This is one of those trick questions that pops up in the shop from time to time, and probably anyplace where glassware is sold. It applies to vintage lighting and contemporary creations. Trying to sort out the various designations of “crystal” brings up more questions. Is the question whether the prisms are lead crystal, a finer glass product, or are the prisms of rock crystal, actual quartz formations cut into prism shapes? Asking if these are “just glass” ignores things like Murano blown art glass creations, with their fanciful and colorful glass flowers and pendants.
Very early use of the the crystal drops on a metal lighting fixture was a way to bounce the light and lend a delicacy, sparkle and visual interest to a candle fixture. True rock crystal drops were one way to do this, but the scarcity of the material in quantity and the difficulty of working it made this an expensive option.
Over the centuries, as the glass making arts developed around the world, various artisans found different mineral combinations to achieve numerous desired glass properties. The addition of lead to the glass was particularly beneficial to making a sparkling product, since the mineral would refract the light internally. The “softer” glass that resulted could be polished or cut to enhance the sparkle. Fixture parts could be formed of fine lead crystal, either smooth and clear, or with cut designs, resulting in a particularly light, airy and brilliant all-crystal fixture.
Being able to determine if a given fixture is “crystal”, meaning lead crystal in this case, takes practice and seeing multiple examples of the various parts in varying qualities. Due to the modular nature of chandelier constructions, any given antique light fixture may have lead crystal prisms, pressed glass bobeches, blown glass arms and a mixture of pressed glass and lead crystal body components. This would still be called a “crystal” chandelier, but one would have to examine each part to determine the full extent of such a designation.
The lighting industry and glassware manufacturers are constantly revising and improving methods and materials for producing lighting prisms and parts. Until only recently, most inexpensive prisms were a pressed glass product that, while adequate, would not exactly be confused with true crystal. It is now possible to get prisms that are quite clear and sparkling indeed, yet these are not quite lead crystal but a finer grade of glass product.
When discussing crystal prisms one has to recognize the widespread influence of Swarovski/Strass crystal on the market. The prisms produced by this firm are a full lead crystal product, with that extra bit of surface coating to enhance the refractive qualities of the glass, and thus create an exceedingly sparkling effect. Adored by some and reviled by others as “glitzy”, such prisms have their place but are seldom found in traditional or antique lighting where they would alter the cohesive overall look of the vintage crystal chandelier.
In a final note on this discussion, to address the “just glass” part of this topic, we need to look at how large a role glass plays in the lighting industry. From the fanciful creations of the Murano artisans in Italy to the humble opal white schoolhouse light globe, much of the visual and functional appeal of lighting owes a debt to the glass industry. While it is still possible to get rock crystal chandelier drops (for a price), there is a world of variety of fanciful or colorful glass prisms or pendants to ornament a deserving fixture. Having the prisms of lead crystal is but one piece of a fixture’s overall design appeal.