Ian Macky Explains the Colors and History of Insulators

August 19th, 2008

In this interview Ian Macky describes the origins, types, shapes and colors of collectible antique glass insulators. Based in Yreka, California, Macky can be reached via his website, Glassian, which is a member of our Hall of Fame.

Colbalt blue Hemingray

I got interested in insulators when I lived in El Cajon and my neighbor worked for San Diego Gas and Electric. His son had a bunch of insulators on the window sill in his bedroom. I had never seen them up close before and I really liked glass, especially glass that was found in places you wouldn’t normally see it, like on sidewalks or built into poles, things that glass wasn’t fit for. You always think of glass as being fragile, but it was used for some pretty industrial uses.

So I asked him about them and it turns out all the original insulator collectors were linesmen. They’d go out and do a job and there’d be an old pole with antique insulators on them. They’d swap out the old ones with the new ones and to everybody else, the old were just junk. So my neighbor knew a lot of other insulator collectors and it just went from there. There was a national insulator show in San Diego and even one in my hometown. It seemed like there were shows everywhere and collecting insulators was a common thing.

If only I had money then, I was just a kid and five bucks was a lot of money and ten was way over my price range. Now the prices have gone through the roof because once you get the common insulators, it’s time to go for the rare ones. They’re just so expensive now. I’d say 2 to 3,000 people collect insulators and half of them are really serious and still collecting actively. It’s all about supply and demand, and there isn’t enough supply, especially of the nicer insulators. If you like glass, there are some very beautiful colors of insulators, and people want those rare pieces of glass.

Collectors Weekly: What color and shape of insulators are the most sought after?

Macky: Most people, if they had to thin out their collection, would keep the color. In insulator circles, anything not clear or aqua is considered colored. Aqua and clear were the default colors. Because of the iron content in the glass, most of the insulators came out a little green, that’s the typical aqua color you see and it’s very common. It’s a nice enough color, but when you’re collecting you try to find everything but aqua. If you’re a CD (design-oriented) collector, you try to collect one CD in each style, you’ll find that most of your collection is aqua. Very few insulators were made in colors.

Most of the color is in a few of the styles, especially in the signal insulators that carried railroad signals. They were offered in colors by the factory, you could specifically order blue, amber, or green, which would be helpful if you had a pole with a lot of insulators on it, for marking certain circuits with certain colors. Otherwise, they didn’t try to make insulators in colors because it didn’t matter.

Amber Lowex

You’d get a few fancy colors because some glasshouse did a fancy batch of cranberry glass or made some colored glassware and had some left over so they pressed a few insulators with it. Most of the glass houses didn’t make only insulators, they’d make all kinds of glassware. That’s why you get fancy colors sometimes. If they had an order for a whole bunch of Cobalt blue candle holders and they had glass left over, they weren’t going to waste it so they would put it towards another glass item, sometimes insulators.

To make insulators they used a lot of cullet, or recycled glass, and every batch of glass has some form of cullet in it because it was a lot more workable. So depending on the cullet that was used, you’d get different colors. Sometimes you’d even get swirls if they didn’t mix it well. There’s a batch of very nice green insulators made by McLaughlin in Vernon, California. He got a truckload of green gin bottles and melted them down and created a batch of insulators. That’s where those nice deep green insulators come from.

Later on the manufacturers decided clear insulators were more practical because they attracted fewer bugs and heated up less. There were a few exceptions later on, when porcelain started taking over for insulators and they tried to duplicate the colors. There’s some black glass out there, which is pretty much late 1960s and they made white milk glass insulators which had a white porcelain look. But those were made later on and essentially those were just black and white to match the porcelain.

The most popular color among collectors is Colbalt blue. That’s one of the colors Hemingray offered for their insulators, there are thousands of them out there. But they are so popular they are all snapped up immediately, everybody wants them.

Collectors Weekly: Who were some of the major insulator manufacturers?

Macky: The biggest and best was Hemingray. They came along in a boom time when gas fields were being found, and cities would offer free gas supply to companies so they’d just follow the gas around. They produced the most different styles and were in production for the longest time. They made color insulators on purpose. They were also the makers of the Hemingray 42, the best selling insulator of all time, produced in the millions. You don’t see a lot of insulators in the air anymore, except at railroads, and they’re mostly Hemingray 42.

Purple Millville

Another popular manufacturer was Brookfield in New York. On the West Coast the only people making insulators were EC & M around the 1880s, which is pretty early. They made a really crude, bad insulator, but you didn’t have to ship it from the East. Those are very sought after now; they’re a unique style and a San Francisco product and they come in some very nice colors. But no one has any idea of who actually made them. There were plants all over the place, transportation and fuel were a big factor. You had to be close to a fuel source because of gas and the railroad and that was the market.

Some insulators were embossed with the manufacturer’s name and style number, and perhaps the year or mold number. The molds were engraved so the letters were dug in. There are a lot of unembossed insulators out there, but at the turn of the century there were a lot of engravers and glass makers and cast iron was very big so people were making a lot of molds, and embossing was very big. As the years went on, there were fewer engravers available and the embossing started getting simpler and simpler.

Collectors Weekly: During what time period were insulators used?

Macky: The very earliest insulators were lightning rod insulators. One of the interesting things about insulators is that they parallel the development of electricity. Before people were making electricity, insulators were being used to support grounding rods, just channeling electricity to ground, protecting houses. Later on when the telegraph was invented, suddenly there was a need to run wires on poles for many miles and to develop insulators. They started out small because there was typically only one telegraph line on a pole.

“EC & M made a really crude, bad insulator, but you didn’t have to ship it from the East.”

Then telephones took over and got popular, and there was the Rural Electrification Act, which tried to provide power to all these farm people. So there was a big insulator boom in the early part of the century, they were producing them by the millions. This was during the open wire days. From the 1920s to the 40s, that’s when the peak was. They started tapering off after that.

