Identifying crystal glassware is not as hard as it may seem. While there is not an exact process used to identify crystal glassware there are certain characteristics to look for, including intricate patterns cut into the surface (crystal glassware is softer than ordinary glass, allowing those patterns to be cut). Also, when held next to ordinary glassware, crystal will stand out because of its characteristic luster and slight grayish tint.
Wash each piece of glassware separately in warm water. To safely remove dirt, dust and smudges from the glass surface add one tbsp. of mild liquid dish detergent to the water.
Gently dry each piece of glassware with a soft cloth or paper towels until they are completely dry. Examine the glassware in a well-lit area to ensure that they are smudge-free.
Examine each piece of glassware, holding it towards the light. The crystal glassware will refract the light, producing a rainbow effect. Crystal glassware will also appear to glisten and sparkle more than the ordinary glassware. Ordinary glassware will not produce any effect.
Gently tap your fingernail against a curved area of the glassware. The crystal glassware will produce a clear ringing tone, which will continue to vibrate slightly for a short time. Crystal is heavier than ordinary glass, which causes the vibrations to last longer and produces a clearer sound. When the ordinary glassware is tapped it will produce a pinging sound, and it will not vibrate.
Hold the glassware in your hands and feel the weight of each piece. Notice the weight difference. Crystal is heavier than ordinary glass due to the lead oxide added to the glass during firing. The heavier a piece of glassware is (when compared to ordinary glassware of the same size) the higher the lead oxide content.
When buying crystal glassware be mindful that there is no internationally agreed-upon standard. In the United States, glass is defined as crystal if it contains as little as one percent lead oxide. Yet in Europe, glass must contain at least four percent lead oxide to be classified as crystal.
Be aware that many manufacturers label high-quality glassware as "crystal" even though the glassware contains no lead oxide.