Hemingray Glass Company

Hemingray Glass CompanyHemingray Glass Company

Cincinnati, Ohio (1848-1852)
Covington, Kentucky (1852-c.1890)
Muncie, Indiana (1888-1933)
Muncie, Indiana (1933-1972) [Owens Illinois Glass Co.]

Hemingray is the best known and was the most prolific glass insulator manufacturer in the world. Although best known for their electrical insulators, Hemingray also produced many other glass items, including bottles, fruit jars, pressed glass dishes, tumblers, battery jars, fishbowls, lantern globes, oil lamps, and much, much more. Hemingray operated under several slightly different company names during it’s long history, first as Gray & Hemingray (1848-1856), then Gray, Hemingray & Bros. (1857-1860), Gray, Hemingray & Brother (1861-1863), Hemingray Bros. & Company (1864-1867), R. Hemingray & Company (1868-1869), and finally incorporating as the Hemingray Glass Company, Inc. in 1870.

Hemingray began as a small operation in Cincinnati in 1848. In 1852 the actual glasshouse operation was moved across the Ohio River to Covington, Kentucky, but the business office/showroom remained in Cincinnati until 1881, when it too was removed to a new building in Covington.

With the explosion of manufacturing concerns during the 1880s in the “natural gas belt” of central Indiana & northwestern Ohio, a new glass manufacturing facility was built in Muncie, Indiana and production commenced there in 1888.  The exact year when actual insulator production ended at the Covington site is still undetermined, but it was likely sometime in the 1890-1894 period.  The Covington factory also re-opened for a short time in the 1900-1902 period. The business offices remained at Covington until 1919, at which time all operation was moved to Muncie.

In 1933 the Muncie factory officially became the “Hemingray Division”, a subsidiary of the Owens Illinois Glass Company (factory #26),  but insulators made after that year continued to carry the “HEMINGRAY” name.  Date codes were embossed on most insulators made after 1934, and the majority (but certainly not all) of post-1934 production was made in clear (colorless) or off-clear glass.

Hemingray “Mickey Mouse” style cable insulator

 

 

 

Glass building blocks, a major item made for many years, was discontinued in March of 1966 and production of insulators was discontinued in 1967….. although the factory continued to produce television face-plates until closing permanently in 1972. (The very last glass insulators made were produced at the Indiana Glass Company factory located in Dunkirk, Indiana, using molds that had been moved from Muncie to that location).

Embossings on Hemingray-produced electrical insulators include “PATENT MAY 2 1893”, “PAT DEC 19 1871”, “H.G.CO.”, “HEMINGRAY”, “LOWEX” , “KIMBLE”, and others. The earliest insulators made by Hemingray have not been specifically identified but would almost certainly be circa 1850s threadless or possibly “Wade” types.  Lightning rod insulators, and various sizes of spool insulators were also made.

Two Hemingray-42 glass insulators, in "Hemingray Blue" and a medium shade of true green.

Two Hemingray-42 insulators – in “Hemingray Blue” and a medium shade of true green.

The HEMINGRAY-42

In 1921, the “Hemingray-42” style insulator was introduced which was an update/replacement for the Hemingray NO. 40 insulator. (The No. 40 had been in heavy production since 1911, for telegraph lines). The “new and improved” #42 model very quickly gained in popularity for standard open-wire communication lines, and was soon the most popular and common insulator made for both telegraph and telephone lines.  Many railroad lines used them for their telegraph communications, and the style became the standard for A T & T long distance “toll” lines.  The 42 is classed as a “CD 154”, in the “consolidated design” cataloguing/identification system used by insulator collectors. Each CD number is assigned to a basic shape (profile/size), regardless of the exact embossed lettering, glass color or base type.

