Simple Tests Tell Age of Leaded Glass Shades

Antiques Roadshow appraisers make it look so easy. The television screen fills with a leaded glass lamp as the owner describes how he or she came to own it. No sooner does the owner complete the tale then the appraiser immediately pronounces the lamp “a genuine Tiffany,” “a superb Handel,” or in some cases, “sorry, it’s a cheap imitation.”

So what separates an authentic vintage leaded glass shade from a fake or reproduction? While it’s not possible to condense 20 years gallery experience the experts have into a short online article, there are a number of basic points about dating leaded lamps any one can learn in a few minutes.

All the finer vintage leaded shades made from about 1895-1925 were constructed in the copper foil technique. In this process, every individual piece of glass in the shade design has its edges wrapped in a thin layer of copper foil. The pieces are then assembled like a jig saw puzzle on a three dimensional form in the desired shade shape—such as a dome, flat umbrella, conical, etc. With each piece of foiled glass tightly touching each surrounding piece, molten solder is applied to the copper foil. The solder holds the shade together as well as produces the distinctive network of dark lines associated with leaded glass. It is the skill with which original copper foil shades were assembled that largely separates vintage shades from modern reproductions and most fakes.

The first test in evaluating shades is to closely inspect the quality of the leading, the soldered seams holding the pieces of glass together. Leading in quality vintage shades is uniformly consistent in width and height. The intersections of lines of leading are smooth and even. Where vintage shades are divided into straight-sided shapes, the corresponding lines of leading should also be straight; their edges meeting in straight and square joints. Vintage leading smoothly covers the entire piece of foil around the edges and the foil wrap should not be visible. There should be no gaps between the leading and the surface of the glass.

Fig. 1 Example of Line Leading
Fig. 1 Example of Line Leading | Source
Fig. 2 Example of Rim Leading
Fig. 2 Example of Rim Leading | Source

Leading in new shades can vary significantly both in width and in height and there are often obvious bumps where lines of leading intersect. New leading is often pitted and rough; obvious gaps in the leading are common. Straight-sided sections of new shades are often poorly fitted and the leading is substantially out of square and badly misaligned (See Fig.1 lineleading.jpg). The copper wrap is often visible in poorly leaded new shades and there are often gaps between the leading and the surface of the glass especially around the rims (see Fig.2 rimleading.jpg).

If you’re satisfied the leading is correct, the next test is to carefully inspect the glass. Virtually no copper foiled vintage leaded shade has survived with every piece of glass in perfect condition. Simply handling heavy leaded shades over the years creates subtle bending in the circumference which produces stress cracks. These occur primarily in the larger pieces of glass especially in longer thinner pieces where stress is the greatest. By contrast, newer shades, assembled with heavier wider lines of leading and having been handled less in their shorter life, rarely have any stress cracks in the glass.

Finally, check all leading for consistency of patina. The patina—generally a dark coloring applied with heat and some type of chemical of acid to the leading—should be virtually identical over the entire shade. True patina is produced by a chemical reaction between the patinating fluid and the lead. Patina is not a surface covering like paint but extends down into the lead. If the “patina” is flaking off the leading, it is most likely modern paint, not true patina.

All of the above tests can be performed without removing the shade from the lamp base or even touching the shade. If you want to handle or touch a shade, always ask the seller for permission. If buying online, be sure to request good quality close up photos. Sellers with vintage shades are always happy to demonstrate the authenticity of their merchandise to potential buyers.

Never rely on marks or signatures as a single test of age or authenticity. So many leaded shades—including genuinely vintage shades by other makers—have had fake Tiffany marks applied that marks should have the least influence on your judgment of age or authenticity.

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Comments 2 comments

Jacki 23 months ago

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