Few people are aware that glass acts as an electrical Insulator. You’re not alone if you’re among the populace who didn’t know this interesting fact.

Glass insulators are currently gaining popularity in the valuable collectibles world. Collecting antique and vintage glass insulators is a fascinating hobby for several individuals, and the market is snowballing.

People who collect glass insulators give them sentimental worth, purchase them at auction, and display them on shelves in their houses. Glass insulators are among the most expensive collectibles, which could be one reason for this trend. Various factors influence a glass insulator’s value, including its quality, size, resistivity, transparency, and color.

This article describes the ten most valuable glass insulators and everything you need to know about them to prepare for an auction or collection.

A Brief History of Glass Insulators

The telegraph and telephone were the primary forms of long-distance electric and electronic communication for a long time before the present era of computers, cellphones, smartphones, fiber-optic connections, and the internet. Samuel Morse invented the electric telegraph in the United States in 1837, and in 1838 he sent the first message. Similarly, Alexander Graham Bell developed the telephone in 1876.

As time passed, networks of “open wire” telephone lines and later telegraph lines were created and constructed across the nation, and insulators had to be installed on these lines. Insulators were required to reduce electric current loss during transmission, but their primary function was to act as a means of fastening the wires to the poles.

Glass is a naturally occurring insulator, not a “conductor” or a “transformer,” as insulators are frequently mislabeled at flea markets and antique shops.

Both glass and porcelain insulators have been used since the invention of the telegraph. Still, glass insulators were more frequently utilized in lower-voltage applications since they were typically less expensive than porcelain.

The “heyday” of the glass insulator can be roughly attributed to the 1875–1930 period. During this time, many glasshouses—mainly in the East and Midwest—with a few plants in California and Colorado, produced hundreds of millions of these glass “bells.” In addition to making insulators, many glasshouses also made bottles, fruit jars, and other glassware.

Many of these lines were eliminated as technology developed over the 1960s, 1970s, and 1980s. Only a tiny portion of the glass insulator lines are still in use today compared to the height of open wire communication.

A Quick View of the Top 3 Most Expensive Glass Insulators

By the middle of the 1960s, collecting vintage glass insulators had become famous. Knowing which glass insulators are the most valuable isn’t only interesting; with this knowledge, you can wisely choose whether you want to sell or buy your insulators.

Let’s briefly highlight the top 3 glass insulators on our list regarding value. You can get a sense of certain essential glass insulators we’ll talk about later in this piece.

  1. CD 130.1 Cal Elec Works Glass Insulator (The Most Valuable Glass Insulator)

Valued at $6,000–$8,000; deep cobalt blue glass insulator. Collectors find this insulator particularly appealing due to its lovely color and unique design.

  1. The CD-141 Twiggs Insulator

Costs $3,000–$4,000. The size, clear glass hue, and unique design of Twiggs insulators make them highly sought-after. These insulators are tall — over 4 ft.

  1. EC&M, Cobalt Blue Insulator

Valued at $2,500; they come in many colors, but the cobalt blue ones are the most coveted.

10 Most Valuable Glass Insulators To Collect in 2023

Glass insulators were applied to telegraph cables in the 1850s, and glass became a common type of insulation for telephone and electric lines.

We’ve listed the most precious glass insulators in this guide. You’ll discover that the market value for glass insulators ranges from a few hundred dollars to several thousand dollars.

The following facts serve as the foundation for this analysis of the most valuable glass insulator:

  • Auction price
  • The available color
  • The specific type
  • The year of production

In the following paragraphs, we’ll go into more detail about these priceless glass insulators.

1. CD 130.1 Cal Elec Works Glass Insulator

CD 130.1 Cal Elec Works Glass Insulator

  • Auction price: $6,000–$8,000
  • Color: Cobalt blue
  • Specific type: CD 130
  • Year: 1870s

The California Electrical Works Company first used CD 130.1 glass insulators. These insulators were initially employed when building the first long-distance telephone connection in California between French Lake and French Corral in the 1870s.

Deep cobalt blue glass insulators make up the CD 130.1. Collectors find the insulator particularly appealing due to its lovely color and unique design.

The auction price of the CD 130.1 Cal Elec Works insulator ranges from $6,000 to $8,000.

2. The CD-141 Twiggs Insulator

The CD-141 Twiggs Insulator

  • Auction price: $3,000–$4,000
  • Color: White
  • Specific type: CD-141
  • Year: 1905

The Twiggs insulator is unlike the typical dome-shaped insulator due to its distinctive design. It has an exceptionally huge and narrower base, making it top-heavy.

