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Arts & Antiques by Dr. Lori: How to Tell Crystal from Glass


Dr. Lori

Star Appraiser on the hit TV show Auction Kings on Discovery Channel.

Lori Verderame on Google+
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crystal

Crystal dish by the French collectibles firm, Lalique.

When it comes to glassware, most people think that the best way to spot quality is to “ting” a glass and listen. If you educate your eyes to spot a high quality piece of crystal, you can give your ears the day off. Why? The sound of a ting from a piece of glass is subjective and may not actually tell you anything about the quality of that piece of stemware. The idea that a high pitched sound will result in the identification of a high quality and valuable piece of crystal is not always the case. Just because a piece of glass sounds good when you ting it does not mean it is a piece of valuable crystal.  Other factors need to be evident to determine if you truly have the real thing.

Here are the facts. Glassware (traditional soda-lime glass) contains about 50 percent silica (sand) and no lead. Crystal contains at least 24 percent lead. That is the basic distinction between crystal and glass. Sounds easy enough, but it isn’t that easy. You remember your mother telling you that nothing worth having is ever easy.

Most people do not think that their everyday orange juice glass is a piece of crystal. Most of the time your everyday orange juice glass is made of a material called soda-lime glass — the glass in our everyday world. It is used for products such as windows, everyday drinking glasses, etc. Most glass made in the United States today is made of soda-lime glass which is a combination of lime, silica (sand), and soda. This is cheap everyday glass. No harm, no foul, no big investment.

On the other hand, borosilicate glass — called Fire-glass in the early 1900s and now called by its brand name of Pyrex — is a heat- resistant glass that does not break when exposed to extreme temperature changes. It is more expensive than soda-lime glass. Pyrex was first introduced for the windshields of railroad trains in order to stop window breakage when trains experienced a severe change in weather conditions. Borosilicate glass is mainly used in laboratories and does not easily corrode. Neither soda-lime glass or borosilicate glass is considered crystal because they do not have 24 percent lead content.

Crystal is made of silica (sand), lead oxide, and soda and is known to be beautiful and strong. Crystal is a term used to describe any glassware that looks fancy or is used in the service of champagne, wine, or spirits. Crystal is the choice for spirits and wine connoisseurs because it allows the drinker to assess the color and viscosity of the wine or liquor. If your piece of crystal is very clear, it probably has a greater amount of lead content than its cloudier counterpart. When it comes to crystal, its reflective quality and the 24 percent lead content are most important characteristics. Crystal shows more clarity than a typical piece of soda-lime glass and its reflective quality is why crystal is used for chandeliers, fine wine glasses, and jewelry pendants. Very fine crystal — like those pieces made by high quality firms such as Waterford — may even exceed the 24 percent lead content requirement and provide products that are upwards of 30 percent or more.

The confusion surrounding crystal is based in history and chemistry. First of all, despite its name, crystal does not have a crystalline structure. And, crystal is a term (cristallo) which was coined by Italian glassmakers in the famous Murano glassblowing center near Venice to define quality glassware which did not meet the European lead content standard. Crystal is typically thin because it is easier to sculpt glass with a high lead content because the lead lowers the working temperature of the glass. The lead extends the time that the glass blower has to sculpt a piece.

Tips for telling the difference between regular soda-lime glass and crystal:

Crystal has the following attributes: 24 percent lead content; bright reflective quality; clear overall appearance; silver or silver/purple color hue; rainbow prism effect when held up to the light; thinner and heavier than regular soda-lime glass.

In fact, high quality crystal with a lead content over 35 percent will actually sparkle. If you are trying to tell if you have a piece of cut crystal, place your thumb into the incised or cut design of the piece and move your thumb around — if you feel as if you will get cut, then you have a piece of cut crystal. Crystal will take on the properties of sharp cutting.  Fine glassware may contain some lead content but if the 24 percent lead content level is not reached for a specific piece of glassware then a manufacturer cannot by law call that piece “crystal.”
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Dr. Lori Star Appraiser on the hit TV show Auction Kings  on Discovery Channel.

Ph.D. antiques appraiser, author, and award-winning TV personality, Dr. Lori presents appraisal events nationwide. Watch Dr. Lori appraise antiques on Discovery’s hit TV show, Auction Kings airing Wednesdays at 9 p.m. Learn about your antiques at www.DrLoriV.com or call (888) 431-1010. Visit her Facebook at: Facebook.com/DoctorLori


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