![]() When manganese-containing types of glass are subjected to later irradiation, the glass may turn various shades of purple. Manganese, in somewhat higher quantities, also imparts a purple color to glass. Those two elements are easily confused because of their similar-sounding names). The element used as a decolorizer is indeed Manganese, NOT magnesium. (Note: sometimes the element referred to here is erroneously called “MAGNESIUM” by glass collectors and writers. The manganese helped to “mask” or “neutralize” the effects of iron (a normal impurity in nearly all sands used for glassmaking) that would otherwise result in some shade of light green, blue-green or aqua color in the finished glass. Much of the “clear” or “off-clear” glass made during the 1870s-1920s contains the element Manganese, which was intentionally added to the glass “batch” as a decolorizing agent. ![]() ( Note: Some purple tableware and art glass may have achieved its color from the use of nickel oxide, not manganese which was the main ingredient used in older glass bottles). ![]() Glass lumped under the term “purple” can range widely from a very pale lavender or lilac, to medium shades of purple, to very deep royal purple, to virtual “black glass” in which the color can only be seen when a very, very thin sliver is held up to a bright light. This process of irradiation (often called “nuking” by glass collectors) has been rapidly increasing in use in the United States and other countries over the last few years.Īuthentic purple glass has been made for many years, and has seen periods of rising and falling popularity, particularly as relating to glass tableware. 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 meat, fresh produce and spices), killing micro-organisms as part of increased safety procedures. The collecting fields of American antique bottles, fruit jars, Early American Pattern Glass (EAPG), and antique glass electrical insulators have probably been affected the most by this trend. 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. Irradiated Glass / Altered Glass / Artificially Purpled Glass
0 Comments
Leave a Reply. |