Pyrex Glass (Corning Glass Works)

                                 PYREX GLASS

Corning Glass Company/Corning Glass Works, Corning, New York (1875-to present), now known as Corning Incorporated 

The trademark “Pyrex” was introduced in 1915 for Corning Glass Works’ borosilicate  heat-resistant glassware formula.  This glass had been developed in 1908 under the name “NONEX” and used, at first, mostly for railroad lantern globes and electrical battery jars.

Bessie Littleton, the wife of Corning engineer Jessie Littleton, asked her husband to bring home some samples of that type of glass for her to try baking with, and when baking a cake she found that the new borosilicate glass stood up to heating in an oven without breaking.  This led to the creation of the “PYREX” brand name.

The brand name “PYREX” is a contraction of  “Pie” and “Nonex”.     This stronger, more durable glass was first used with pie plates and kitchen-related glass subjected to high temperatures.

VERY large quantities of kitchenware, ovenware, cookware, measuring cups and pitchers, as well as technical, scientific and laboratory glassware have been made for well over a century.  Also, large quantities of industrial glass such as  glass electrical insulators for telephone and power lines were made over many years.

Pyrex glass cookware has been a staple in American households for many decades. Some of the most popular items include square and rectangular baking dishes/pans (for cakes, casseroles,  home made bread, baked puddings, etc) of various sizes and designs.  Also very popular have been other items such as oval and round casserole dishes, refrigerator dishes, mixing bowls, butter dishes, pie plates, serving bowls, measuring cups, teapots, rolling pins, custard cups,  nursing bottles, reamers, roasters, carafes, coffee makers and other items.


Three PYREX brand heat-resistant semi-translucent milk glass mixing bowls made by Corning Glass Works. All are marked with the style number "402" on the base.
Three PYREX heat-resistant mixing bowls made by Corning Glass Works. All are marked with the style number “402” on the base.

Pictured here are examples of vintage PYREX name brand ovenware casserole / mixing bowls. The style or inventory number assigned to this size/type of bowl appears to be “402” as each example has that number embossed on the base, as well as the lettering “TRADE MARK / PYREX / R [in circle] / MADE IN U.S.A. / OVEN WARE”.

Each measures about 7 & 1/4th inches in diameter and 3 & 3/4ths inches in height.  They are made of white translucent milk glass with colored “flashing” on the outside surface. They probably date from the 1960s – 1980s.

PYREX: Base markings on red and white PYREX glass mixing bowl. This bowl was made by Corning Glass Works and probably dates from the 1970s or 1980s.
Base markings on red/white “402” style PYREX mixing bowl (shown on lower right in photo above).

Lime green PYREX glass baking / casserole dish made by Corning Glass, dates from about 1957 or early 1958. The style of pan was introduced in about 1952.
“Lime Green” #231 PYREX glass multi-purpose casserole / utility / baking dish, 1 & 1/2 quart size.   This color/style was introduced in 1952 according to author Barbara Mauzy.  This particular example was a wedding present for my mother in early 1958 so I can date it as having been made in about 1957 or very early 1958. The color looks almost like a “Mint” green under some lighting conditions.

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Bottles and other types of heat and chemical-resistant laboratory glassware are also found with the “PYREX” name embossed on the bottom.    Glass tubing, test tubes, lab chemical bottles, funnels, beakers, serum vials and other miscellaneous laboratory equipment and containers were made in large quantities.


Small serum/vaccine type bottle marked "PYREX" on base. This measures only 2.25 inches tall.
Small serum/vaccine type bottle marked “PYREX” on base. This measures only 2.25 inches tall.
Base of tiny serum bottle (shown above) marked "PYREX" , made by Corning Glass Works.
Base of tiny serum bottle (shown above) marked “PYREX” , made by Corning Glass Works.

Typical Clear borosilicate glass PYREX chemical / laboratory bottle. This one measures 8 inches in height. These bottles were manufactured by Corning Glass Works.
Typical clear borosilicate glass PYREX chemical / laboratory bottle. This one measures about 8 inches in height.

Just a fun note —   some of the glassware you might see in a “mad scientist” laboratory scene in old movies are very likely products of Corning!