When I lived in San Mateo a lot of the old glass was still up in the air. There are some very thrifty companies out there, and insulators lasted and they just kept reusing them over and over. But today, if I walk around Yreka, there’s hardly any glass at all, usually for telecommunications they use cables, which don’t need insulators. For the power, they almost exclusively use porcelain. For new construction they will only sometimes use glass on the high power pylons. The glass ones are used a lot more in Canada than here. In other countries, it’s different, they actually use glass, but we use porcelain in America. I think it’s cheaper to manufacturer and mechanically they are a little stronger. The transition to porcelain started in the 1950s and by 1970 they were pretty much done.

Collectors Weekly: What were some of the early, rare insulator designs?

Colbalt Blue splotch Millville Kerr

Macky: The earliest design was used on the Morris telegraph and was called a bureau knob because it looked just like a knob on a dresser, just a knob with a groove in it. As soon as the first winter came along, they realized that design wouldn’t work. They discovered very quickly how important weather proofing was. The earlier designs had things called ram’s hooks, a hooked shaped thing down below and the wire would rest on the hook and they had to somehow insulate the hook from everything else.

There’s some crazy designs out there. One of my favorites is from Chicago. It’s claim to fame was that instead of having just a round shape, it had these diamond shaped depressions in it so when you ran a wire by it and tied it, the wire would only contact the insulator at a couple of points. Somehow they thought this was better insulation because the wire contacted the glass less, which was ridiculous. There were many designs like that, that made no sense at all. That’s what makes collecting insulators so interesting… all those rare experiments are out there.

Hemingray was very big on their drip points. At the bottom of their insulators they had these little raised points that were said to help the water drip off faster, so the insulator would dry off faster. I think testing has shown that it doesn’t make a lot of difference, but their salesmanship was good. After a while they got a bit more scientific with insulator designs and found out what exactly was important and became more standardized. That’s why the Hemingray 42 eventually became the main insulator and was the last generation of insulators. It worked well and they mass produced it.

When the phone companies would take down a pole, they wouldn’t save any of the insulators, they would just throw them in a hole in the ground. So there’s a lot of the old rare desirable stuff out there, been buried for years. But they’re glass so a metal detector doesn’t help. Usually the guys who find the old ones do a lot of research on where poles used to be and they’ll spend many years digging around. Every year someone comes up with a few new rare pieces. It’s fun to go out looking and digging. The best thing about glass is that it lasts a very long time if you take care of it. Insulators were meant to be outside so they’re weatherproof and survive really well.

Aqua threadless example

The rarest insulator I own is a Fry Glass insulator. It’s the same kind of opal glass they used on their tableware, called oven glass, because it did very well with heat changes. It was a popular kind of glass, but their insulators didn’t sell well. There are very few of them, but they come in a fantastic opal color. I come across a lot of rare colorations. My father gave me a Micky Mouse insulator in a milk electric blue. Most came in electric blue, but mine has so much milk glass in it, it’s almost opaque, and I think it’s one of the only ones out there.

I also have an insulator on my site that’s clear and has a streak of Cobalt blue through it. It’s more of an after market insulator. The guys who made it got permission to run a batch of Cobalt blue insulators, mostly for collectors. They got the machine set up and got something called frit, or concentrated pieces of glass used to get color into the new glass. They added that to the clear glass melt, but forgot to turn on the stirrer so they had clear glass with Cobalt splotches. It looks cool and people want them. I also have insulators on the site where someone got the mold, but not the press, so they took the mold and poured glass in it and just got a solid lump of glass. There aren’t many like that out there.

Collectors Weekly: What’s the difference between threaded and threadless insulators?

Macky: The very first designs they tried were threadless insulators, and they had to suspend the insulators with the hooks and the bureau knobs. Then they got the idea to put a wood pin in the cross arm and have an overturned glass on top of that, but at the time the hollow inside the insulator was smooth, there was no thread. So it was hard to get it to stay on the pin, they would glue them on. But it just wouldn’t stay on because it’s hard to make things stick to smooth glass. So they’d work in the summer but winter would come and the wires would shrink and tighten up and they’d start pulling and the insulators would pop off the pins. Finally around 1865 Lee Covey had the brilliant idea to thread the insulator cavity and have a matching thread on the pin and screw the insulator on so they wouldn’t pop off.

Collectors Weekly: Where do you find insulators for your collection?

Macky: There’s a national organization the N.I.A. (National Insulators Association) that puts on a national show once a year and regional shows once a year. There are also local clubs which host shows and activities at their houses. There’s a lot of activity, dozens of shows each year. That’s the best place to find insulators now.

Collectors Weekly: Is there anything else you’d like to mention?

Macky: I think collectors should collect only what they’re interested in. Don’t collect something because you think it will go up in value or collect rare things you’re going to stash away and never see. Whether it goes up or down in value shouldn’t really matter, you should enjoy your collection for what it is, and whatever happens you have something you like.

(All images in this article courtesy Ian Macky of Glassian)

96 comments so far

  1. sandra rathbun Says:

    i found a glass insulator back in 1984 on my property when we were digging to build my house i put it away because i thought it was the coolest thing i ever saw. woud you be able to tell me what year it was made. it is greenish in color but see through with the name amtel&tel co. on it . i realy would like to see if there are more of them out there.

    thank you

  2. Tony Anderson Says:

    Several years ago I found a threaded insulator buried in a road we were reconstructing. The town is very old in southern Oregon, 1840’s.The insulator is porcelain, single wire, a mottled dark to light brown and embossed with RED M. LOCKJ Victor N.Y. on the top.It’s in perfect condition, I can’t find even a small chip on it. I am curios as to the history and value if any. Any help you could be would be appreciated. Thank You for your time. Tony Anderson

  3. Burton Says:

    I have an insulator, I guess you’d say a light teal blue, rounded on top has a rim about 2/3 way down that goes all around and then a straight skirt down. It has the number 18 on it and the best I can tell it reads “Brookfield Cliffs NY”. Can you send me any info on this one? I cannot find it listed among other insulators. I’d appreciate any information or assistance.

    Burton Hatchett

  4. Burton Hatchett Says:

    I enjoyed your site!

