Artificially Purpled Glass / Irradiated Glass / Surface-Stained Glass / Altered Glass
In recent years the practice of altering the color of glass has reached epidemic proportions, and is an increasingly confusing and undeniably damaging aspect of the subject of collecting antique or vintage glassware. The fields of American antique bottles, Fruit jars, Early American Pattern Glass, and antique glass electrical insulators have probably been affected by this trend the most, but other fields of collecting are increasingly being affected too.
There are several ways in which glass can be color-altered, but the most common, as well as problematic, and highly controversial, is the use of equipment that sends germ-killing X-rays or Cobalt-60 gamma rays through food (including fresh produce and spices), killing micro-organisms as part of increased safety procedures. This process of irradiation (often called “nuking”) has been rapidly increasing in use in the United States over the last few years.
Purple (Amethyst) Glass
Authentic purple glass has been made for many years, and has seen periods of rising and falling popularity, particularly as relating to glass tableware. Glass lumped under the term “purple” can range widely from a very pale lavendar, to medium shades of purple, to very deep royal purple, to virtual “blackglass” in which the color can only be seen when a very, very thin sliver is held up to a bright light.
Much of the “clear” or “off-clear” glass made during the 1880s-1920s contains the element Manganese, which was actually added to the glass “batch” as a decolorizing agent. The manganese helped to “mask” or “neutralize” the effects of iron which typically causes some shade of light green, blue-green or aqua color in glass.
Manganese, in somewhat higher quantities, also imparts a purple color to glass. When manganese-containing types of glass are subjected to later irradiation, the glass may turn various shades of purple. These shades may appear as an odd “grape-Kool-Aid” purple, a blue-purple (almost leaning toward a cobalt-blue color in some instances) or a very deep royal purple.
Glass containing enough manganese may NATURALLY slowly turn some shade of very light to medium purple after several years of exposure to the rays of the sun. This was frequently termed “SCA” (sun-colored-amethyst) or “desert glass” by bottle collectors especially in the 1960s and 1970s. In most cases the shade of color is quite light or “pastel”. HOWEVER, the artificial purpling of glass (especially when strong doses of irradiation is used) usually causes a darker or “peculiar” shade of purple to result.
There are several fields of glass collecting in which the scourge of artificially “purpling” glass has become really a serious problem, especially to those collectors who have a real interest in the preservation of the history and integrity of old glassware. This includes the field of what is called EAPG (Early American Pattern Glass) . Some of these pieces are artificially purpled and offered for sale at flea market booths and on online auction sites. Such items as water and milk pitchers, spoonholders, creamers, tumblers, salt cellars, sugar bowls, compotes, cake plates, oil lamps, and other forms of tableware in various patterns of the 1880s-1910s have been irradiated, and are sold to unwary collectors, or casual buyers merely looking for decorator items or something that “catches their eye”. Some of these buyers really couldn’t care less about the provenance or authenticity of the glass, thus compounding the problem. If/when the nuked glass is re-sold later on, the next purchaser typically assumes the glass was made that color in the beginning.
Although some purple glass was produced in a few EAPG patterns, very, very little of it was made originally, in comparison to the TREMENDOUS quantities of clear (or an attempt to be as colorless as possible) early American glass tableware.
Another field of glass collecting is the study and collection of antique bottles and flasks. Many of the more common types of clear glass bottles of the 1880-1920 period are now being mass-irradiated and sold at flea markets. If you spot a large number of old purple bottles (or jars) within a particular booth in a flea market or antique mall, you can be quite sure they have been irradiated, and were originally colorless, or nearly clear glass.
The perpetrators of this type of wholesale altering of glass usually (but not always) do this to alot of the more unremarkable clear glass bottles such as common druggist, soda, ink, chemical, whiskey and food bottles, sometimes those with no brand name or city on the face, and often examples that are completely “slick” with no markings at all.
It is very common for old purple bottles such as these to be dull and heavily stained with a whitish residue or “sickness” on the surface of the glass. This is a very strong indication that the bottles have been dug (the sickness caused by long burial) , were clear to begin with, and were later irradiated en masse. Contrary to what some sellers might say, there is no reason to believe that these bottles would eventually darken to that degree if they were left in the sun for a thousand years. The process of irradiation is not quite the same as ordinary sunlight, and it is more likely that the glass would never attain this dark of shade of purple if purely “sun-colored” naturally.