Note: The dome is a rounded surface at the top part of the insulator.

There are only 13 Twiggs CD-141 insulator variants available now. You can see from this how unique this insulating style is. In addition to its distinctive design, this insulator has a slit at the top where two balls can be used to snag an electric or telegraph line.

The cost of the CD-141 Twiggs insulator ranges from $3,000 to $4,000.

3. EC&M, Cobalt Blue Insulator

EC_M, Cobalt Blue Insulator

  • Auction price: $2,500
  • Color: Cobalt blue
  • Specific type: EC&M
  • Year: 1870

In the mining districts of Nevada, California, Arizona, Utah, and even as far away as British Columbia in Canada, many of the EC&M insulators currently in the collection were utilized in telegraph and electric lines.

The ones in the best shape are the most expensive, particularly those around the skirt and dome regions. To have a decent market value, the EC&M insulator should have a few chips and cracks.

EC&M insulators usually cost about $2,500.

4. Cochrane Bell Suspension Insulator

Cochrane Bell Suspension Insulator

  • Auction price: $1,700
  • Color: Royal purple
  • Specific type: Cochrane bell suspension
  • Year: 1916

The Cochrane Bell got their names from bell-like shapes. These glass insulators in the form of bells were created by Harry Hamilton Cochrane and were patented in 1916. In particular, they were employed on the 131/2-mile, 65 KV line that ran from Corbin’s Bertha substation to the Porphyry Dike mine in Montana.

The purple hues of vintage Cochrane bells range from mild, nearly transparent, to rich royal purple and are remarkably elegant. These bell-shaped glass insulators are highly uncommon and precious because the majority of glass insulators have a classic shape.

Cochrane Bell Suspension insulators can be purchased for around $1,700.

5. Montreal Telegraph Co. Green Glass Canadian Insulator

Montreal Telegraph Co. Green Glass Canadian Insulator

  • Auction price: $1,126
  • Color: Light blue
  • Specific type: Montreal telegraph
  • Year: 1847

When it was established in 1847, the Montreal Telegraph Company was one of Canada’s early communications firms. Until the 1880s, the company used light blue glass insulators for their telegraph lines.

The insulators gathered between 1847 and the early 1880s are now rare but prized for their aesthetic appeal. Although significantly taller than the typical insulator, these Montreal Telegraph glass insulators have a milky tint when closely examined.

The Montreal Telegraph Co. Green Glass Canadian insulator costs about $1,126.

6. H.G. Co, Amber

H.G. Co, Amber

  • Auction price: $880
  • Color: Glowing yellow
  • Specific type: G. Co, Amber
  • Year: 1880–1930

Another popular item among collectors is the amber H.G. Co glass insulators. For daring collectors who aren’t afraid to try something new, amber glasses are as popular as deep blue ones. The tiny bubbles that provide pop and aesthetic charm to these insulators also make them desirable.

Amber H.G. Co glass insulators cost around $880.

7. True Cornflower Blue W.E. Mfg Co Insulator

True Cornflower Blue W.E. Mfg Co Insulator

  • Auction price: $835
  • Color: Cornflower blue
  • Specific type: Cornflower blue W.E. Mfg
  • Year: 1870

The first manufacturer of this rare-colored insulator was Western Electric Manufacturing. Genuine cornflower blue glass insulators are rare, making this one exceptionally unusual and expensive.

These insulators are the ideal addition to your collection or as an accent decoration in your workplace, living room, or bedroom. They have a light bluish color with a trace of green.

You can acquire the True Cornflower Blue W.E. Mfg Co insulator for $835.

8. Gregory Insulators

Gregory Insulators

  • Auction price: $700
  • Color: Aqua green
  • Specific type: Gregory
  • Year: 1903

The Gregory glass insulators came into the limelight in 1903 for use on the railroads in California’s Sierra Nevada Mountains and the Central Pacific Ocean.

This insulator includes a hollow that leads into the interior of the dome in addition to the dome-shaped top. Its consolidated design (CD) is prominently carved on the skirt’s side.

The auction price of Gregory insulators is $700.

9. DC 151 H.G.Co. NATCO

DC 151 H.G.Co. NATCO

  • Auction price: $300–$500
  • Color: Peacock blue
  • Specific type: DC 151 H.G.Co
  • Year: 1987

The DC 151 H.G.Co. Insulators were manufactured by the Hemingray Glass Company back in 1987. Notably, the North American Telegraph Company’s communication lines were equipped with these insulators.