  5. slag glass Says:

    I have what I thought was a small insulator. As I have a few. Only to find out my yellow & orange insulator…was not. It is a slag glass HouseX made for cars in the 1940’s used for ash tray. I would like to sell as I was told they are sought after. However I do not know how/who? I have posted on craigs list..however I just get junk mail in return. What do you think? Thank-you.

  6. Amy Erickson Says:

    I came across several of the wooden crossarm pins for the glass insulators and was wondering if they are worth anything?? Do people collect these?

  7. cal brown Says:

    I have a crackle red Hemingray -45 insulator…..didn’t know that they came in red, never seen one before. I wish to put it in our antique store but don’t have any idea as to it’s value. Can you (will you) help ? It is in perfect condition. Unlike other Hemingray insulators this one does not have the surrated bottom edge.

  8. A Morse Says:

    I have a V.G. Converse Patent May 2, 1893, Provo type insulator. It is 6 inches tall and almost 7 inches wide, bl aqua. It was my grandfather’s. he worked for the power company in our state. Is this an odd size?
    Best regards

  9. walter martin Says:

    i found a lite green h.g.co. insulator its about 4 1/4 tall 3 in on bottom does have a h on top do u know how old it is

  10. Wiregroove Says:

    The “V.G. Converse” embossed units are somewhat scarce. Most are aqua, and some are more blue (“Hemingray blue”). Most of the power units have nicks and chips due to their service as high voltage wire holders. If yours is in good condition, I would estimate the value range at 50.00-125.00 with the Hemingray blue’s being the more desirable.

  11. sam conant Says:

    Ian; Very interesting hobby you took up at an early age! I have a green insulator from the Lake Tahoe Ca. area. In an arc is: “PATD NOV 13th 1883″ Under this is: “FEB 12th 1884″ Near the top is “08” Not sure if it is a true 8. I am not so much interested in value as I am in the history. Any thoughts you can send my way would be greatly appreciated. Thanks! Sam Conant

  12. Robin C Says:

    I have 2 cobalt blue porcelain insulator, one has Locke 44 and the other has a B inside 2 circles. Can you give some info on them. Thank you, Robin C

  13. Ian Says:

    Whoa! Didn’t know all these comments were here. I wasn’t ignoring everyone, honest. I just got an automatic eMail today telling me there was a new comment (#12) but it never did that before for the previous 11!

    1. sandy: Without seeing a picture, it’s hard to comment on your piece, but it’s likely a “toll” insulator (CD 121) which were used during the big expansion of long-distance (“toll line”) open-wire telephone networks. If that’s what it is (and “AT&T” emobossing occurs most often on tolls), it dates from around 1920. There is a picture of a toll insulator here: http://glassian.org/CD/121/121.html

    2 & 14. tony & robin alas, I don’t really know anything about porcelain insulators– I just collect glass. I suggest you check out http://insulators.info, and perhaps send a message to the ICON mailing list– there are plenty of “mud” collectors there who might help.

    3 & 4. burton: glad you found my site interesting; but it’s hard to tell what you have from the description. Did you check my “CD” (Consolidated Design) gallery? Assuming it is threaded (in the pinhole), most of the known Brookfield CDs will be shown here: http://glassian.org/Gallery/threaded.html

    5. slag glass: There is some information about your slag glass ashtray (which looks just like an insulator, and was likely made by HouzeX Glass Co. or Akro Agate) here: http://www.nia.org/notins/nons1a.htm

    6. amy: Wooden insulator pins are desirable if in good condition, and especially so if unused, but they are not a high-value item. Insulators were made by the millions and each insulator had its pin, so there were a LOT of pins made. Some people do specialize in insulator hardware (hello Lou Hall!), but the basic straight pin is not unusual. They are very useful for screwing insulators onto, however, so maybe you ought to be thinking Outdoor Insulator Display!

    7. cal brown: Your crackle insulator was made by heating an insulator in an oven then rapidly cooling with water to shatter it. In doing this, the insulator is essentially ruined and loses whatever value it had. However, the crackling does catch the light nicely, which is why it’s done. Fortunately, it’s the common, modern, clear insulators that are usually crackled (and the Hemi-45 is relatively new and inexpensive), so no real harm done. No insulator was ever made in a true red, so the coloring is likely either glass paint or some sort of fired-on stain. Value: worth most to you since you like it.

    8. A Morse: Your insulator is a CD 283: the dimensions match. It’s a nice power piece, and especially nice that it came down through the family. There are several style of “Provo” insulators (the CD 283 is “No. 1″, the middle size, then there’s the smaller CD 282 (“No. 2″) and the largest, CD 249 (“No. 0″). A #1 in good condition is probably worth in the $50-100 area, or perhaps more depending on the color.

    9. walter martin: Hemingray Glass Co. used the “H. G. Co.” embossing during their earlier years, probably prior to 1915 or so.

    10: Wiregroove: You beat me to it, thanks.

    11: sam conant: Your insulator is a CRown Embossed Brookfield (“CREB”) from New York, ca 1880s or so. It should have more embossing, including a street address, which would help pin down the date. Crown embossing was difficult and wore out quickly, so they switched to skirt embossing in the later years. You can see more here: http://www.insulators.info/articles/cd_145_creb.htm


  14. Monica Says:

    Great article. I just purchased some blue insulators and want to use them in a art piece I am assembling. I will use these insulators for their beautiful color and I want to put tea light candles in them. I need to know if this glass can withstand the heat from a candle directly or a tea light candle? I bet you know the answer…….Thanks, Monica

  15. Mike Herron Says:


    Insulators can have a variety of functions after their original use, and I have seen them used as candle holders many times. The heat will not damage the insulator, as it would have to get extremely hot to cause it to break. However, be careful what insulators you use for candle holders, you may have common insulators or some that are quite valuable!! Find out what you have before you make such use for them!!

