Glass

• Glass is a material that has been produced for thousands of years. It was once much less common than today and considered a very precious material. Glass is made mainly from silica, or sand. Ordinary glass made from sand is typically green in color because of iron impurities. Different materials can be added to glass to change the color or the properties of the glass, which may change the appearance or the hardness and strength.
  
  

Lead Oxide

• Lead crystal was invented in 1676 by a man named George Ravenscroft. Lead crystal is glass that contains lead oxide. This addition has several desirable effects on the properties of glass. The lead makes glass more brilliant and sparkle more brightly. It also makes glass softer, which means it can be easily cut. Cutting crystal leads to a variety of beautiful effects, and faceting makes the glass resemble rock crystal.
  
  

Percentages

• The percentage marked on a lead crystal item refers to content of lead oxide it contains. Typically, lead crystal items range from 24 to 32 percent lead oxide. Thirty-three percent is the highest percentage of lead crystal. Higher percentages of lead give lead crystal more brilliance but also make the material softer. This means it is more difficult to work with in raw, molten form. More skill is needed to work with crystal with a higher lead content.
  
  

30- and 33-Percent Lead Crystal

• Thirty-three-percent lead crystal is the softest, most brilliant type of lead crystal available. It is also the most expensive type. Thirty-percent lead crystal is harder and duller but also less expensive and contains less lead, which may be desirable in tableware. Lead crystal, although beautiful, poses a health risk because of lead leaching into items intended for consumption. For example, a person may store an alcoholic beverage in a lead crystal decanter, and the lead from the decanter will leach into the beverage, posing a health risk.