Many times on the web, especially on auction sites, we see beads described as 'crystal' that we would call 'glass'. The biggest category that gets mis-described this way is
Czech Fire Polish beads. They are glass, not crystal, as we detail below.
Regular glass is mainly made of Silicon Dioxide (SiO2), with the addition of other ingredients, such as sodium carbonate (Na2CO3), calcium oxide (CaO), magnesium oxide (MgO) and Aluminim Oxide. The resulting glass contains about 70 to 72 percent silica by weight and is called a soda-lime glass. Soda-lime glasses account for about 90 percent of manufactured glass.
In general, man made 'crystal' is a glass that has had one or more of certain minerals added to a standard glass formulation to make the product more brilliant. Lead is the mineral of choice here, as lead oxide added to the molten glass gives lead crystal a much higher index of refraction than normal glass, and consequently much greater "sparkle". The presence of lead also makes the glass softer and easier to cut.
As far as we know
Swarovski crystal beads have the highest lead content of any bead that can be called crystal. The design of the cuts is also important, just as in cutting gemstones. At Swarovski, the angles of the facets are set up to maximize refraction and reflection of light, thus making their products as brilliant as possible. One thing you may have noticed is that the more facets on a cut bead (of any kind, crystal or gemstone), the higher the price. However, the more facets, the more brilliant and pretty the bead, so you get what you pay for.
The Czechoslovakian companies, such as Preciosa, make quite nice crystal beads, but they do have a lower lead content, and less modern cuts. Thus, they are not quite as brilliant as Swarovski products. Also, the Czech companies are not as aggressive in constantly creating new cuts, colors and finishes, as Swarovski has been for the last few years.
Czech glass beads, as opposed to Czech crystal beads, are just glass, with no special mineral additives. They are lighter, and are often molded or 'pressed' into creative shapes.
Czech Fire Polish beads are glass beads (NOT crystal) that are cut into faceted shapes. However, the cuts are imprecise, and there is no mechanical polishing done. Instead the roughly cut glass beads are heated in special ovens. The surfaces and cut edges melt a little in the heat and smooth out nicely. The beads are then removed before they melt down entirely (we have seen some half-melted ones, just little bubbled lumps, it was amusing). Special coatings are applied after this stage.
A word about Chinese "crystal" beads. Humph. We have our doubts. They are super light weight, which alone indicates an absence of significant mineral additives. Their faceting is minimal, so this adds to their lack of brilliance. Yes, they are inexpensive and colorful. They are excellent for projects for young people. Are they really 'crystal' glass, or just regular glass? Who knows? Accept them for what they really are, and you won't be disappointed.
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