  16. Ian Macky Says:

    Monica: insulators are fully annealed at the factory and are able to take quite a bit of heat shock– at worst, an insulator that’s hot from sitting in the full sun might get soaked with cold rain– but I’m not sure about a direct candle flame. Unlike toughened suspension insulators, regular pin-type insulators will break into very sharp pieces. You’ll have to research for yourself what sort of glass is suitable for a tea light, I can’t give a definite answer. Sorry! –ian

  17. Robbie Dixon Says:

    Love this info !! I started collecting insulators when I was very young.We lived near XX-tracks, and my buddies and I walked them daily. I probobly had a hundred or so of the glass insulators.Got older,more worried about girls and such than anything else.they got put up in my parents attic, I moved out,got married,and my insulators got moved with my parents a couple of times until they moved to the country here in Florence,SC.They chuncked them in an outside shed that was falling down,and I did’nt see them again until now.All I have left(so far that I’ve dug up,some under the dirt where shed was) is 20 each. 4 or 5 are chipped bad,but 15-16 are in great shape.I’m kicking myself in the butt for not taking care of them,but then again,i’m 45 years old, and if I would have kept alot of things I had when I was little, I would’nt have to work again.Who knew?I see the insulators going for $10.00- $20.00 each on the web,and it breaks my heart.Most of mine were clear,light,or dark green.But they are beautiful are’nt they!

  18. Ian Macky Says:

    Robbie– the RR right-of-ways is where you will still find a lot of insulators today– most of the ones still in the air. They carry RR switching signals– or used to– mostly they’re defunct now, but RRs often don’t pay to wreck them out so there they sit in the millions. There are a lot of Hemi-42s and more modern glass. Not so much in pretty colors any more, but still lots of aqua stuff that’s 100 years old.

    The glass I collected as a kid went into a box when I left home (wrapped nicely in paper, not chunked!), and stayed there until I bought an old house (1905) that had real windowsills. Then I took them out and put them in the sun and remembered why I had collected in the first place– got hooked again.

    They’re weather-proof! Even if they’re not worth much, they look great out in the yard or on a fence, catching the sun– or inside on the windowsill (if you have a deep enough one).

    If you learn a bit a history you can tell when/where they were made: Brookfield:New York, McLaughlin:Vernon, etc. Impress your friends!

    There was a 100-year-old Brookfield on the pole outside my San Mateo, CA house– when they switched the glass out for modern stuff, the lineman gave them to me (I just happened to be there at the right time). It was a long way from home, and old old old, but still useable, and still beautiful.


  19. Cobalt blue Hemingray Insulator Says:

    Ian, I love your article. My husband and I are unpacking some old items he has had since a little boy in the Texas Panhandle, Borger, Texas.
    He has at least 3 insulators. One Cobalt blue Hemingray Insulator, one clear, and one aqua. What do you think the value of these are?
    I would not want to sell them, just curious. They bring back my childhood days of walking the railroad and looking up at those beautiful old insulators. I always knew they were beautiful, and they are even more so now since I’m 60 this year….
    Thanks again for such a good article.

  20. Ian Macky Says:

    Hi Eileen…

    Cobalt blue is a very popular color since it’s just such a rich a beautiful shade. Cobalt Hemi signals were made by the thousands, but they are so popular and desireable today that their price is well above what it would be if judged by rarity alone. Depending on the condition, it’s probably worth in the $200-$500 area– assuming it really is cobalt blue and not a wimpier shade.

    Hemingray had a “factory color” called by collectors, unsurprisingly, “Hemi blue”, but that’s not at all like a cobalt blue and is much more common. Without knowing more about your clear and aqua insulators, there’s no way to comment on them. You can email me pics if you want to ian at macky dot net.

    Love those cobalt blues! After the Hemi ignal, the next most common/affordble cobalt blue insulator is an EC&M, which sells for $2000-$3000 (I don’t have one, wish I did). Too bad there aren’t more insulators in that color, it’s oh so very nice.


  21. bill curtiss Says:


  22. Alison Says:

    Wondering if there is any way to remove small burn marks on inside. Best way to clean? Helpful info here – thanks.

  23. Ian Macky Says:

    Alison– not sure what you mean by a burn mark. Do you have a picture?

    Good instructions for cleaning glass are here: http://insulators.info/care/cleaning.htm

  24. Alison Says:

    Was wrong about burn mark – apparently it is good ole grime. Brillo pad took most of it off. Will perhaps try oxalic acid solution for more stubborn spot. Good to know when collecting that this comes off. I often eliminated them in antique shops for how dirty they were. Thanks for your help.

    Question: do air bubbles make them more or less valuable? I think it makes them more interesting.

  25. Ian Macky Says:

    Alison: I highly recommend oxalic acid. You just stick your glass in a covered bucket of the stuff, wait 24 hours, give it a light scrub and it’s sparking clean. Do not use on carnival glass or soft glasses! Read the cleaning insulator article carefully before trying this.

    As for your question, *anything* unusual about an insulator usually makes it more valuable. Bubbles, snow, potstones, inclusions of any kind, overpours, underpours (especially hare lips), contrasting colored streaks, milk, ghost embossing– anything which makes it stand out from the common crowd is good.

    For rare insulators, not so much– people might be more interested in a clean example. But for more common insulators, unusual is a plus.

    In particular, bubbles are good. Big ones, millions of little ones, go go bubbles! The only kind of bubble which is not so good is an “open bubble”, where the bubble has risen to the surface of the glass and popped, but the glass was too cooled and stiff to fill in the hole. So now there’s a open sort of pit on the surface, usually with sharp edges… not particularly nice and not going to improve the value.

    I have a Hemingray-42, *the* ubiquitous insulator, worth almost nothing usually… but this one has a nice shiny nail right in the front skirt just behind the HEMINGRAY embossing. Very unusual. Price without nail: $0 (unsellable). Price with nail: $500

  26. Alison Says:

    Very interesting info. Thanks!

  27. b Says:

    I have a aqua Hemingray 9 and was wondering how old it is.

  28. Ian Macky Says:

    The Hemi #9 is a “pony” insulator from the era of open wire telephones, ca 1930 or so. What is the exact embossing? There may be a date code on it.

