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Copyright Rinker Enterprises, Inc. 1997
Reprinted with Permission

What’s Wrong With The Real Thing

During the past year I noticed the appearance in the secondary collectibles market of large numbers of glass objects, bottles, dinnerware, stemware, etc., with a light purple or lavender color. I recognized many of these as objects I typically encounter in a clear color. Since I had not seen them in this color variation previously, my curiosity was aroused.

When someone informs me that they had never seen an object before, my usual response is to question where they have looked. I immediately applied this to my failure to recognize these lavender objects.

However, I have spent years studying the color palette used on ceramics, glass, and other objects during different historical time periods. Recognizing the dominant and secondary colors that comprise a specific decade’s color palette is a very important authenticating tool. I have lost count of the number of museum visits I made where the only thing I focused upon was an object’s color.

If you place a piece of clear glass on a windowsill or shelf and expose it to sunlight for an extended period of time (usually only a few months), the color of the glass frequently will change, usually to lavender. Sunlight’s heat and ultra violet rays produce a change in the chemical composition of the glass. This is something I thought everyone in the trade simply knew. I now know this is not true.

Today’s collectors and dealers have a very poor understanding of how antiques and collectibles were collected and displayed during the past. Most individuals are so focused on the present and future that they have no time to study the past. Failure to understand past collecting and displaying patterns can prove costly.

Ceramics, glass, and furniture dominated collecting from the 1920s through the mid-1960s. Collecting and displaying a glass collection, whether bottles, drinking glasses (such as goblets or tumblers), or salts, was a favorite theme found in dozens of family and decorating magazines of the era. Several magazines suggested collecting glass by color. Blue (cobalt or aqua), red, green, and yellow (amber) were the popular colors. Readers were advised to construct shelves in their window wells or attached to the window frame so that natural sunlight would enhance the display presentation and show the "true" color of glass. They also advised adding interior lighting to corner and Dutch cupboards. I have never understood the thrill derived from excusing oneself to plug in a case’s lighting, especially when most of my recollections involve times when the system failed to function.

The color of any glass object is very much contingent upon the light source used to view it. Florescent light can change the visual appearance of the color of glass. This is why you will often see an individual thinking of buying a piece of glass ask permission from the seller to take it outside into the natural sunlight.

Those individuals who followed the advice of family and decorator magazines and exposed their prized glass collections to sunlight for a prolonged period of time eventually discovered that they had ruined their glass. As indicated earlier, clear glass developed a lavender hue. Some colors faded and not always universally throughout the piece. By the end of the 1960s, the only glass objects hanging in most kitchen or dining room windows were stained glass "objets d’art" (a polite way of referring to period kitsch or junk) or peace symbols.

Why this emphasis on color? Color plays a major role in the value of glass. Collectors search constantly for scarce colors. A slight color variation can double or triple the value of a glass object, provided, of course, that the color variation was created at the time of manufacturer and not artificially induced later.

Altering a glass object’s color is not difficult. Extended exposure to sunlight is just one method. The use of heat, chemicals, and irradiation are others. Unfortunately, as the 1990s end, changing the color of period and contemporary glass objects for financial gain is once again becoming a big business in the collectibles field. Some are doing it openly. A few unscrupulous dealers are not telling anyone what they are doing. The good news is that this latter group of sellers is so greedy that they cannot stop what they are doing once they have identified a potential new profit stream. As a result, eventually enough of their altered product appears on the market to cause alarm and lead to articles in trade periodicals identifying the problem pieces and the offenders.

The standard method used by individuals who want to change the color of clear glass to lavender is to place a large group of clear glass objects in their car trunk and leave the car outside in the sun for several months. Obviously, this works best if the alterer lives in the South or Southwest. Individuals who alter glass using this method do large quantities at a time. Often an entire booth or table is filled with the end products. While I have never seen a sign that says "Color Altered Glassware," there are more than enough examples to set off alarm bells. When another dealer buys a few examples and mixes them with his stock, the opportunities for abuse and deception increase significantly.

During a recent visit at Renninger’s Extravaganza in Mt. Dora, Florida, I ran across a dealer who had a table full of dark purple and blue glass objects. It was readily apparent that the initial color of the glass pieces had been altered. I assumed the dealer must have had the objects in his car trunk for a very extended period of time, a false assumption on my part. The colors of these objects were changed through irradiation.

