Antique Glass Insulators and Their Electrifying History

Updated October 11, 2021
Old wooden telephone pole with glass insulators holds

Antique glass insulators are a low cost but very popular collectible that come in a myriad of fun shapes and colors. They're easy to find, and make a colorful, decorative display in your home, office, or business.

History of Glass Insulators

The first insulators had nothing to do with telegraph wires or electrical wiring and were used to protect homes against lightning strikes. However, these small glass cups were a vital element in the development of massive communication technologies as they helped telegraph and telephone wires keep their electrical currents from losing strength during their transmissions. This consistent flow of electrical energy allowed for speedy connections that simultaneously connected people around the world.

Industrialization and Glass Insulators

Glass insulators for wiring began to be manufactured in the mid-19th century in response to the needs born out of the technological advancements being made during the period. Samuel Morse had successfully used the first telegraph machine in 1844, and by 1850 telegraph lines were being strung from one coast of America to the other. Thus, the need for insulator technologies arrived.

As these communication technologies developed, with more complex wiring systems and larger amounts of electricity being fed through lines positioned close to people's homes, the historic glass insulator was retrofitted to be able to be used in conjunction with telephone and electrical wires. The first insulators of this type were small because they only needed space for one wire, but as time went on, the insulators became larger and reflected the growth in demand and power of these communication systems.

Glass Insulators

Rural Electrification Act

In 1936, President Roosevelt and Congress passed the Rural Electrification Act, which provided funding for rural areas to gain access to electricity and telephone systems through a public works project that sought to install electrical wires throughout the electrically free region. This surge in the number of electrical systems around the United States increased the need for the glass insulator and more companies specializing in manufacturing them sprang up as a response.

These glass insulators reached their peak use between 1920-1950. By the end of the 1950s, electrical companies had begun transitioning to porcelain insulators - a transition which was complete by the end of the 1970s. This meant that most of the insulators which collectors hunt down today come from the early-20th century. In terms of modern telecommunications, most electrical systems use cable, which doesn't need insulators at all, meaning that there's less of a need for these insulation technologies. Similarly, those that still require insulation utilize porcelain instead of glass as it's cheaper to manufacture.

Insulator Manufacturing Companies

There were hundreds of companies that manufactured these old insulators. In fact, glass companies like Indiana Glass manufactured insulators at the same time that they produced their highly popular Depression glass lines. Some of the manufacturers who produced antique glass insulators are:

  • Hemingray
  • Indiana Glass
  • Kerr Glass Manufacturing
  • Louisville Glass Works
  • McKee and Company
  • National Insulator Company
  • Owens-Illinois Glass
  • Pacific Glass Works
  • Star Glass Works
  • Whitall Tatum Company

Colors of Antique and Vintage Glass Insulators

Vintage Glass Insulator used on old lighting rods

As with most competitive industries, all of these companies produced insulators which had a slightly different design or color. The most common colors of insulators were clear and aqua; however, there were other colors and these ones can be quite rare and valuable. Some of the colors were:

  • Amber
  • Cobalt blue
  • Green
  • Two tone
  • Yellow green
  • Olive
  • Light blue
  • Purple

Old Insulators Made From a Variety of Glass Sources

Since the manufacturing companies didn't solely make insulators, they often used leftover glass from other projects to press a few insulators. Because of this, you may occasionally see an insulator in opalescent glass, vaseline glass, slag glass, or another unusual color (or even mixture of colors). These insulators are very collectible because of how rare they are. Other manufacturers recycled old bottles and other glass items, which resulted in swirls of color, bubbles, and other interesting effects in the insulator. According to a Collector's Weekly interview with insulator collector Ian Macky, cobalt blue is the most popular color among collectors.

Collection Glass Insulators

Beware Color Manipulated Insulators

Keep in mind that unethical sellers can alter the color of an insulator by applying heat or radiation and later claim that it's a rare antique and charge much more. It's difficult for even experienced collectors to discern the differences in natural and color manipulated glass insulators; so, it's best to be on guard against anything that doesn't seem right. If you are considering the purchase of an expensive insulator, it may be a good idea to have an experienced collector take a look and give an opinion on its value before committing to a purchase.

Glass Insulator Values

Old glass insulators can range in value from $2 up to over $400, depending on many different factors. Like other antiques, glass insulators are evaluated on several criteria, including:


Glass blowing technology rapidly shifted alongside communication technologies' advancements, meaning that a great way for you to parse out a glass insulator's age is by looking at the glass itself. If you can't make out the CD numbers, then finding bubbling and a roughness to the glass can be indicative of an early molding, whereas completely transparent pieces likely came from the mid-century.


Generally, color is the predominate factor that determines if a glass insulator is rare or not. The most common glass insulators were light blue and/or clear, with unique colors like rich purples and greens, bringing higher values at auction.


The most common glass insulator was made out of the 'beehive' shape, but finding insulators of different shapes can be a lucrative advantage.


Insulators without any signs of cracking, melting, or staining will fetch the highest values at market, while those with obvious signs of wear and tear are going to have affected values.


Ultimately, with any antique or vintage collectible, you're at the market's mercy. Whoever is currently collecting and what their interests are is going to have a significant impact on how much your items are going to sell for.


As with most antiques, the manufacturer can increase and decrease an item's value. Some collectors are willing to pay more just for an item based on who made it, and the same can be said for glass insulators. Similarly, having markings from less-common manufacturers can make insulators more valuable thanks to their rarity.

If you're thinking about buying or selling some old glass insulators, you're probably going to be looking at spending/receiving about $20 per insulator, give or take. On average, these glass insulators tend to sell for around $20, though there are special instances where insulators can sell for significantly more than that. Generally, the insulators that sell for more are rare, either because of their manufacturer or their color. For instance, this purple Canadian insulator sold for just over $85 and this unusual Merhson power glass insulator from the late-19th century sold for almost $90.

Electrify Your Decor With Antique Glass Insulators

Collecting and displaying antique glass insulators can be a low cost, enjoyable hobby. Electrify your decor with an antique glass insulator as these colorful bits of history can create a cheerful bolt of color and charm to any nook in your home.

Antique Glass Insulators and Their Electrifying History