  29. cameron boyett Says:

    enjoyed your site I have 2 barrels full of old insulators, most from late 1800’s looking for someone interested in them

  30. Ian Macky Says:

    Cameron, how were you able to date the insulators? They are expensive to ship in quantity, so you might be best off bringing them to the closest show or contacting a collector in your area. has a show calendar, and you can search for collectors here . Do you have a picture?

  31. Lynn Bishop Says:

    I am so excited and amazed at the different types/colors of insulators! I love glass and with in the last 10 years or so I have collected several insulators. These are the regular aqua and or porcelain ones. But my baby is a small 3 inch tall aqua little guy. It’s a Hemingray #9, made in USA, patented May 2, 1893. It’s the oldest one I have. I am currently making craft items using them but I won’t use my baby. Can you tell me what you think it’s worth?

  32. Chuck Stellick Says:

    I have a large collection of insulators. I am interested in selling some of them. I am in Alberta, Canada. I can send pictures if you like. Can you give an indication of prices?

  33. Ian Macky Says:

    Chuck– sure, send some pictures to ian at macky dot net and I’ll see if I can help. Please, not too big! I’m still in dialup. Insulators are expensive to ship, and of course fragile, so it’s often not worth sending entire collections. I could also help you find someone closer (I’m in California). –ian

  34. Ian Macky Says:

    Lynn, your little Hemingray is alas not terribly valuable since they were made in great numbers, mostly in aqua, but it’s a nice piece of history and looks great in the sun. In fancier colors it would be worth more.

    Aqua, although pretty, is the most common color in old insulators since the iron impurities found in most sand (the main ingredient of glass) causes the greenish tint. Glass colorants are generally metals or metal oxides. It’s difficult and rare to find sand *without* iron, which could be used to make clear glass. If you make up a batch of glass out of any old sand (plus flux, etc) it will almost surely be aqua.

    Your piece most likely carried telegraph or early open-wire telephone signals. The patent date refers to the “drip points” on the bottom, a dubious Hemingray invention that was supposed to help the insulators shed water faster.

  35. Melyssa Says:

    I have an aqua Insulator that reads “Brookfield New York” and when I look straight down into it I can see the number “5”. It came with a gold colored wood cross pin that has three heavy metal prongs that it stands on. Can you please give me some info on this one? I would really appreciate it! Thanks!

  36. chris Says:

    I have an old insulator with C.S.A. embossed on it is this from the civil war time frame? If so is it a valuable piece?

  37. Ian Macky Says:

    Melyssa’s Brookfield looked like a “BGM blot” CD 162 (signal) to me– I told her so in private email. See a bit about BGM, and a gallery of their insulators, here:

    Chris: CSA is one of the modern styles, ca 1930s: C = “Carrier circuit application” and S = “Steel pin”. They were made in clear, borosilicate glass by Hemingray, Corning (Pyrex), etc. As a newer insulator made in large numbers, it’s not very valuable.

  38. Billy Says:

    I also have a “Brookfield New York” with the number “5” reversed on the top but it seems to be more of a darker green color then the pictures on the BGM Blot page. What can you tell me about this? Is it too a BGM Blot? Thanks!

  39. Thomas Cappel Says:

    I have a large light blue insulator which I believe went on top of the pole.
    It is about 10 inches wide with a double collar underneath. The only identification is a 32 in dark blue on the top where the wire would go.
    What is it?

  40. Ian Macky Says:

    Billy– I answered you in private email, hopefully you got it. I’d need to see a picture to comment on that insulator– Brookfield made a LOT of styles.

    Thomas, is it glass? Send me a picture to ian at macky dot net and I’ll see if I can identify it.

  41. Eric Says:

    i have 6 hemingray insulators. one is clear no. 17.. 2nd one is clear no. 42 whith a 0 under the company name. the 3rd one is brown lowex no.660 with 5-8 under the made in usa. the 4 th one is no.40 on it. 5th one is no.42 on it both are blue green color. the 6th one i have is like a light blue with H.G. Co on it thats the only markings it has. i was wanting to know more about them. thought about selling them. thanks Eric

  42. Christa Black Says:

    I purchased a black insulator recently. However, this one is not made of glass. I am not sure what it is made of, there is no markings, of any kind on it, the copper wrapped wire is still attached and it is a threaded but I am guessing that it is a heavy rubber?? How do I find out what and how much and who made it? Thank you.

  43. Ian Macky Says:

    Christa– it’s probably hard rubber. Some of the early ramshorn-type insulators used hard rubber, as did more modern replacements for glass. Rubber is damage-proof, but perishes in the weather. There’s pro’s and con’s to everything! New ones, usually made by Continental Rubber Works, are not worth too much, mostly because they just aren’t too pretty compared to the colored glass and glazed porcelains; ramshorns and any old pre-pintype insulators are always valuable. There is a bit about them at the NIA site (with pics):

  44. Rodger Epley Says:

    I have found in a barn sale in perfect condition a bell shape 4″ WHITE insulator that is stamped on the side the numbers 29 and 119. Threaded inside. Unable to locate any information. I see the color white is almost unheard of. Thanks

  45. mike perry Says:

    I found a glass insulator in North Georgia (a Hemingray CD 120 R-Skirt style) patent Dec 19 1871 with a second patent date on the reverse side of May 2 1893 with a “5” above the date. There is no name of manufacturer and the color is Aqua. Can you direct me to more information on it? or tell me more about its history and possible the value? Thanks in advance for you help.

  46. Ian Macky Says:

    Rodger– sure it’s not white glazed porcelain? The only milk glass insulator in the US was the Maydwell-20, which was made to blend in with the porcelain ones (glass was on its way out at the time).

    Mike– your CD 120 is surely a Hemingray product; the 1871 patent date is for the threading, and the 1893 patent date is for drip points (a Hemingray invention). This is an old style, telegraph era; aqua is the usual color– worth around $20 in that color I’d guess.

  47. Tammy McLaughlin Says:

    I purchased a light blue McLaughlin glass transformer and six others with different names that do not have patents from a thrift store today. The McLaughlin transformer has a patent number of 20. My grandfather on my fathers’ side of the family John McLaughlin was an electrical engineer through Edison Electric at Chicago, Illinois. Do you know any information about this item? I would appreciate any responses.