Two small vintage collectible items marked "PYREX":   Glass Percolator top and small electrical plug-style fuse. The percolator top is embossed "PYREX  MADE IN U.S.A." and the fuse is marked in raised lettering on the base "PYREX   G.E.CO.  U.S.A.".
Two vintage items marked “PYREX”:   Glass Percolator top and small electrical plug-style fuse. The percolator top is embossed “PYREX  MADE IN U.S.A.” and the fuse is marked in raised lettering on the base “PYREX   G.E.CO.  U.S.A.”.

CD 233 style power line insulator, circa 1930s or 1940s.  Marked "PYREX REG. U.S.PAT.OFF. // 661 / CORNING  MADE IN U.S.A."
CD 233 style power line insulator, circa 1930s or 1940s.  Marked “PYREX REG. U.S.PAT.OFF. // 661 / CORNING  MADE IN U.S.A.”

Two colorless PYREX glass insulators. These are classed as "CD 128" by electrical insulator collectors.
Two colorless PYREX glass insulators. These are classed under the  “CD 128” style by electrical insulator collectors.

Pyrex Glass Insulators

Huge numbers of glass electrical insulators were made by Corning with the “PYREX” brand name embossed on them.   The great majority of them are found in clear glass.  Some insulators were made in  “Carnival Glass” (glass made with an iridized surface coating of mineral salts) , bearing the PYREX / CORNING brand marking.

The most common Pyrex glass insulator (found in clear) would probably be the CD 128 style (shown in photo above).  A search of the internet, such as Google Images pages with  “Pyrex glass insulator”  and “CD 128” would bring up more examples of that particular shape. There are more than 25 different styles of PYREX  pin-type insulators known, plus others such as radio strain types.

According to information in this web article by collector and researcher Greg Hafer, all Pyrex insulators were made between 1923 and 1945.
PYREX INSULATORS – Greg Hafer Article


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NOTE: In 1998, Corning discontinued the production of their PYREX line of glassware, (concentrating instead on their lines of industrial and tech-related products) and the rights to the PYREX brand name were assigned to World Kitchen, LLC (under that name 2000 to 2018,  later known as Corelle Brands, now [2023] known as Instant Brands).  Their website is located at:   https://www.corelle.com/about-us .   More information on current products can be found at that site. (UPDATE:  Instant Brands has apparently filed for bankruptcy as of June of 2023).


The  original formula for the glass produced for the United States market was evidently changed, after 1998, to a  tempered soda-lime glass.   There have been complaints by consumers that this recently-made glassware (ovenware, etc) has sometimes shattered, and appears to be inferior to previous standards of durability characteristic of the earlier borosilicate formula.

For a well-written and researched article with details on their change from borosilicate glass to a soda-lime glass formula in recent decades, see this page:
The PYREX Glass Controversy That Just Won’t die


Some basic information (with questions and answers concerning Pyrex glassware) can be found on this webpage which is part of the Corning Museum of Glass website:  https://pyrex.cmog.org/faq


Collecting Vintage Pyrex (From the “Adirondack girl at heart” website):

https://adirondackgirlatheart.com/collecting-vintage-pyrex/


Brief History of Pyrex:

https://www.foodandwine.com/lifestyle/kitchen/history-of-pyrex


Corning Museum of Glass article: “A Century of Pyrex”:

https://www.cmog.org/article/pyrex

 


A Brief History of Pyrex Kitchenware

https://www.pyrexcollector.com/history.php


Marta Stewart’s site article about collecting vintage Pyrex:

https://www.marthastewart.com/7692706/collecting-vintage-pyrex


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Here is a keyword search of current Pyrex glass items for sale on the ebay auction site:

PYREX glass items on Ebay


“PYREX” MARKED INSULATORS ON EBAY

PYREX glass insulators on Ebay


For more detailed background info on this glass, check out the Wikipedia entry about Pyrex Glass:  PYREX insulators – Wikipedia


For an extensive alphabetical list of glass manufacturers’ marks seen on bottles, fruit jars, insulators, tableware and other glassware,  please click here to go to the Glass Bottle Marks pages

Please click here to go to my “Glass Bottle Marks” website  Home Page.


