![Glass and Crystal<br />There are all kinds of glass we see or use in every day life. We are so familiar with them that little attention is paid on them. Never the less, one must be deeply impressed by sparking wine glasses or brilliant chandeliers. These are made from crystal: a special type of glass.<br /> Crystal is a high quality, clear and colorless glass with high lead content. Ordinary glass mainly contains 60%-75% of silicon dioxide, 12%-18% of sodium compound and 5%-12% of calcium oxide. Crystal mainly contains 54%-65% of silicon dioxide, 18%-38% of lead oxide, 13%-15% of sodium or potassium. The international standard of crystal is 24% of lead content. <br />The presence of lead changes the density, viscosity, softening temperature and refractive index. Firstly, crystal is heavier, denser than glass. Secondly, crystal has a lower softening temperature. Its working temperature range is 600-800 degree Celsius. Glass is up to 1100 degree Celsius. In addition, crystal is about 100 times less viscous than glass at working point. This makes crystal much easier to be shaped and manipulated. The most important difference is that crystal has a higher refractive index than glass. Ordinary glass has a refractive index of n=1.5, while crystal’s refractive index is 1.7. This index measures the degree to which a medium separates light into its component spectra. So crystal can refract light into rainbow colors. This is why crystal looks brilliant and sparkling. <br />Because of the beautiful nature, crystal is mostly used for making jewelries, sculptures, miniatures, chandeliers and Christmas ornaments. It can also be used for drinking glasses and serving dishes. However, its high lead content may potentially poisons. <br />Crystal and glass may sometimes look similar, however, they have different features. I did many readings and researching. I think this topic is very interesting. It is a good experience and I enjoyed on it. <br />THANK YOU<br />Bibliography:<br />,[object Object]](https://image.slidesharecdn.com/glassandcrystal-100330195423-phpapp01/85/Glass-And-Crystal-1-320.jpg)
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- 2. Author unknown. “Lead glass” Wikipedia. Las revision date: 30 November 2009 at 11:00. http://en.wikipedia.org/wiki/Lead_crystal
- 3. Author unknown. “Glass” Lenntech. Last revision date unknown. http://www.lenntech.com/glass.htm
- 4. Hinders, Dana. “What is Lead Crystal?” wiseGeek. Last revision date: 26 August 2009. http://www.wisegeek.com/what-is-lead-crystal.htm