  48. Ian Macky Says:

    Tammy– your McLaughlin was made in Vernon, California somewhere between 1922
    and 1935 by the The McLaughlin Glass Company, a small family operation that is well
    known on the West Coast. The “20” refers to the style#– I don’t think that pattern was

    The elder McLaughlin (William) worked at Robert Good, Jr.’s glass plant in Valerde, CO,
    and later the Illinois Glass Company, Illinois Pacific Glass Company and the Southern
    Glass Company in Los Angeles, before starting his own plant.

    In collecting circles, Fred Padgett is the McLaughlin man, and he wrote the book about
    McLaughlin called “Dreams of Glass”, which I don’t have handy or I’d tell you more!


  49. Ryan Says:

    Just found 4 buckets of these hemingray insulators in different sizes and colors including green, blue, clear and looks like porcelain off white one with just one marking thy looks like a B surrounded by a circle? Don’t know what they are worth or what exact year found in a barn of an old family of electricians house. Any ideas??
    Hemingray 42,20,19 to name a few… Most of them in new condition few have chipped teeth or threads. Any help is much appreciated.


  50. laurie moulton Says:

    I found this aqua green insulator at a yard sale. It has no threads or markings on it. It is seamed. Glass is loaded with bubbles. It has a flat top. Can you please help me to identify this?

  51. Ian Macky Says:

    Ryan– Can’t help you with porcelain, I don’t collect it or know much about it.
    In general, clear glass is the most recent and colored glass is older. The big
    wave of insulator production was in the 1910-1930 era (REA, open wire toll
    lines, etc). Hemingray insulators often have the date of manufacture on them,
    usually as a number NN-MM:: where NN is the mold# and MM is the date, with
    each additional dot following the date adding another year. *Probably* not
    worth too much– the common insulators are *very* common, especially the
    Hemi-42, the most ubiquitous of all insulators. Would need to see pictures
    to be sure though.

    Laurie– Can’t tell from your description what you’ve got. If you post the picture
    somewhere I can see, maybe I can ID it. I love the whatzit? game so let’s see
    that pic! You could also email me a pic to ian at macky dot net.


  52. Joe Wallis Says:

    Laurie, Your insulator sounds a lot like a CD-731 produced in the 1860-70’s.

  53. Pauline Says:

    I found some aqua Whitall Tatum Co #1 with a number 39 on it and some green Whitall Tatum Co #1 with a number 2 on them clear one don’t understand the writing on it but has the numbers 90 & 49 on it. Can you tell me more about them?

  54. April Says:

    I have recently came across an insulator clear glass with hemingary #60 was wanting any info about the date and the value thank you ….. April

  55. Ian Macky Says:

    Pauline, your WT #1 are CD 154s, the penultimate general purpose insulator design, and were produced at the end of the telegraph era. The ultimate design is the CD 155, which looks the same except for having a heavier shoulder to support the weight of the wire. The numbers (39, 49, 90 etc) are mold numbers; molten glass is very caustic and eats up molds, so they have to be replaced regularly. Looks like WT went through at least 90 molds for their #1. The most common CD 154 is the ubiquitous Hemingray 42, but many manufacturers made this style (which was copied by “foreign” companies in Mexico, South America, Spain, etc). The WT #1 comes in a nice purple also, and is the most common purple insulator. But being purple, it is desirable, since who doesn’t like purple glass? Clear, aqua, etc are more common and less desirable, so are worth less. Also comes in a nice pink!

    April: Hemingray #60 is known as a “mickey mouse” insulator because of the large ears. It is a power insulator rated 6,600 volts, and was meant to carry a cable (i.e. a covered conductor, not just a bare wire). The cable would lie in the top groove, and was attached in place by a tie wire wound around the ears. They were made from about the teens through about the forties. Your might have the date of manufacture on it as a 2-digit number (possibly followed by some dots, each dot being an additional year; i.e. 30::. would mean the mold was made in 1930, then a dot was added each additional year it was used, so with 5 dots that’s 1935).

  56. Auto Glass Removal San Francisco Says:

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  57. Kathy Crowther Says:

    I just posted a picture on show and tell of what was labeled as a Vintage Insulator when I bought four of them. It is pressed glass. There are alternating blocks of diamonds and flat pieces. The bottom looks like a flower design. There are a lot of small air bubbles. It is not marked.
    Please help

  58. Ian Macky Says:

    Kathy: definitely not insulators. They look like votive candleholders to me.

  59. Jackson Says:

    I still find them along old and abandon roads and rail lines up here in BC, a few hours drive from Vancouver. Along Hope and sometimes in Maple Ridge and up through the Fraser River area before Hope. I’ve found many a rare piece, and there’s 1000’s of them just lying there, some on downed poles, some on the side of the roads and quite a few if you look hard enough in the bush where the old roads are now grown over

  60. sherry patterson Says:

    We have a whitall tatum clear glass insulator that still has the wooden insert in it and wonder what it might be worth it is in perfect condition

  61. Ian Macky Says:

    Sherry, depends on which one you have. The common styles were made in the millions and are worth $0 to a collector, but have some value in just being historic and looking nice on a windowsill. The rarest W/T style (in clear glass) is worth $10,000. All but the rarest one (which I don’t own) are shown in my Millville gallery at

  62. kari Says:

    i was hoping you could tell me a little about an insulator that is a frosted clear type of glass that is a young southern bell dressed in a bonnet and a long southern dress a set of two.I can not seem to find anything about them,any information will be helpful,thank you

  63. Lori Shewmaker Says:

    I have found a very large light blue insulator I think it’s porcelain. It must weight close to 10 lbs. It is dated Aug 1929 with an arrow pointing up in front of the date. In a darker blue looks to be a stamp

  64. Sam Owen Says:

    Ian, hey get back here, we’re not done talking about insulators!

