K9 is a Chinese Optical Borosilicate Crown Crystal (Optically Clear) with low inclusions and imperfections ideal for use in lenses and prisms, optics and decorative crystal lighting. It has good physical properties and can be polished similar to lead crystal, weighing approximately 15 percent less than full leaded crystal having a lead content of only 10 percent. K9 crystal offers a high refractive index and high clarity making it a good option for the manufacture of high end chandeliers offering both durability and excellent quality.
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, even if it does not necessarily possess a crystalline structure. It is referred to as crystal because, years ago, the Italian term “cristallo” was used to refer to Murano glass imitations. Lead crystal is the type that is most commonly used for wine glasses and other decorative ornaments around the home. In the U.S., glasses with a lead monoxide content of 1 percent are automatically categorized as crystal. In Europe, on the other hand, crystal is defined as crystal with a lead content that ranges from 10 to 30 percent.
Glass, 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.
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 when polished and distortion free. This type of crystal is known for the rainbow prisms it creates when placed under a light.
Crystal is typically cut and polished in a precise manner, 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 will be much smoother than glass.