Czech glass: a history of grace and taste
Bohemian glass in the Czech Republic dates back to the days of the Celts, who once lived in the territory of modern Czech Republic. Glass jewelry has been found in this area since the 9th century. The glass factories themselves, judging by archaeological excavations, appeared in the second half of the 13th century, which are also mentioned in written sources from the 14th century. In the Middle Ages, the most important factor for the production of glass was the availability of sufficient quantities of wood and water. For this reason, glass factories were located far beyond the city walls, in border areas such as the Ore Mountains, the Izerské Hory, the Orlické Hory and Šumava.
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Glass production was considered primarily a privilege of the church. Especially the Benedictine Order, which has been making colored glass pieces for stained glass windows since the 9th century. Glass factories began to appear already in the 13th century in the border areas. The first glass factories produced simple glass for windows, later jewelry and finally hollow glass. Written sources from the 14th century contain contracts for the sale of glass, and the names of some cities and villages that exist to this day, such as Glaziers, Glass Factory, Old Glassblower.
In the Middle Ages, Bohemian glass was produced according to a special recipe by the monk Theophilus, which guaranteed a special quality. For this, two parts of beech ash and one part of silica sand were used. At first, glass was produced only as colorless or in a slight shade of yellow, green or brown. Until the end of the 13th century, Bohemian glass in Europe was considered a very rare and expensive product. Later, its production expanded to such an extent that they even began to export it outside the country. For example, around 1430, Czech jewelry began to be sold in Nuremberg and even in Spain.
Colored Bohemian glass
Medieval glassmakers were not only excellent craftsmen, but also designers and artists. Thanks to this, they did not have dependence on the owner and were always considered free people with special privileges. During the reign of Emperor Rudolf II from 1497 glassblowers were knighted and they could even receive the title of nobleman. And also in the 15th and 16th centuries, colored Czech glass began to be produced using different minerals:
● White color (milky white) - phosphorus, fluorine compounds, fluorite, fluorosilicon sodium
● Red - gold, golden ruby, selenium
● Black color (opaque glass) - manganese and chromium oxide
● Purple color - raw manganese (manganese dioxide), neodymium
● Blue color - cobalt, copper oxide, copper sulfate, neodymium
● Gray color (smoky glass) - nickel
● Green color - iron oxides, chromium in combination with uranium
● Yellow color - cerium with titanium, silver, uranium
What is the difference between glass and crystal?
Czech crystal is glass mass made from silica, soda and lead oxide. Czech glass is made from soda or potash, lime and silica and contains no lead oxide at all. Lead oxide makes the glass mass heavier, thicker and softer – which enables us to cut into it. It also increases the clarity and light refraction of glass mass. On the other hand Czech glass is thinner, more fragile and harder. That is why the Czech glass is not decorated by cutting, but rather by engraving and painting. In the USA glass, which contains more that 1% of lead oxide, is considered to be crystal. However, Bohemia or Czech crystal contains between 10 – 30% of lead oxide. Particularly our hand-made crystal contains 24% of lead oxide, which is the top quality. 30% crystal is too soft and it is used for some of the crystal trimmings only.
Colors like red and yellow did not appear until the 18th century. At the beginning of the 19th century, it was Czech glass blowers who had the greatest merit in glass production. At the same time, the production of crystal began, which was glass with 24% PbO content. In 1861, a grinding shop in Josefodol appeared under the name Bohemiae Caesar Crystal, which uses a unique technology of manually joining layers of transparent and white Bohemian crystal at a temperature of 800 ° C, which gives the crystal a unique color. To this day, the technology of Bohemian glass in this workshop has not changed - all products are made by hand.