  65. Helmut Kaiser Says:

    One can still find old insulatos popping up at garage sales. Two days ago, I picked up a CD145 Milk Glass Insulator. Granted, it’s unmarked, but it’s great
    condition and still has the soot on the inside and drip-edge. I assume that it spent years in service sitting on a pole and holding up a cable.
    I paid the extravedant sum of $1.00 for it.

  66. Kami Says:

    I found an insulator at a sale in a storage unit it is Brookfield light aqua or light green can’t really tell which one. It has the letters OX on the top with 2 indents and the bottom has what looks like teeth. Do you know the year it is, what it was used for, and what it might be worth? thank you

  67. Barbara Says:

    I found a big yellow glass insulator with a copper ring on the top. Around the bottom are the words made in America O with a mark in the middle, 14 50.
    A/’///St/’0//g’s DP I And it is full of cracks but not broken. I cannot find any information on it at all. Can you help me?

  68. Rena Berube Says:

    I want to buy clear insulators to make shade for my light, i need 5 ” long, i do not know by the numbers the size. I see a lot for sale on the internet but i don’t know the scale. Please help, thanks.

  69. Karen Anderson Says:

    I saw something that I havent a clue what it is or could be.
    First thing I thought of was insulators when I saw them. They are much shorter tho. There are 3 differnt ones each a different color. All are connected. An between each one is a
    a bell shaped weight that says per 10000 lbs. Do you have any idea what this could be? If not soon as I get back to my friends I’ll get a photo of it and post.
    Any information would be greatly appreciated. An I really like all the information you have shared.
    Thank You,
    Karen Anderson

  70. Barb Grobe Says:

    I bought a WHOLE bunch of glass insulators by various manufacturers at an estate auction a couple of years ago.
    Out of that bunch, there was a good sized box of what I would classify as “culls”, with chips or chunks taken out of them…
    I would LOVE to break these insulators down into small pieces/chunks and glue them to the outside of a frame and put a mirror out of it…what is the best way to go about breaking them?
    Also, in the same bunch, were several black, hard rubber insulators…are those common? Are they insulators or covers for insulators.
    Thanks for any information you can give me and I’m sorry if I have caused any of your readers to go into a “panic” mode with the thought of me breaking up a bunch of insulators…believe me, I have plenty nice ones for display, craft items, etc.

  71. Ian Macky Says:


    Just because an insulator is damaged does not mean it’s worthless. The rarer something is, the more forgiving we are of damage. I only have heavily damaged examples of a few rare pieces, sometimes only half an insulator! I paid $100 for a Pomona center, with the entire skirt gone, and was happy about it. So make sure the things you want to smash are really worthless.

    People “crackle” insulators by heating them in the oven, then putting them in a sink (covered with a cloth) and pouring cold water on them. The rapid temperature change fractures the glass, but you will end up with small pieces. I’ve never tried breaking insulators on purpose. Some of the older ones are very fragile (not annealed well), and it doesn’t take much at all to break them– harsh language suffices– but others are surprisingly tough. If I was going to do it, I’d probably place them in a box (to restrain flying fragments), wear gloves and very good eye protection, and whack them with the peening side of a ball peen hammer. You might also knock the tops off first by turning them upside-down and hitting the top of the pinhole with a punch (hammered). The rest would be easier to break then. But no matter what you try, know ye this: glass breaking is dangerous so be very careful!

    The hard rubber insulators are uncommon, but not very desirable, so not very valuable. Few collectors are into non-glass non-porcelain insulators. Hard rubber was used in some very early ramshorns and other styles, but you mostly see them as more modern unbreakable replacements (along with plastic types). There is a 1975 book named “Unique Collectible Insulators: Non-Glass, Non-Porcelain, Wooden, Rubber, Composition, and Metal” that probably shows your rubber insulator.

  72. Helmut Kaiser Says:

    I recently dug a Dark Green CD731 in New Brunswick NJ.
    Was tottaly surprised to find it. I was metal detecting in the riverbank
    and dug an Indian Head Penny and got the insulator as a bonus!
    I will post a photo.

  73. Murray Storrings Says:

    Great site as a collector found this site very interesting and the information great for collectors of glass insulators

  74. Susie Says:

    I stumbled across your site while doing a bit of “pre-purchase” research. My etsy.com cart contained 12 items totaling almost $300; all insulators. I was skeptical about the wonderful array of colors being offered, from yellow to glowing orange, emerald green, cornflower, sapphire & ice blues, royal purple, deep pink, sapphire pink, the list just goes on and on. Most were offered at $15 or less, with a couple in the $35 range. Am I right in being skeptical of these items? Almost all are in excellent condition. The old saying comes to mind, “if it seems too good to be true, it probably is!” Thoughts??

  75. Ian Macky Says:

    Hi Susie. You are right to be cautious– there are many fake insulators out there now. Mostly they are common insulators, usually clear ones, that have been painted with (baked on) glass paint or stained– colored fantastically. Sometimes they are irradiated, though the color palate produced by irradiation is much more limited. Even the commonest, cheapest of the real colored insulators sells for more than $15, usually much more. You should ask the seller if they have been altered in any way. It’s not kosher to sell “fake” insulators as real. On eBay right now there are almost 100 stained insulators for sale, usually priced from $10 to $15. They are worth $0 as collectibles, but do have some value as pretty things to put on a windowsill– however your money would be better spent on the real thing. –ian

  76. Cindylou Says:

    I’ve been collecting insulators for some time now. I came across one that’s made with mud, cly, and or adobe. It has no glass. It looks like just a mud insulator, threads and all. I would just like to learn when , where, and what they were used for. If anyone has any idea of its value, I’d like to know that as well. Thank you!

  77. Ian Macky Says:

    In general, that type of insulator is called “composition”, and there are many styles, the most common of which is the “Arizona beehive”. Is yours the classic beehive shape?

    They were used in the southwest where there was very little rain (otherwise they would not last long). Presumably they were used because they could made locally, out of local materials, so were much cheaper than importing heavy glass or porcelain, and in a dry climate they performed well enough.

    The Arizona beehive itself is not particularly valuable because there are quite a few of them. The other compositions styles are rarer and so worth a little more, but not much, really, because there’s not a whole lot of demand for them.