The HEMINGRAY-42 is almost certainly the most common glass insulator ever manufactured and used in the United States. (The Hemingray No. 9 is considered by some to be the most common insulator, but I think the 42 has a slight edge). The Hemingray No. 9 style was produced from about 1892 to 1955 (63 years) and tremendous numbers were used across the country on local telephone line systems. Alot of the earlier 9s had already been dismantled, destroyed or discarded (from line upgrades as well as ice storms, windstorms, fires, BB gun vandalism, etc) long before the insulator-collecting hobby started to become popular in the mid-1960s, so it is harder to make a direct comparison on total numbers ever made, since so many 9s were already in dumps and landfills  before the wholesale dismantling of the railroad telegraph lines was fully underway during the 1970s-1990s.  So, today the 42s are much more commonly found in such places as antique malls and flea markets.

The earliest Hemingray-42s have sharp drip points, which are believed to have been phased out approximately 1923 or 1924.  The RDP (round drip point) version probably came into production sometime in 1924, although admittedly that is just an “educated guess”. Tremendous numbers of Hemingray-42 insulators with RDP bases were made, for the most part in aqua or “Hemingray Blue” (a richer blue-aqua made by Hemingray, as well as Ball Brothers, maker of the “Ball” fruit jars) during the 1924-1930 period.

The transition to off-clear glass began approximately 1930.  By 1933 virtually all Hemingray-42s were being made in off-clear, very pale “ice blue”, or clear glass.    Date codes were began to be implemented around 1933 or shortly afterward, that being the year that Owens-Illinois acquired ownership of the Hemingray facility.  Judging from date codes, “Ice blue” (an off-clear with a faint bluish-gray tint) seems to have been made a lot during the year 1935. The majority of clear and off-clear glass Hemingray-42s (from the years 1934 to 1961) carry mold/date codes.  Typically, the first number (before the dash) represents the mold number, the second number (s), after the dash, indicates the year the mold itself was made.  Any dots (if present) after the second number is added to find the year the insulator itself was molded.  For example, 12-41::: [six dots] would indicate an insulator made in 1947 from mold # 12.   However, not all 42s have this type of date code, especially some of the earlier units dating between 1930-1940. For more information, please see a query I received which is posted near the bottom of this page.

The 42 continued in production until at least 1961, as that is the latest date code seen (so far). If you know of a 42 which was made later than 1961, please contact me with the exact date code information.  As stated earlier,  the Hemingray-42 is probably the most common U.S.-made glass electrical insulator in the world.    The great majority are found in aqua, Hemingray Blue or clear glass.   Less common are examples in shades of true green (i.e. showing no blue influence in the color) or in two-tone (half aqua, half green).  A few examples are known in carnival glass, white milkglass and opalescent (cloudy off-white).   It is likely that at least one Hemingray-42 can be found in nearly every large antique mall in the country.  Even accounting for their commonness, nevertheless these are authentic relics of a bygone era in America, and will soon be true antiques. (Officially, an antique is an object at least 100 years old……..that status will be reached in 2021) .

 

CD 132 Telegraph Insulator, made by Hemingray, marked “PATENT / DEC 19 1871”.

 

Hemingray is well-known among antique fruit jar collectors for several types of jars they manufactured in the mid-late 1800s and up into the early 1900s. The most famous of those would be the “GLOBE” brand fruit jar which is found in a range of colors, including, of course, many shades of aquamarine, as well as several shades of amber including honey amber, yellow amber, orange amber;  also olive green, blackglass, clear and cornflower blue.

Tremendous numbers of insulators embossed with the lettering “PATENT / MAY 2 1893” were made from 1893 through at least 1910, (i.e. the period of 17 years during which the patent for Hemingray’s “drip points” along the base of the insulator was in effect), and probably even for several years afterward on a few insulator styles.
For more info on Hemingray and Hemingray products, check out these sites:
Hemingray.com ;   Hemingray.net ;   Hemingray.info.

NOTE: for a basic list of glass factories in the United States that are believed to have made glass insulators at some time in their history, go to my “Glass Insulator Manufacturers” page here.

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To go to my site HOMEPAGE, please click here.

(Pictured at the top of the page: CD 122 Hemingray-16 “long distance”or “toll” telephone insulator in bright “Seven-up” green.

[Info sources for this page: Bob Stahr; David Dale; Clarice Gordon; Glenn Drummond; Alice Creswick (The Fruit Jar Works); articles in Crown Jewels of the Wire magazine].