I consider the $32 annual subscription to Antique & Collectors Reproduction News (ACRN, PO Box 12130, Des Moines, IA 50312) one of the best bargains in the collectibles field. Mark Chervenka’s pioneering work in documenting reproductions (exact copies), copycats (stylistic copies), fantasy items, and fakes is laudable. Mark is at his best when he plays detective.

The December 1997 issue (individual copies $4.95) contains an excellent article on how irradiation is being used to alter the color of glass. While fact filled, I found two issues in the story particularly disturbing: (1) manufacturers are now using this technique to alter glass color during the course of manufacture and in attempts to sell slow moving stock and (2) at least one author has included illustrations representing altered pieces as originally manufactured colors in a recent book he published. There is a blind acceptance by most readers of the information found in trade literature, a fact the unscrupulous have no qualms using to their advantage.

Mark notes that the problem of color altered glass is spread throughout the field—from fruit jars to Lalique. The difficulty is that only laboratory testing, at a per time cost of $125 or more, can determine if a piece has been irradiated. The individuals who are selling color altered glass are banking heavily that the vast majority of buyers are either ignorant of this avenue or unwilling to pay the cost to use it.

Michael Guthrie’s A Handbook For The Recognition & Identification of Fake, Altered, and Repaired Insulators (published by author: 1988; 18 pages) provides excellent documentation of the color alteration problem faced by the insulator collector. It is an excellent what the problems are and how it was done handbook. Unfortunately, it also is a how-to book for the unscrupulous. Guthrie’s current address is: P.O. Box 130, Kalama, WA 98625-0200. Write or e-mail him at to see if he has copies available and at what cost. I also recommend visiting www.insulators.info, one of my favorite Internet web sites.

I am concerned about the short, intermediate, and long-term affects the appearance of color altered glass will have on all categories of glass collecting. More than ever, it is critical when buying glassware to insist on a "money back, no questions asked" guarantee.

As happens all too often, the field will enjoy a heightened awareness of the problem over the next several months. However, it is highly unlikely that this same level of awareness will exist five, ten, or fifteen years from now. The person facing the greatest danger is the collector of 2017 and beyond. I earnestly hope collectors will have learned by that time that it is essential to keep an eye on the past in order to collect intelligently for the future.

Questions and Answers

READER RESPONSE: Ron Barlow, owner of Windmill Publishing Co. (2147 Windmill View Road, El Cajon, CA 92020) wrote in response to my comments on sun-colored glass. He informed me that the basic glass formula was changed in the 1930s and glass made after this period will not discolor when exposed to sunlight. A photocopy of Chapter 13, "Decoloring and Sun-Colored Glass," from Cecil Munsey’s Illustrated Guide to Collecting Bottles (Hawthorn Books, 1970; out-of-print) accompanied his letter. Munsey notes:

"Both manganese and selenium oxides act as neutralizing agents, masking the light green and blue colors caused by the inherent impurities in the raw ingredients with a complementary color. Both of these decolorizers produce yellow, red, and purple while the iron impurities produce blue and green. The mixing of these opposite colors results in a neutral color which has the visual effect of no color at all.

"The use of selenium continued until around 1930, when arsenic became the popular decolorizer.

"Unknown to, or at least disregarded by, glass manufacturers using manganese and selenium, was the fact that when decolorized glass is exposed to the ultraviolet rays of the sun it assumes an amethyst color if it contains manganese or a light amber color if it contains selenium. This reaction is explained by the facts that when the decolorizers were added, the ions within the substance were in a reduced state and when exposed to ultraviolet rays they are put into an oxidized state...

"The amount of color decolorized glass will assume depends on two variables: (1) how much of a decolorizing agent was originally used; (2) how long the glass has been exposed to ultraviolet rays."

Harry L. Rinker welcomes questions from readers about collectibles, those mass produced items from the twentieth century. Selected letters will be answered in this column. Harry cannot provide personal answers. Photos and other material submitted cannot be returned. Send your questions to: Rinker on Collectibles, 5093 Vera Cruz Road, Emmaus, PA 18049.

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Last updated Thursday, June 11, 1998