    The NIA has a page on composition insulators:


  78. Ian Macky Says:

    Looks like the comment system threw away the URL to the NIA composition insulators page. Just search for “nia composition insulators” and it should be #1 result. –ian

  79. jamie Says:

    Hello. Ive just came across what i believe to be a phantom hemingray battery rest. I dont know to awful much about these peices other than there really pretty and i wanna learn more. Would you be able to help me with the value and anything else you might know. From the pictures I’ve found and help from what seems to be a very avid collector its the 7th or eighth one known. Thank you very much.

  80. David Barczak Says:

    Your site was very informative. Thanks for sharing your knowledge with us.

  81. Bob johnson Says:

    I have some 102 pony star insulators, most of the stars are about the same size.
    One has a very small star on it, that’s all the markings on it. Do you have any ideal
    Who made it.
    Thanks Bob

  82. Ian Macky Says:

    Insulators marked with a star were made under contract for General Electric. Any number of glasshouses made GE insulators, including Brookfield, Sterling/Harloe/Novelty (at the Elmer works in NJ), &c. An experienced collector might be able to tell (guess) who made a particular piece based on color, mold style, markings, etc, but I sure can’t.

  83. Bette LoPresti Says:

    I came across your article while doing research on insulators. My brother and I inherited our parents’ insulator collection that includes more than 250 insulators. We are trying to learn more about insulators so we can come up with an idea of the value of the collection. The most unusual one is about an inch and a quarter high and is marked Brookfield Standard on the skirt and Western Electric on the crown. It is my understanding that this was a salesman’s sample and I have read online that these are relatively rare so I was wondering the best way to find the value of it. Thank you in advance for any suggestions for discovering more about this fascinating collection.

  84. Ian Macky Says:

    Brookfield made two different salesman’s samples, in beehive (CD 145) and signal (CD 162) shapes. The beehive is the gem, with very few known; it’s very desirable, and one sold recently for ~$3,000 at auction. The signal, which you have, is more common, though still rare: it sells for about 1/10 the beehive– or maybe more, depending on the color. I have the signal, but not the beehive. –ian

  85. Sue Turner Says:

    Ok so I started collecting over a year ago…..any ideas on how to best display these gems that are everywhere in my home? Build something? If so how with what? Or is there something that can be purchased for this very purpose. They are collecting dust and not properly appreciated as a result of current housing!

  86. Ian Macky Says:

    Sue: most insulators display best with backlighting. So, if you have old-fashioned deep windowsills, they are your #1 choice. I once had a city view I wanted to block for privacy, so I put translucent white plastic over the glass panes, then put shelves in front of the windows, covered in insulators.

    Lit display cabinets are the ultimate, but they are very expensive; I have a space reserved for two of them, but the space is empty. Take a look at photos from insulator shows and you will see almost all of the displays are done in lit cabinets.

    Exceptions: for opal and snowy glass, light from the top-front; for fizzy glass, light from the bottom.

    Outdoors, insulators display well on fences and fenceposts, or put up a short pole and some crossarms and display them original-style. I have a 4×4 post with a bunch of side-pins and ponies.


  87. Juan Delgado Says:

    I have some Hemingray 42 insulators with different mold numbers, different year numbers, and different number of dots. Are they classified as different for cataloging and collecting purpose?

  88. Ian Macky Says:

    Juan, they are all CD 154, however significant embossing variations are distinguished by a 3-digit number following the CD and written in brackets, such as [005] or [100]– but if the only difference is year/mold#/dots, they are considered the same since those difference are not significant. My 2003 McDougald price guide lists 35 variations of the Hemi-42.

  89. Ian Macky Says:

    I thought about this some more and want to add: First, collect whatever you want! It makes no difference what everyone else is doing– though I have heard of people collecting every mold# for a certain embossing, or every shop#, etc, so you wouldn’t be the first if you went that route.

    Second, there are different variation numbers [xxx] assigned depending on whether an insulator HAS date/shop#, etc, but not what those exact numbers are. Year and dots are part of the same date, so they are not broken out.

  90. Bob johnson Says:

    Hi Ian

    I found a 133.4 bullet type insulator with a two part mold line and a crown embossing of just a 0 No other embossing on it. Could you steer me in the right direction to find more information on it .
    Thanks Bob

  91. Ian Macky Says:

    Bob, can’t help you too much. Several companies made the 133.4. The unembossed ones are thought to be by Wormser Glass Company of Pittsburgh– except for the MLOD one, which is unidentified. My old price guide shows the unembossed/MLOD version [020] in lime green and plain green only. Is yous green? They are definitely uncommon, and MLOD insulators are always desirable. You might want to check out this 2001 CJ article “The Bullet”:

  92. Tracy jones Says:

    My mom nust past away and i have 23 glass insulators in many different sizes shapes and colors clear, blue, green, aqua,and even a few purple one they r all from several different manufacturers im trying to identify get there value and most likely sale them

  93. Ian Macky Says:

    I suggest you keep checking insulators.info for an insulator show close to you, then bring your glass to the show, where you will find many people willing to help ID (much easier in person), and perhaps someone to buy the collection. Insulator collectors are generally a friendly bunch and are happy to share their knowledge.

  94. Melissa Says:

    Hello I’m looking for help with the value of a few insulators I have:
    Whitall Tatum Co. No.1 #36 clear
    Brookfield #8 aqua with white specks
    McLaughlin No. 16 dark blue
    Hemingray No.9 Patent May 2, 1893 aqua
    Brookfield #3 dark green

    Thank you for any information you could give me!!

  95. Mike Donegan Says:

    Wow, I just spent about an hour and a half learning about something I had no idea I was interested in. I want to thank you for sharing your interest and enthusiasm for collecting.

  96. Ian Macky Says:

    Mike, I recommend the National Insulator Association (NIA) web site, nia.org, and also Bill Meier’s glass insulator site, insulators.info, the latter especially for its show calender. Maybe there will be an insulator show in your area? Better not go, you may get hooked. Did I mention insulators look great on windowsills?

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