37 Responses to Hemingray Glass Company

  1. T. J. Handal says:

    Hi! I have a 1 oz glass with a glassmark on the bottom of an H in a circle. I have heard that this is a Hemingray mark from between the 1920-1940s, but I can’t find much info on anything except insulators. Anywhere that would have such information? Thank you for gathering such a vast amount of information for us glass history buffs!

    • David says:

      T. J.,
      I have doubts that the glass was made by Hemingray. You might try contacting Bob Stahr, webmaster of Hemingray.com, for his opinion.
      ~David

  2. Desiree says:

    Hello. I have a green Hemingray insulator that is marked with the name and a -19 on one side and Made in the U.S.A. on the otherside. Can you give me an estimated date of production and what this one was made for? And, how do I find the value and where can I sell to collectors?
    Thanks,
    Desiree McKinney

    • David says:

      Hi Desiree,
      Hemingray-marked insulators with the phrase “MADE IN U.S.A” are believed to date after 1919. I am assuming your insulator is a blueish-green (aqua) color, not a “true green” with no hint of blue in it. Most aqua insulators made by Hemingray date up to the circa 1930-1932 period, as they began switching over to clear glass during the early 1930s. So c. 1919-1931 would be the time span I would suggest for your insulator.
      The Hemingray-19 is a type of “signal” insulator, often used for relatively low-voltage electric lines, railroad signal lines and fire alarm circuits. They were sometimes used on ordinary telegraph and telephone lines. I try not to give advice on values, other than to suggest you search ebay over a period of time and see what actual examples of any particular insulator sell for (actual “Completed Auctions”, not minimum bids or “buy it now” prices which are often greatly over-priced!) . Most of the Hemingray-19s were made in aqua and they are very common. However, other, more unusual colors are also found, and they are much higher in value.
      Best regards,
      David

  3. Kevin says:

    Hi David,
    I have what I believe to be a Hemmingray CD145 Beehive double petticoat with the following embossing: H.G.CO with the word PETTICOAT on the opposite side of the skirt. It has a B embossed on the top of the dome. This insulator is light green. Would you be able to give an approximation as to when this may have been made. I am a fairly new collector and this is quite different from the other Hemmingrays that I have.

    • David says:

      Hello Kevin,
      You have the earliest style of beehive telegraph insulator made by Hemingray. They were made from APPROXIMATELY 1886 to 1895, (no one knows for sure, but that is probably about the best guesstimate Hemingray researchers/collectors can give), at both the Covington, KY and Muncie, Indiana factory locations. They are most commonly found in medium aqua shades and many slightly different shades of light green, but many other colors have been found including sapphire blue, light pastel blue, orange amber, yellow amber, true medium and dark shades of green, clear, off-clear, purple, and white milkglass (one example known of that color!).
      They usually bear a “shop letter” above or below the embossing on the front or rear, and/or with a letter on the dome. Some bear no shop letters at all. The shop letters known are A, B, C, D, E, “upside down L” (F without a crossbar), G, H, I, J, K, L , M, and backward N. There appear to have been at least 3 or 4 slightly different molds manufactured for every letter except the upside down L. They are very popular with collectors because of the wide color range and the shop letters.
      It is assumed that around 1895 (give or take a year or so) the very slightly narrower “H.G.CO.” beehive type WITHOUT the “PETTICOAT” lettering (and usually with an “H” on the top of the dome) was phased in… which soon became the most popular telegraph line insulator made at Hemingray for a number of years……probably to about 1911 when the Hemingray No. 40 was introduced.
      Hope this will be of some help!
      David

  4. Christopher says:

    Hello David… Real quick.. I live and grew up on the NYC man “airline” and a lot of the insulators are soooo varietied. The one I first ask of is my Hemingray-42 but the number 2 is flipped over.. never seen one like that before.!!??? 2nd.. what are those 4 clear insulator owens Illinois cluster sets time frames? I seen 2 or3 of these aluminum frames with the skinny insulators and each one of the 4 has the symbol and a #58. Lastly. We live near the old Toledo and western trolley line near Pioneer and Fayette., the green insulator skirt is almost double diameter than an average hemingray and the word OHIO is molded in it, however it’s missing the other 1/2.

