Is it Glass or Crystal?

Here REFLECTIONS takes a analytical look at some of the defining characteristics and historical developments of Czech glassmaking. From raw materials to glass appreciated for its striking clarity and brilliance artfully molded into complex forms for functional and decorative use. Crystal, the perfect carrier of pure light.

But which is it? Glass or crystal?

Quartz, in its' pure state resides as the elemental base of glass. Historically, quartz mined in the northern region of Bohemia was ground into sand (silica) and embodied with deposits of iron oxide for the purpose of producing normal glass for everyday usage. This type of glass carries a greenish tint which for example is evident when viewing machine cut, sheet glass panels from the side. When iron and other impurities are refined and additives of lead oxide (PbO) are combined with glass in its raw mineral form, the product is crystal. This difference in terminology is acknowledged due to the fact that the material outcome resembles a true and colorless form heavily contrasting the visible attributes of window panes and industrial glass products. Crystal denotes absolute clarity, brilliance, exceptional quality, hardness, and a complex material chemistry whether the composition contains lead or remains lead-free. The addition of PbO to a glass composite is known to increase clarity, brilliance and light refracting abilities; the color spectrum emanating from a finished product such as a cut crystal pendant that hangs from a chandelier, or a crystal vase viewed under a complimentary light source. In addition, lead oxide softens crystal, making it easier to manipulate but prolongs the amount of cooling time once the molten glass is removed from the kiln for the glassmaker to begin his/her work. In fact, compositions containing additional elements such as calcium, potassium, barium and lead oxide(though not all represented at once) all affect an object’s resistance to abrasion depending on the amount added to the mixture (the material composition is important for the artist to consider before she/he undergoes the process of melting, cutting or engraving).

Certain percentages of PbO may or may not be present within a workable composite and it is necessary to recognize possible existing quantities of this element before we can constitute it as either glass or crystal; however standards vary across countries.

According to European Union standards today, glass containing less than 4% lead oxide (PbO) is referred to as “glass” and a composition containing a PbO content above this percentage is “crystal.” American percentages differ slightly where pure glass must contain a PbO percentage of less than 1% and anything above is crystal. Commonly, crystal that contains a PbO percentage higher than 30% is called “high lead crystal.”

With respect to the evident differences between crystal and glass, the term crystal is often used in conjunction with the clarity of an object (the word crystal is derived from the Greek word krystallos meaning "clear ice"). Romanticism suggests that crystal can be perceived as pure water in perfect stillness with absolute clarity. Trade workers in Bohemia began blowing glass in monastery workshops during the 13th and 14th centuries. Consequently as popularity in Europe increased, the latter portion of the 13th century witnessed the construction of 20 glassworks in Bohemia and Moravia. Today there are more than 40 factories in operation. Products at this time within the line of functional, glass tableware were strictly reserved for members of high nobility as they installed glassmaking furnaces on their estates.

17th century Bohemian glassmakers had made progressive contributions to glass and crystal production by manipulating the chemical composition of molten glass. Their recipe would further be known throughout Europe respectively as Bohemian Glass. Considerably their creation consisted of potash-lime glass and calcium carbonate(chalk) responsive to a greater intricacy of complex engravings and cutting techniques than Venetian glass. It was now possible to produce crystal with an exceptional degree of hardness that could still be cut and artistically engraved. when a higher percentage of PbO is added, the result resides in a slight increase in weight (as opposed to glass in the absence of additives) and the enhancement of its brilliance and transparency. These complexities are very well represented across the line of Bohemian glass and crystal products today and can be considered an indication of Bohemian style artistry. Ruby glass, enamel-painted glass, and gold sandwich glass(gold fused between two outer layers of glass) are only several examples of popular products in the market today.

Glassmaking in the Czech Republic is a regional tradition that continues to be widely practiced by the growing generations here. Placement in today’s global market has proven this timeless style of artistry to be very successful and attractive to people across a wide array of cultural heritages on account of its beauty, craftsmanship, and elegant design.

Crystal and its rays of light connect us with the primordial absolutes that continue to persist in the world today. They invite us to experience creation.

Sources:

Foulds, Diane E., A Guide to Czech and Slovak Glass, European Community Imports: Prague, Czech Republic, 1995