Question

from Janet Ziffer of Columbia, MD

Dear Alan

The “problem” of clear glass taking a purple tint was not uncommon among the glass community of the first half of the 20th Century. But unlike John Styler’s example, most are more valuable if they are clear. This issue is often discussed relating to the glass tiles designed by Frank Lloyd Wright for the Luxfer Prism Company. The tiles themselves are not common, but it is rare to find one without some tint.

Although I never thought about the car mascots (and I collect a lot of Lalique), I read a lot about the purple tints when I was looking to buy a Luxfer tile years ago for my late husband who was an architect. But the same is true for a lot of clear glass. I have a Heisey pitcher that I bought to actually use. A cousin who is an antique dealer advised me not to display it where it would receive direct sunlight as it would take on a purple tint which would devalue it.

Searching the Web for the Color Purple

from John Styler of Prospect Heights, IL

I was so intrigued by this purple ( amethyst) phenomena I searched the web and found this info. No mention of Steuben or Lalique glass. see the following:

How it all got started–

Lead has been used for centuries as a clarifying agent in making glass. In the 1860’s the formulas for American pressed glass changed & lead (See article on flint glass) began to be removed from the mix & manganese was substituted to make the glass brighter and to act as a stabilizer.

In time, it was noticed that this glass made without lead but containing manganese was found to turn a very light lavender if placed in a sunny window or otherwise exposed over time to (ultraviolet) rays of the sun.

At some unknown point, antique dealers, no doubt beginning in the “Sunny Southwest”, learned that by setting their old glass out in the sand, on their rooftops, or wherever they could get a sunny exposure, they could turn the glass REALLY purple. If they set glass out and it turned purple, it proved to them and to their customers that the glass was, indeed, made prior to ca. 1915 when most, but not all, glass company’s ceased using manganese and substituted selenium as the clearing agent. Heisey, Duncan & Miller, Fostoria, Cambridge and Imperial glass companies are some exceptions.

But purpling glass in the sun took months to accomplish, even in our bright SW sunshine. As the demand by folks (who had no idea they were being sold ruined antiquities) for “sun-purpled” glass and the prices realized by the purpling dealers increased, an effort to speed up the purpling process was made. Because germicidal lamps emit ultraviolet rays which simulate those of the sun, great numbers of people began to buy glass that glowed yellow under a black light (see article), and subject the glass to the germicidal lamps (which didn’t set in the western skies in the evening wasting all that valuable purpling time).

The artificial process is so simple and the financial rewards are apparently so great that the practice has spread and grown to the extent that thousands and thousands of pieces of EAPG have now been turned purple and put on the public market.

The color change to purple is irreversible.

Following is an article first published in The Antique Trader, July 1994.

This Color Purple–

An Unnatural Disaster

There is a dilemma in the world of Early American Pattern Glass that needs addressing. It is the widespread practice, in the southwestern United States, of exposing EAPG to a germicidal black light for a few weeks or directly to the sun for an extended period of time thus turning the glass artificially purple. The merchandising MO is to buy old glass, do the exposure thing, take the pieces that turn a pukey light purple (some flint won’t turn), hike up the price, write a little purple flyer with a charming story about how the sun, over the past hundred years has reacted with a chemical, “magnesium” (sic), in the glass and created this glorious purple antique.

An, Oh My Gosh

from Gail P. Bardhan

Reference and Research Librarian

Rakow Library

The Corning Museum of Glass

Omitted by mistake in my response to the request for titles of books on Tiffany (which appeared in an earlier Gazelle Gazette)

Doros, Paul E. The art glass of Louis Comfort Tiffany / Paul E. Doros ; foreword by Alice Cooney Frelinghuysen ; photography by David Schlegel. New York : Vendome Press, 2013. 227 pages

The book provides a brief introduction to Louis Comfort Tiffany and his companies, with its primary focus on all types of Favrile glass, and mostly color illustrations.