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Insulators were originally made to keep telegraph and telephone wires electrically insulated from wooden telephone poles (especially important in the rain). With the additional needs of rural electrification, there was a big insulator boom in the early 20th century, peaking from the 1920s through the 1940s, with production in the millions per year.

Made from glass or porcelain, in a dazzling array of shapes and colors (e.g. amber, cobalt blue, green, purple), they’re prized for color, beauty, and rarity. Collectors identify insulators by manufacturer (e.g. Hemingray) and by CD numbers, which are based on shape...

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.

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Collection Of Porcelain And Glass Insulators, Rare And Desirable!! Must Sell!!D&e Insulators Olive Black Glass Threadless Rr Telegraph Hat Western Pa Cd737.6Blinding !!yellow Amber!! Cd154 "dominion 42 // D Inside A / 4" InsulatorScreaming Red Amber Canadian Cd154 Dominion 42 Bell Shaped InsulatorAwesome Collection Of Mini And Commemorative InsulatorsMint Aqua Ec&m H Mold Insulator With Amber SwirlIncredible Shooting Comets Unembossed Cd136.4 Heavy Glass InsulatorMajor Milky Swirls Cobalt Blue Cd162 "hemingray // No 19" Signal InsulatorIncredible Separation Aqua/whiskey Amber 2 Tone Cd162 Hemingray 19 InsulatorE.c. & M Co. Sf Glass InsulatorVery Scarce Tiger Striped Dark Yellow Amber Cd102 Sdp "brookfield" InsulatorKiller Lime Green Cd133 "h. G. Co. / Patent / May 2 1893 // Standard" InsulatorDeep Copper Gold H.g. Co. Petticoat InsulatorCd 162 Hemingray No 19 Dark Orange Amber Perfect?Porcelain €Deep Copper Gold H.g. Co. Petticoat Insulator***** " Dazzling" Hemingray No 95 Insulator Cd 185*****Bright Orange Amber Dominion Mint Glass Insulator Cd-154Rare Montreal Telegraph Threadless Glass Insulator From The 1850-1860 Era Cd 742Rare Hemingray Blue Cd185 "hemingray - 95 // Made In U.s.a." Mine InsulatorBeautiful Dark Orange Amber Cd162 H.g. Co. Signal InsulatorFour White Porcelain Insulators With Green Band.Vintage White House Vintage Apple Cider JarsVintage Cd162 Mclaughlin 19 Glass Insulator*has A Nail Inside The Glass! AmazingRare Porcelain Insulator With Iron ShellA.m Tel. & Tel. Co.  Glass Insulators Green Slag Look!!!Great Looking Old Green W.brookfield Cable Insulator New York 1870Beautiful Opalescent Hemingray 128 InsulatorGlowing Depression Glass Green Backwards 2 Cd154 "mclaughlin // No 42" InsulatorTransformer Bushing Insulator - AmberMulford & Biddle U.p.r.r. Aqua Threadless Insulator3 ½”plain Round Red Lightning Rod Ball Insulator Glowing Lime Green Cd145 "h. G. Co. // Petticoat" Beehive InsulatorDead Mint Emerald Gren Cd154 "mclaughlin - 42" InsulatorMint Emerald Green Spiral Groove Cd147 "patented // Oct 8th 1907" InsulatorVery Tough Much Skirt & Crown Embossed Light Aqua Cd133 Brookfield InsulatorClassic Amber Eared Mickey Mouse Glass InsulatorScarce Light Aqua Cd162 "o.v.g. Co. // Petticoat" Signal InsulatorVivid Royal Purple Cd145 "g.n.w. Tel. Co." Canadian Beehive InsulatorReally Tough Dark Purple Cd162 W.f.g. Co. Signal InsulatorDark Aqua Cd205 Snowman Shaped Brookfield Transposition InsulatorIce Aqua Bubbled Cd252 "no 2 Cable" Mouse Eared InsulatorThree Heads Green Glass InsulatorElectric Blue H G Co. Glass Insulator Petticoat May 2 1893Rim Embossed Chicago Diamond Groove InsulatorBeautiful Amber Bushing InsulatorLot Of Vintage Antique Ceramic Wire Insulators Electrical Or Antenna Birnbach Cd 143 Double Threaded InsulatorSeven "whitall Tatum Co. No. 1" Aqua Blue/green Antique Glass InsulatorsQuite Tough Green Star Embossed Cd162.3 Fat Signal InsulatorBlue Cd 257 Mickey Mouse (early Wide Groove Hemingray) Double Pat DateCd 121 W.g.m. Co. Glass Insulator Peachy StrawBeautiful Deep Olive Green Cd 113 Hemingray 12 InsulatorCd 131.4 Patent Dec 19 1871 Glass InsulatorExcellent Crisp Aqua Base Embossed Cd135 Chicago Insulating Co InsulatorVintage Antique Marbleized Patterned Ceramic, Glass Or Porcelain Insulator?Radio Strain Spiral Dog Bone Glass Insulators 3 Pcs.Fred M Locke Victor Ny (oversized)Amber Olive Green Hemingray 19 Glass InsulatorCd 196 H.g.co. Sdp Transposition Insulator
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