How Crystal Differs

The presence of lead in crystal softens the glass and makes it more accessible for cutting and engraving. Lead increases the weight of the glass and causes the glass to diffract light.. Lead crystal is made from a mixture of sand, potash (potassium carbonate) and lead oxide. The components are heated to at least 2,400 degrees Celsius until molten and red-orange in color.

The temperature is then slowly reduced to the "working" temperature.Glass can contain up to 40% lead, if maximum hardness is desired. On the other hand, crystal can contain less than 24% lead if it has a high proportion of barium oxide, which ensures high quality light diffraction.

The main difference between glass and crystal is the lead content. Glass is composed of sodium and potassium. Crystal is also composed of sodium, but in addition, it contains silicone, and has a lead content of 10-24%.

The lead makes the glass heavier and, most importantly, the lead changes the refraction index of the item, which makes it appear brighter and cleaner. Because the refraction index is higher and lead crystal is not as brittle as standard glass, it is possible to make deeper and more complicated cuts in crystal.

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To deserve the name “lead crystal” the glass must meet 3 criteria defined by rigorous rates and percentages . Below these measures, one can only talk about “crystal glass” or “crystalline”.

 
Metallic Oxides
Density
Refractory Index
Full lead Crystal 30%
PbO > 30%
> 3.00
> 1.545
Lead Crystal 24%
PbO > 24%
> 2.90
> 1.545
Crystal Glass, Crystalline
(Cristallin in French)
ZnO, BaO
PbO, K2O
Separately or together
> 10%
> 2.45
> 1.520
Crystal Glass, Crystalline
(resonant glass in French)
BaO, PbO
K2O
Separately or together
> 10%
> 2.40


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Learn more About Jade:

History of Jade
How Jade Differs
How to Make Jade Jewelry
How to Identify Jade Quality
How to Care For Jade Jewelry

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