Some glass telephone insulators, and some bottles which were originally an aqua or light green color may be altered/irradiated to come out a purple color, and in some cases (depending on the exact chemistry of the glass and what ingredients were contained in the cullet used when forming the batch) a peculiar cornflower blue, dull gray blue, or sapphire blue may result.
(To make this even more confusing, many types of insulators are found in shades of purple glass that are known to be authentic __ as found __ for instance some of the W.F.G.CO. and W.G.M.CO. insulators from Denver; the AM TEL & TEL CO tolls; the Whitall Tatum CO. No 1; and many of the “Diamond” CD 102 ponies from Canada).
Clear glass that was originally decolorized by using selenium as the active ingredient instead of manganese (the use of selenium was particular prevalent in the 1920s and 1930s and later) may turn strange shades of “burnt amber” or “smoky dull dark brown” under irradiation, which are colors virtually unknown in the production of the original glass product. Just for an example: If you find an insulator marked “HEMINGRAY-42” and it is in a dark brown/amber color, it has been IRRADIATED! (No original Hemingray-42’s were ever made in such a color).
Recently, Coca-Cola and other types of soda bottles have appeared for sale online that have been irradiated, resulting in a peculiar ‘dull’ burnt brown shade. The original “Coke bottle green” (light green-aqua) has been changed to this sickly appearance.
Knowledge of exactly which colors are known in the various types of original insulators can be gained by studying value guides, along with searching for information on various webpages that delve into more detail on this subject. Sometimes, just the exact embossing arrangement (lettering on the glass surface) seen on a particular piece can make a big difference on whether a color is authentic or not.
“Stained Glass” / Surface-stained glass (this subject is not pertaining to the more commonly understood context of “stained glass” as relating to architectural or ornamental glass seen in church windows)
Sometimes glass (and this pertains especially to electrical insulators) is surface stained to achieve the appearance of a different color, typically an unusual color completely different from the actual color of the glass. This has become increasingly common on auction sites such as ebay. In many cases the description of the insulator is written in such a way as to deceive or confuse new or unsuspecting collectors who will assume a color is authentic or “all-the-way-through-the-glass” when it is merely a surface coating. A clear glass insulator of a common type with little monetary value may appear to be a much more valuable type by adding a surface coating!!! The color may be achieved by using some type of glass paint, and sometimes subsequent heating to cause the color stain to adhere more steadfastly to the glass. Thus a “one dollar” insulator may be wrongly assumed to be worth much more because the color is perceived to be “rare”. Most “serious” insulator collectors frown on this practice and encourage other hobbyists to learn more about what they are actually buying. Some online sellers may imply in their descriptions that this practice of surface-staining is ethical or highly to be praised, and that the buyer is just obtaining an unusually colored insulator to display in their window for mere decoration. There may be nothing intrinsically “wrong” with that, but the problem comes when the piece is RESOLD and the next person who gets it may have NO IDEAS on it’s provenance or whether or not the color is authentic and original. The insulator may be sold for a much higher price than it is worth, if either the seller and/or the buyer doesn’t understand that the color is entirely FAKE.
Here are some webpages that I would strongly recommend for more detailed information on this subject~~~
Artificially purpled Early American Pattern Glass:
Webpages concerning fake and altered glass insulators:
Fake colors in insulators:
Bottles — Irradiated Glass, the Color of Greed:
A nice reference book illustrating alot of purple glass:
Purple Glass: 20th Century American & European, a Schiffer Book for Collectors, (Leslie Pia, Ed Goshe and Ruth Hemminger) illustrates a wide variety of purple tableware and art glass, all (or virtually all) believed to be authentic and as originally made.
This page is under construction. I hope to add more photographs in the near future. THANK YOU for stopping by!
Please click here to go to my Home Page.
Click here to go directly to the Glass Bottle Marks pages (listings of marks used by glass companies / manufacturers on bottles and other glassware).