Minnesota and Wisconsin are where H.G.Co’s glass insulators were first used, making up most of their origins. These insulators are now dispersed across the nation.

The peacock blue ones are the most sought-after of these glass insulators among collectors; their value ranges from $300 to $500.

10. CD-735 Mulford & Biddle Insulator

CD-735 Mulford _ Biddle Insulator

  • Auction price: $400
  • Color: Hues of aqua, teal, cobalt blue, and plain blue
  • Specific type: CD-735 Mulford
  • Year: 1840

The Mulford & Biddle insulator has an exceptional design that collectors adore since it resembles a pilgrim hat.

It’s a threadless glass insulator, which was common between 1840 and 1870, increasing its collectibility.

The first railways to utilize glass insulators were Mulford and Biddle.

The CD-735 Mulford & Biddle insulator costs about $400.

A Guide on How to Discern Glass Insulator Value

A Guide on How to Discern Glass Insulator Value

The content of this section touches on how to appraise and identify glass insulators before selling or collecting. Firstly, let’s examine what to look out for when ascertaining a glass insulator’s value.

Factors to Consider When Valuing Glass Insulators

As with other antiques worth money, glass insulators are assessed on several factors, as we’ll observe below.

  1. Age

Looking at the glass itself is a beautiful technique to determine the age of a glass insulator because glass-blowing technology evolved quickly along with improvements in communication technologies. While outstanding pieces most likely date from the mid-century, bubbling and a roughness to the glass may be signs of early molding if you can’t make out the CD (Consolidated Design) numbers.

  1. Rarity

The primary factor that determines whether a glass insulator is rare or not is typically its color. Light blue and transparent glass insulators were the most popular colors, although rich purples, greens, and other uncommon hues brought more fantastic prices at auction.

  1. Shape

The “beehive” shape was the most typical for glass insulators. However, finding insulators in other forms can be a helpful advantage.

  1. Condition

The insulator’s state can have a significant impact on value as well. Of course, the more damage an insulator has, the less valuable it is.

Insulators that show no evidence of melting, cracking, or staining will sell for the most money on the market, but those that show apparent wear and tear will have lower prices

  1. Demand

You’re ultimately at the mercy of the market with any antique or vintage object. How many people are collecting, as well as their hobbies, will significantly influence how much money your stuff will bring in.

  1. Manufacturer

Many collectors focus on specific characteristics of an insulator at the time of production.

Like with other antiques, the value of an item might go up or down depending on the manufacturer. The same is valid with glass insulators, as some collectors are willing to pay extra for an item depending on who produced it. Likewise, markings on glass insulators from less popular manufacturers might increase their value due to their rarity.

Antique Glass Insulator Identification

Since imitations of glass insulators abound, it might occasionally be challenging to find genuine glass insulators. Here, the following characteristics will allow you to tell a true glass insulator from a fake one:

  1. Design Number

Each distinct insulator design is given a design number in the hobby of collecting insulators. The CD (Consolidated Design) number is the identification numbering method that is most frequently utilized.

  1. Primary Embossing

Primary Embossing

Some embossed symbols on glass insulators represent end-user companies (or, in some cases, a brand name or set of initials used by the glass company). Still, they may be unable to identify the factory that produced the item.

These symbols are the insulator’s primary embossing (such as Hemingray, H.G.CO., Gregory insulator Kimble, etc.).

Hemingray-16 CD 122 is likely the major embossing on your insulator.

  1. Base Type

The area surrounding the insulator’s bottom outer circle (skirt) is known as the base. The kind of glass insulator is determined in part by this base type. Additionally, these base types aid in deciding the insulator’s auction value.

  1. Embossing

The embossing on the insulator key in identifying glass insulators once you’ve determined the primary embossing and base type. The insulator’s front (F-Skirt) and back (R-Skirt) are usually where the embossing is found, although they can also be found on the dome, crown, umbrella, or other parts of the device.

An EIN (Embossing Index Number) is given to each distinct embossing for a specific insulator design; it’s commonly shown in brackets, for example, (010).

Glass Insulator Price Guide

This section highlights the predicted market values for several glass insulators.

  1. The CD Insulators

The type of CD insulator you own will determine how much it costs.

A. CD 130.1 Cal. Elec. Works Insulator

This rare insulator retails for a whopping $5,000, which is significantly more than its competitors. The rich dark blue color enhances its beauty. This antique item is at the top of the list of the most expensive insulators in the world due to its distinctive design, rarity, and rich history.

