What is the difference between crystal and glass?
Glass, crystal, lead glass, lead crystal, lead-free crystal...You may see these words often on the labels of some glittering stuff. But indeed, do you really know what are they exactly and what is the difference between each other?
Overview of Glass and Crystal
Before delving into the key differences between crystal and glass, it is important to first define what they mean in popular culture. For starters, most people are not aware that "crystal" actually refers to "lead glass." Below is a quick chemical composition lesson as well as the different types of glass and crystal that can be found on the market.
Glasses are containers that are manufactured using glass. This term is often used for drinkware that may or may not have handles. Glass, as a raw material, normally refers to the soda-lime, which makes up over 90 percent of all the glass that is manufactured today. Below is a brief description of the chemical composition of the different types of glasses.
Soda-lime glass is made from lime, soda, and silica. This is the most typical kind of glass for light bulbs, windows, tableware, and figurines, among others. Because its components are readily available in nature, it is also the most inexpensive.
Borosilicate glass, or Pyrex, is composed of silica, boric acid, soda, and other additives. This kind of glass is often used in the laboratory and the kitchen since it is corrosion- and heat-resistant.
Fused quartz glass is made from melting organic quartz crystals in at high temperatures. This type of glass is typically used for laboratory equipment, halogen lamps, and high-end cameras.
When most people talk about bringing out the "crystal," they are often referring to a type of glass that is made from silica, lead oxide, soda or potash, and other additives. Lead crystal is prized for its durability and decorative properties. The term "crystal" is, by technicality, not an accurate term to describe lead glass, as being anamorphous solid, glass lacks a crystalline structure. The use of the term lead crystal remains popular for historical and commercial reasons. It is retained from the Venetian word cristallo to describe the rock crystal imitated by Murano glassmakers. This naming convention has been maintained to the present day to describe decorative hollow-ware.
In the European Union, labeling of "crystal" products is regulated by Council Directive 69/493/EEC, which defines four categories, depending on the chemical composition and properties of the material. Only glass products containing at least 24% of lead oxide may be referred to as "lead crystal". Products with less lead oxide, or glass products with other metal oxides used in place of lead oxide, must be labeled "crystallin" or "crystal glass". In the U.S., glasses with a lead monoxide content of 1 percent are automatically categorized as crystal.
How to Distinguish Between Glasses and Crystal
Aside from the chemical composition, which is not apparent at a glance, there are many ways to identify whether or not drinkware is made from glass or crystal just by observation. Listed below are some of the key differences of these two materials.
Compared to glass, fine crystal may be thinner or more decorative because the lead content lowers the working temperature of the glass, making it easier to sculpt. Normally, glass has to be fired to high temperatures with only a short window of time to blow or mold it. The presence of lead lowers the temperature and extends the working time, allowing crystal to be more ornately decorated compared to glass. However, while the presence of lead helps in sculpting it to the desired shape, it also makes the crystal more fragile, breakable, and prone to scratches.
Glasses, especially those made from soda-lime, are cloudy even when held up against the light. Crystal, on the other hand, is known for its clarity. This is why crystal is a popular choice for chandeliers, jewelry, and stemware. For wine lovers, crystal is preferred over glass because crystal drinkware allows for an easier appreciation of the color and viscosity of the liquid. The higher the lead content in crystal, the greater the clarity.
Similar to clarity, the crystal's refractive quality also has a great deal to do with its lead content. Fine crystal, particularly if it has a lead content that ranges from 36 to 70 percent, sparkles in direct sunlight. Optically clear crystal, another type that contains lead, goes a step further and is polished until it is blemish- and distortion-free. This type of crystal is known for the rainbow prisms it creates when placed under the sun. Glass, on the other hand, is more opaque.
Crystal is typically cut and polished in a precise manner. Additionally, it is also smooth to the touch. In contrast, glass tends to be brittle and sharp. One way to tell if a piece is crystal or glass is to feel the facets and overall design of the item. Crystal is much smoother than glass.
Another key difference between glass and crystal is the sound that it makes when tapped. Crystal produces a ringing sound like a "ping" when it is clinked. On the flipside, glass makes a low sound like a "thud."
The crystal's lead content also plays a crucial role in its weight. Because lead is a dense metal, crystal is naturally heavier than glass. One way to find out if the item is crystal or glass is to hold it. Glass is often lightweight, while crystal has a solid feel.
Potential Health Hazards
Most manufacturers do not advise storing food or liquid in lead crystal glassware due to the possibility of lead contamination. In fact, because of the health risks presented by lead, it is rare to find lead crystal wine glasses or alcohol decanters today. For those who are looking for lead-free crystal, some manufacturers use zinc oxide, barium oxide, or potassium oxide in place of lead to create a similar material. Lead-free crystal has nearly all the same qualities as lead crystal except that it is lighter and has less dispersive powers. Glass made from soda-lime, borosilicate, and fused quartz, on the other hand, pose no health hazards.
***Parts of above content quoted from eBay and Wikipedia***