To judge clarity and luster, hold the piece against a pure white background. Good glassware is clear and tint-free, while inferior grades show cloudy bluish or greenish tints.
That doesn’t mean high-quality crystal is always colorless. By adding mineral salts to the mix of raw materials, glassmakers have been able to produce a variety of rich, vibrant colors that can greatly enhance the beauty of a table setting. Additionally, quality glassware will have a permanent polish or luster that results from fire polishing.
Glassware edges should be smooth, never rough or scratchy. In hand-cut glassware, the design should be sharp and accurate. In etched pieces, each tiny detail should be distinct and defined.
Some people also judge the quality of crystal by its ring. Hand-blown glass containing lead exhibits a clear ring, almost a musical tone, when struck lightly. Soda lime glass, the kind used for windows, does not have this resonance.