    • David says:

      Hi Christopher,
      You have found an example of a mold-maker error…. the Hemingray-42 with the “backward 2” is much harder to find, and is worth a premium over the normal ones.
      The large insulator with the word “OHIO” embossed on it is a CD 302. Search google with more info on the “CD 302” power line style insulator made by Hemingray. There are several slightly different variants of that type, one is marked “MUNCIE TYPE” or “MUNCIE”, others are marked “OHIO” along with the standard “PAT MAY 2 1893” embossing which refers to the patent issued to Hemingray for their “drip points”.
      I am guessing you are talking about a small clear “spool” insulator made by Owens-Illinois, it is classed as a “CD 1049” and was made in the 1950s or possibly into the early 1960s. I am guessing yours has a date code for 1958. If there are any dots after the “58” add them to get the actual year the insulator was made. I am not sure of how late they were made, but they are definitely one of the more recent, modern types of glass insulators made at the Hemingray factory in Muncie, Indiana.

      Best regards, David

  5. Dave Strothmann says:

    My father-in-law passed away recently and he was a collector of glass and ceramic insulators. Probably had close to 100 of them in excellent condition with many styles and colors including glass and porcelain insulators. I’d like to find a source of information that can help us understand the value of his collection. I really appreciate your site with all this information. Any tips you can provide on determining their value would be greatly appreciated.

    • David says:

      Dave, the majority of insulators found do not have a high value (most ranging in the 50 cents to 5 dollar value range). But there are also quite a few that are much scarcer and have values that range into the hundreds or sometimes even thousands of dollars. My site is not intended as an appraisal site. Your question is very difficult to answer in a brief way since the field of collecting glass and porcelain insulators is very wide.
      There are many websites that give information on various types of insulators. Here is a basic page with some of the most commonly asked questions on insulators….
      http://www.insulators.info/general/faq.htm

      Another page with general info……
      http://www.ebay.com/gds/World-Wide-Insulator-Collecting-and-ID-Guide-/10000000000020064/g.html
      There are insulator price guides available (hard copy and digital versions) but they are not free.

      Here’s a good site and this particular page has lots of basic questions on Hemingray insulators:
      http://hemingray.info/database/faq.html
      I hope this will be of help,
      David

  6. Debbie says:

    I have a clear mason”a perfect nov 30th 1858 jar with H47 on the bottom of it, can you tell me if it was manufactured by hemingray company?

  7. Bob says:

    I’m doing a school project, and I need to know what a glass insulator does (or did). My group would appreciate answers!

    • David says:

      Hello Bob,
      I don’t profess to be an electrician, scientist, or engineer; I’m just a glass collector (and interested in the history and use of glass). But, to answer your question as simply as possible, insulators were used to “insulate” electrical lines including lower-voltage communication lines (telephone or telegraph), up to and including higher-voltage lines that carry electrical power. The word “Insulate” in this instance basically just means to help prevent, or greatly reduce electrical current loss over distances. If there were no insulators, the electric current passing through the metal wire would “leak” away at every point where the wire was touching a post or pole, especially during damp weather. Soon the current would be reduced to practically nothing, and it would be impossible or difficult to carry the electrical current very far. The material GLASS itself is an insulator, it resists the passage of electicity. That is, electic current does not easily go THROUGH glass. Nowadays, lots of insulators are still in use on utility lines, but MOST of them are now made of porcelain (some people would call them “pottery” or ceramic) or high-grade plastic formulas. Just for curiosity’s sake, try looking around your neighborhood and see if you can spot insulators overhead on electrical power lines. They are usually gray, white or brown in color. Some are smaller “pin types” and others may be larger “post insulators”.

      Glass insulators are now almost obsolete in the United States, although some of them are still in service here and there around the country. And some countries around the world use larger styles of glass insulators for high-voltage power lines even now.

