful to Mr. N.R. Woodward, Houston, Texas for his willingness to answer readers' questions. Mr. Woodward is the author of The Glass Insulator in America and developed the Consolidated Design Numbers identification system for glass insulators. Edward J. Trapp, a new collector from St. Joseph, Missouri, has submitted this month's questions.

ANSWER: There are four main purposes for numbers on insulators. First is the style number, as Hemingray - 42 and 45. This indicates the size and shape of the insulator and is for customer use in ordering, for cataloging and inventory.

A second set of numbers are shop numbers. These appear mostly on older insulators. Often they are large and crudely made, and can be on the crown or sometimes on the skirt. These were used as a means of identifying the product from one crew where a number of presses were feeding insulators into the lehr. After they came out of the lehr following annealing, the shop numbers enabled the insulators to be counted as they were packed. The crews were paid on the basis of how many insulators they made. The last use of shop numbers was about 1920.

The third and fourth set of numbers is mold and date code numbers. On automatic presses where there are a number of molds, a different number in each helps to identify the mold from which the insulator came if there is an imperfection. The date code numbers are different with different manufacturers, but most of them indicate when both the mold and the insulator were made. The 0-4: that you listed was used in molds during 1934, the first fill year of Owen-Illinois plant ownership. The two dots are for subsequent years, indicating that insulator was actually made in 1936. There is a mold number on the opposite half-mold. But different manufacturers use differing numbering systems, so it is necessary to understand each one separately.

Woody