The first insulators were a beeswax soaked rag wrapped around the wire. They worked well in the dry laboratory but soon broke down when exposed to the weather. The next concept was a glass knob, which looked much like a bureau knob, mounted on a wood or metal pin. From this evolved the pin style insulator which had no threading inside the pin hole. It was cemented to the pin by driving it down on the pin with a mallet on an asphalted rag. This was not a perfect answer because the weather worked on the rag and eventually the insulator would work loose and pop off the pin allowing the wire to contact a grounding surface. In 1865 a carpenter, Louis A. Cauvet, invented a method for threading the inside pin hole of the insulator which then could be screwed down on a threaded wood or metal pin.
Down through the years insulators have been made of many materials or a combination including glass, pottery, porcelain, adobe, metal, plastic, gutta percha, rubber, wood and composition. I am going to concentrate on glass insulators as they tend to be the most collectible. Obviously the earlier threadless insulators tend to be the most collectible and bring some of the highest prices. To date the highest price paid for a single insulator is $16,000.
The greatest number of collectors are in the United States and Canada but others are scattered around the world. Some collectors specialize in certain colors, designs, or even mold differences while others collect anything resembling an insulator. Glass insulators were made in many colors although aqua and clear are the most common. Colors include sun colored amethyst, royal purple, lavender, cobalt blue, peacock blue, ice blue, honey amber, root beer amber, emerald green, olive green, sea green, lemon yellow, puce, pink, steel grey and about every color in between. Being a utilitarian item, glass houses made them from whatever silica sand they had available. Most silica contains a certain amount of iron which gives glass an aqua blue-green color.
Early on clear insulators were very unusual as clear glass was expensive to make but by the 1920s it was cheaply made. Most modern clear insulators have very little value although there are exceptions. Only one out of about 50 insulators are of interest to most collectors. Often at most auctions a box of insulators will sell for two or three dollars which may be more than they are worth. But it's also possible to buy a box of insulators that may contain one or two worth hundreds of dollars.
Most libraries have a poor selection of books on insulators. For glass insulators Mulholland's Most About Glass Insulators or McDougald's two volume set, Insulators, are the best guides for researching. Both are purchased from the authors and are not sold in book stores. They may be accessed through the Illinois State Library System.
Both authors uses the consolidated design (C.D.) numbering system for designs which is important in identifying and buying insulators. McDougald also puts out an updated price list from time to time but you need the other guides to identify the insulators in the listing. There is also a monthly magazine called Crown Jewels Of The Wire. This is probably the single most important publication for the collector or dealer.
The magazine contains articles on insulator digs, research, lists coming shows in the U. S. and Canada, lists available publications and contains buy, sale and trade ads. A sample copy can be ordered from Crown Jewels Of The Wire, P.O. Box 1003, St. Charles, IL 60174-7003.
Next month's discussion will center on teapots. If you have questions or comments, please write "Collector's Corner," P.O. Box 1, Galesburg, IL 61402.