      Please check out my webpage on Glass Insulators (in general), plus there are gobs of webpages online where insulators, both glass and porcelain, are discussed in more detail.

      I hope this will help on your project! Take care,
      David

  8. Bob Johnson says:

    Hi
    I have a HemingRay 42 with the back Made in the USA. On the dome is 1. Do you know why. Thanks

    • David says:

      Bob, no one is 100% sure what the dome number ‘1″ signifies which is seen on THE TOP of some of the HEMINGRAY-42s. It might have been meant to signify a particular set of molds used on a particular automatic insulator-pressing machine. Again, the purpose (in the case of THESE PARTICULAR INSULATORS!!!) is not certain at this time.
      David

  9. April Reese says:

    I have the aqua blue HEMINGRAT – 42 and on the other side made in the U.S.A but there is no other numbers on it. What does that mean and when would it have been made? It is the large insulators.

    • David says:

      Hello April,
      I assume your writing “T” instead of “Y” in “Hemingray” is a typo. “42” is the “model number” of that style insulator. The aqua and “Hemingray Blue” (stronger bluish aqua, some people call it “turquoise”) insulators marked “HEMINGRAY – 42” on one side and “MADE IN U.S.A.” on the other side are the most common variants of this style of insulator. They were made in very large quantities and those colors generally date from 1921 to around 1930. It is impossible to assign an EXACT year of manufacture to any of the aqua or Hemingray blue specimens. (No one is absolutely positive when the last aqua 42s were made, but probably circa 1930-1931). In later years, when mostly clear or off-clear glass was used, mold numbers and/or date codes will be seen on most examples. I hope this helps answer your question.
      ~David

  10. jerry says:

    Hello
    I have several of these Hemingray insulators. Some have the name with a 9 and they are stamped 31-52 with a colon. Does the 9 signify 1939? Thanks

    • David says:

      Hi Jerry,
      No, the “9” is a model number (style number) assigned to that particular type of insulator made by Hemingray Glass Company and does not indicate the year it was made. The number 9’s are “pony insulators”, smaller types used primarily (but not always) on local, short distance, low voltage telephone lines. On older insulators, the wording is typically “HEMINGRAY / NO. 9”, on more recent examples (usually in clear glass) the phrasing is usually “HEMINGRAY-9”. The numbers on the other side of the insulator (such as 31-52, as in your case) is a combination mold and date code. (Please see the comments farther down on this page where I have discussed this in more detail in several posts). Basically, the “31” is a mold number, identifying the exact mold the insulator was produced in, and the “52” is a date code indicating what year the MOLD ITSELF was made (1952). If there are any dots to the right of the date code, add one year for each dot to arrive at the year the insulator was made. In your case since there are just 2 dots, that particular insulator was made in 1954.
      ~David

  11. J says:

    I just found a 42 with 0_4: on it. Im pretty sure I have that figured out but I can’t seem to find any information on what the 52 under “made in America” is. Does any one happen to know what that means?

    • David says:

      Hi J, The “52” underneath the “MADE IN U.S.A.” is a mold number. These insulators were made in such tremendous quantities that many different “Hemingray-42” molds were being used simultaneously to produce them. Each mold (in this instance) was engraved with a mold number as identification, so if there were any problems with the finished product, the mold involved could be quickly identified just by checking the mold number on the insulator. (Over the years, there was some variation in the presence/absence of a mold number, and/or where it was placed on the insulator). Hope this helps,
      David

  12. Greg says:

    I have acquired one that as an 8 as well.under Hemminggray – 42. It is a little different in that it says 0-8 and then 5 dots. On the opposite side it says 18 under made in USA. Others have said they just had the 8 or 4 without the 0. Do you have any idea what the 0 before the 8 might mean?