The lowest price is $16.90, the highest is $7,500.00, and the average cost is $3,758.45. Best quality in comparison to comparable products.

B. The CD-141 Twiggs Insulator

Twiggs insulators are more in demand among collectors because of their distinctive form and clear glass color. The insulator is almost 4 ft tall and costs between $3,000 and $4,000 at retail.

C. CD-735 Mulford & Biddle Insulator

It’s a $400 threadless insulator made between 1840 and 1870 and discovered on railroads.

D. West Brookfield CD-145 Insulator

The Brookfield firm developed numerous insulators. The CD-145, which stands 4 ft tall and costs between $80 and $145 with the lowest price of $9.95, is the most popular and valued model of the Brookfield series.

E. WUP CD-127 Insulator

WUP is an acronym for Western Union Pattern, inscribed boldly on the skirt and has a teal-toned color.

It costs $15–$25 and is typically sold for $20.

F. Pyrex CD-128 Type Insulator

The Pyrex insulators were well known for having a better electrical voltage tolerance than the others. Large insulators were created for high-voltage electrical cables. As a result, only the CD-128 kind in the tiny size was ever manufactured.

It costs between $10 and $25.

  1. Hemingray Insulator

The type of Hemingray insulator you own will determine how much it costs, as expressed below.

A. Hemingray 45

This insulator has an unmistakable blue tint and is the product of years of experience in long-distance design. It was produced in mass quantities.

The Hemingray 45 glass insulator is valued as low as $1 and as high as $700.

B. Hemingray 42

One of Hemingray’s most well-known and productive insulators was the 42 (CD 154). It’s, in fact, by far the most sought-after insulator.

Most of these produced glass insulators are cheap, typically costing between $15 and $60.

C. Hemingray 40

A widespread and well-liked design—the Hemingray 4—was widely made in aqua and green. It was produced in large quantities until 1921 when it was replaced by the incredibly well-liked Hemingway 42.

The Hemingray 40 has an auction value of $1–$1,500.

  1. California Insulator

There are numerous rainbow hues available for this insulator. They’re crystal white, sage green, peach, plum, yellow, and purple. Sage green is the traditional color of California glass, which costs between $1 and $10.

Where to Find Antique Glass Insulators for Sale

If you seek where to sell glass insulators, various mediums provide an avenue to enlist your precious antique and vintage collectibles for sale.

The best platforms to buy and sell antique glass insulating include the following:

Auction Houses

Auction houses are your best bet if you desire untampered antique valuable glass insulators. Bill and Jill Insulators, Manifest Auctions, and Hanford Auction House are some of the most well-known auction houses for buying and selling glass insulators.


Rare antique and vintage glass insulators are widely available on eBay. The platform enables you to look through the list of glass insulators for sale, review their many details, and find additional images of the glass insulators that interest you.

Like an online auction, you can also offer your antique glass insulator for sale on eBay in the hopes that interested parties would contact you and make a considerable profit.


Etsy is an online marketplace that has grown in popularity because it offers a vast selection of goods for trade, including handmade, vintage, and antique items. The platform deals with antique glass insulators, but what makes it unique is its big market for these objects.

Flea Markets

You may also acquire or trade second-hand glass insulators in flea markets.


What’s the most valuable glass insulator?

The CD 130.1 Cal Elec Works insulator is the most valuable glass insulator. Its auction price ranges from $6,000 to $8,000.

How much are glass insulators worth?

Depending on the insulator’s age, color, maker, and quality, prices range from $2 to $400. However, the cost of extraordinarily rare insulators can be higher, up to $8,000.

Where can I find valuable glass insulators?

You’ll probably track down a small bunch of glass separators along railways in dissipated areas all over America and then some. These encasings are on electric shafts, inside the ground, or on train tracks. Be mindful to avoid having unintentional contact with power as you continue looking for these old-fashioned pieces.

Where can I sell glass insulators?

You can sell your collectible glass insulator on checked web-based stores like eBay, and Etsy, stroll-in second-hand stores, shops, swap meets, or craftsmanship focuses.

What are glass insulators used for today?

These days, old glass insulators prove to be valid. They’re utilized for enriching purposes in homes, for holding candles and blossoms. Assuming you find an exciting tone, you can put that on your rack to enhance your space.

Final Thoughts

After reading this article, we’re confident that you’ll appreciate how valuable glass insulators are. This applies to both collectors and those simply looking for information on them. Make sure your insulators are in decent or excellent condition, and you’ll see a rise in their market value.

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