“Is this glass or is it crystal?” she asked, pointing at a chandelier lavishly dressed in prisms. Welllllllll, prior to the early 1600’s, glass always had some color to it. In the 1630’s, artisans in Bohemia developed a technique for clarifying glass. This new, clear glass was referred to as crystal glass, “crystal” meaning “clear.” Within five years, crystal glass was the rage. People replaced semi-precious stones on their chandeliers with this fabulous new crystal from Bohemia. Not until sometime in the late eighteenth century was lead discovered to help clarify the glass even further. From then on, lead crystal was differentiated from the more common crystal. Besides clarifying the glass, proper lead content improved light refraction and made cutting and polishing the crystal easier. So, the answer to the lady’s question was “Yes.” It is glass, and it is crystal, as it is clear glass.
The real question regarding crystal is how to evaluate its quality. Basically, there are three tests for crystal:
1) How clear is the crystal? If it is as clear as a new piece of window glass, with no bubbles or distortion, then it is better crystal.
2) How sharply defined are the edges of each facet? The finer the crystal, the sharper the edges. That edge should be as sharp as a paring knife.
3) How well does the crystal refract light? Sunlight passing through a fine crystal prism should break into the colors of the rainbow, casting those colors onto the wall beyond the prism. Lesser prisms will have little or no refraction.
A difference in the production of crystal that impacts the quality is how the prism is polished. Prisms are made of cast glass, and must be polished when they come out of the mold. Fire polishing is the least expensive and least effective method, leaving the prisms slightly distorted and with dull edges. Hand polishing produces a cleaner surface and crisp edges. This technique involves holding each facet of the prism against a spinning wheel of very hard material, originally wood, but now of an even harder man made material. Old wood polished prisms are often of amazing quality and are the result of artisans spending time perfecting each piece. Today, a third method involves expensive automated machinery. It is technically the most perfect crystal but lacks the romance of that which is hand worked.