    • David says:

      Hi Greg,
      OK, first of all, I want to make CLEAR that no one is ABSOLUTELY certain what the early date codes signify, but from information put out by N. R. Woodward and other researchers, it seems the chances are very high that the “O” was engraved on many insulator molds, such as the Hemingray-42’s, around the time that Owens-Illinois Glass Company took over the Hemingray factory (which occurred in 1933). Some of these Hemingray-42s, usually in an off-clear glass, are marked with just a “O” immediately below the “HEMINGRAY- 42” marking. Others have additional markings such as O-4 or O-8 (with or without dots). The “O” is believed to be an initial for “Owens-Illinois” and the “4” is believed to stand for “1934”. This would make sense since 1934 is the year after Owens-Illinois took over. If an insulator has an “8” it is believed to have been made in 1938. (Of course, add any dots that might be present to the right of the 4, or the 8, to find the actual year an insulator was made). Your insulator was made in 1943. (8 + 5 dots). This system of date codes started changing gradually (on some insulators) around 1938, such as on the CD 155s (Hemingray-45).
      Basically, this would be the proposed interpretation for Hemingray-42s of this era (in clear or off-clear glass):
      O 1933
      O-4 1934
      O-4. 1935
      O-4: 1936
      O-4:. 1937
      O-8 1938
      O-8. 1939
      O-8: 1940
      O-8:. 1941
      O-8:: 1942

      Hope this helps, David

  13. Laura says:

    Hello, I have several Hemingray insulators that have 9, 12 or 16 on them, all in the aqua color. Three have the sharp drip points and one has rounded drips. Can you give me an idea where I could find information on these? Thank you!

  14. Chuck McBride says:

    Hi David,
    I have a Hemingray Insulator, it is a pale light green that reads HEMINGRAY 20-41. I totally understand from your instructions above that is mold number 20 made in 1941 and the insulator manufactured in 1942. On the opposite side it reads C,S.A. any thoughts as to what that stands for? Also on the inside where the threads are it is lead what if any is the reasoning behind the lead. And thanks for such an informative site!

    • David says:

      Hi Chuck,
      From your information, the Hemingray style insulator you have sounds like the “CD 128” in the “CD number” classification system used by collectors. You can google that and see various examples of that style of insulator. Besides the Hemingray versions, the CD 128 was also made in LARGE quantities by Corning Glass Works, and their version is marked with the PYREX brand name. Whitall Tatum also made some of them, as well as Kerr, marked with “C S C”.

      The insulator type you have is found with one of three different “CS” markings, including either C.S.A., C.S.O., or C.S.C. Basically, the “C S” stands for “Circuit Carrier: Steel pin” but no one is sure what the third letter indicates. (Occasionally, a myth has circulated that the CSA stands for “Confederated States of America” which implied those insulators were Civil War era. Obviously, not so!)

      The “brass bushing” or “thimble” insert (it looks like lead but I think they are actually made of brass) was put in place by machine, at the time the insulator was made and the glass was still very hot. It was included to make sure the threads were perfectly standard and no slight changes in the dimensions occurred during extremely hot or cold weather, and (I assume) as an additional strengthening/buffering agent since the insulator would be installed directly on a steel pin.

      Here is a link to Christian Willis’ Hemingray.info site, where he discusses the CD 128: http://www.hemingray.info/database/detail.php?cd=128.

      Also, check out this page from a 1935 article: http://reference.insulators.info/publications/view/?id=4460
      Scroll down to the paragraph entitled “Insulators to 27 Foreign Countries” where there is a brief mention of the process of automatic production of that type of insulator and addition of the metal thimble.

      I hope this helps, and thanks for your query!
      David

  15. Deb says:

    Hi David,
    I just acquired a No. 42 (bluish green) with no date. Can you help me to date it or determine its history?

    Thanks!

    • David says:

      Hello Deb,
      Unfortunately, there is no way to date the aqua-colored Hemi-42s. As you probably realize (but I will repeat it here for other readers), the “42” is a model (style) number and gives no info at all concerning date of production.