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12 thoughts on “Pyrex Glass (Corning Glass Works)”

  1. As an amateur astronomer, I would mention that tons of Pyrex glass has been made into reflecting telescope mirrors over the years. I have 10″, a 15″, and 20″ mirrors in Dobsonian
    telescopes. Most are 2″ thick and weigh up to 60 lbs. They make good telescope mirrors because of their low expansion and contraction with temperature, so that their ground figure does not distort. I believe that Corning still makes the glass available for this purpose.

  2. Soda lime glass has 1/3 the temperature differential of borosilicate glass, if both are perfectly annealed.

    Soda lime glass has a temperature differential of 99 °F, yes only 99 degrees!!! Pouring very HOT near boiling drippings into the new soda lime Pyrex measuring cups can crack/shatter them.

    Borosilicate glass has a temperature differential of 330 °F,
    Pyrex oven dishes are made from this glass, and I hope they are still are. If that $30+ dish of organic lasagna, breaks, the manufacturer is going to get such bad reviews, that out-of-business looms on their failed 5-year plan.

    1. Unfortunately, Pyrex is NOT made from borosilicate glass and has not been for almost 20 years. If an item has a stamp or printed logo in all capital letters, it’s a safe bet that it’s borosilicate. Newer items have the name/logo in all lower case letters, and these are made from soda lime glass.

  3. Why does the print come off the measuring cups so fast now? I had them for years before. Now on the new ones I buy the print comes right off the cup Isn’t any good without the measurements. A senior

    1. Annette, if the print comes off quickly, you might have to buy more cups, and the company sells more product!?? Well, just kidding. I don’t know but I assume the ACL (applied color label) techniques being used on the newer measuring cups are different in some ways than the older type….that is, INFERIOR methods for producing a lasting image. …..it seems the best ACL graphics were during the 1940s-1960s (such as used on soda bottles, milk bottles, glass sugar and flour canisters, etc). Or maybe that is just a faulty observation of my own that doesn’t hold water.
      Sorry I have no definitive answer. Perhaps a reader can offer more solid feedback on this subject.
      ~David

    2. Thank you dear for answering, I always love Pyrex and always used the glass coffee pot for many many years. It just broke and I’m so lost with out it. I wish they were still making them like years ago. I don’t like the new machines they have. Now I love the smell of perk coffee on the stove. Oh well, nothing I can do about that now. Love, a senior.

  4. The glass was not tempered correctly. If you contact the company, I bet they’d replace it for you. The glass would have to be tempered at the factory and there is nothing in the environment that could cause this to happen on a piece of glassware that was tempered adequately. Extreme temps will only impact an untempered piece of glass.

    1. Hi Janet,
      Yes, proper tempering of glass does REDUCE, but DOES NOT competely ELIMINATE the chance of breakage. There have been hundreds of reports in recent years of this cookware shattering. Such things have happened over the years occasionally, but the frequency of the occurrences have greatly increased after the manufacturers changed their formula to a cheaper grade of glass. SO, whether or not the glass was properly tempered, it is a less durable grade of glass, not as strong and resistant to breakage as the original Pyrex formula was.
      The problem seems to be that the more recently-made Pyrex glass (distributed by World Kitchen) and it’s main competitor brand of cookware (manufactured by Anchor Hocking) are now made of a soda-lime glass instead of BOROSILICATE glass which was the original PYREX formula and which much more resistant to sudden temperature changes.
      From Consumer Reports, quote: “U.S. manufacturers of both Pyrex and Anchor Hocking have switched from borosilicate to soda lime glass for their glass bakeware”
      Please check out these webpages:

      https://www.techfragments.com/exploding-pyrex-cookware/

      http://pressroom.consumerreports.org/pressroom/2010/12/hot-glassware-can-shatter-unexpectedly.html

      Take care, David

  5. I had a Pyrex 4 cup measuring cup explode in my cupboard.I have had it for only about 8 months. What would have caused this?

    1. I don’t know, but assume it is a more recent, perhaps poorly annealed / lower quality glass. Even Pyrex can break if subjected to sudden EXTREMES of heat and cold within a short period of time.
      David

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