      All that can be said is that the aqua (turquoise or blue-green, as well as Hemingray Blue, and some are found in true green) 42s date from 1921 to around 1930 or 1931. If it has sharp drip points, it probably dates from somewhere in the 1921 to 1924 time period. If it has round drip points, it probably dates sometime between 1924 and 1930. Those dates are not “written in stone” but are as close to accurate as collectors can be at this time. None of the aqua 42s have any type of production date codes on them. After around 1933, the 42s were mostly being made in clear or off-clear glass, and by that time, date codes were coming into use.
      Best regards,
      David

  16. Nicole says:

    Hi David,
    I just acquired an insulator and am trying to date it. Similar to Jim above, I think it’s an early code variation. Under Hemingray – 42 it says 8 with 7 dots. I am unclear as to what would be the mold number vs. the date? On the other side is 10B under Made in the USA. If you could clarify, I’d appreciate it. Thank you!
    Nicole

    • David says:

      Hi Nicole!
      Yes, that’s another one of the earlier Hemingray-42’s with a different type of code. In these cases, the “8” is believed to stand for 1938. Most Hemingray-42s with this style of code configuration will have *either* a “4” or an “8” (standing for 1934 and 1938, respectively, years when new sets of molds were introduced during that time frame) as part of the date code. The 4 or 8 may (or may not) be followed by dots. In your case the insulator mold was produced in 1938, and the insulator itself was molded in 1945 (1938 plus 7 dots). For each additional year that these molds were used, another tiny “hole” was drilled into the inside surface of the iron mold, which appears as a raised ‘dot’ on the surface of the finished glass insulator.

      I have a No.42 from that same mold set. In the case of the example in front of me, the “8” is followed by 7 dots, (same as yours) BUT the only difference being a different mold number/letter combo. The 10B is a mold number, serving to identify the exact iron mold used. On the example I have, the mold number is 6A. On these particular insulators the mold number (or mold number/letter) is indeed on the REVERSE side, positioned underneath the “MADE IN U.S.A.” embossing.
      There is a range of number/letter combos known, including the letters A, B, C, and D (perhaps higher letters on some insulator styles(??) . I am not 100% positive, but I have heard (or read) that those letters were simply a means of “shorthand” when numbering molds, that is, instead of numbering molds past 99, they started over again at “1” and added a letter. For instance, “10B” would mean “mold #110” or “6A” would mean “mold #106” within a particular mold series.
      The number of different molds used to manufacture these insulators is staggering……..hundreds and hundreds of molds, and many millions of insulators made!
      Hope this helps,
      David

  17. jim davis says:

    we have a few hemingray and one mclauchin inulators. one # 42 hemingray
    clear has #16 8 :: it doesn’t seem to be as easy to determine date made as suggested.

    • David says:

      Hello Jim,
      Well, this is one of the early date code variations that doesn’t conform to the more typical configuration used later on. In this case, the “8” signifies 1938.
      After Owens-Illinois took over production of the Hemingray plant in 1933, they started a date code system and many of the earlier Hemingray insulators of that time period will have (to the right of a mold number) either a “4” (meaning the mold itself was produced in 1934) or an “8” (mold made in 1938) often followed with dots. In your case, this can be read as “insulator produced from mold #16 in the year 1942”. (8 plus 4 dots equals 1942). I hope this makes sense. Thanks for writing!
      David

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      Hello, please allow me to point out that Hemingray-made insulators (in fact, nearly all glass insulators, no matter the age or maker) are examples of PRESSED GLASS, not BLOWN GLASS. The insulators were made by forcing molten glass into hollow iron molds by pressing, either by hand or machine methods. This is a different type of process from the BLOWING of glass, (by mouth or by machinery) as is done to produce hollow articles such as bottles and jars. Yes, most insulators, say, before 1900, tend to be crudely made, but that characteristic in itself does not indicate they were blown. Both blown and pressed glass, when referring to “industrial” or “utilitarian” glass objects, are typically made of glass that can be described as “crude” because less care was taken in their manufacture. On another note, “Fancy” tableware for household use is somewhat of a different ball game, and the glass production for those types of articles was usually held to somewhat more stringent quality control standards. As far as your mention of large quantities of “slag glass” from iron furnace operations being used for making new glass, not sure where you got that info……..please give sources. I’ve not heard of that as far as making insulators or bottles. Thanks for the link… David

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