| Natural glass, like obsidian, is a dense volcanic | | | | was progressively refined over the years. |
| glass, and has been used by man for millennia. To | | | | During the 11th century new ways of making |
| early man, obsidian glass was an extremely rare | | | | sheet glass came about in Germany. Glass |
| and valuable commodity, Because of the way | | | | blowers would blow spheres, and then form them |
| volcanic glass fractures, sharp edges occur. This | | | | into cylinders. They would cut the glass while still |
| inherent quality of natural cut glass was put to | | | | hot and then flatten the glass into sheets. Glass |
| use and was often made into sharp spear points | | | | makers in Venice, Italy improved this method in |
| and blades. | | | | 13th century. By the late 1300's there was as |
| Man-made rudimentary glass was made from | | | | many as 20 glassworks in Bohemia and Moravia. |
| silica sand, plant ash and lime. Over time it was | | | | The 12th century saw the arrival of stained glass |
| discovered that if glass was heated until it | | | | production. Stained glass, another form of colored |
| became semi-liquid, it may be molded or shaped | | | | glass, was made by adding metal impurities. |
| and left to cool into a solid new piece or vessel. In | | | | Church and monastery applications of stained |
| ancient times glass pieces were valued as a | | | | glass can be traced back to examples that remain |
| substitute for precious stones or gems. | | | | today, i.e. St. Bartholomew church in Kolin. A glass |
| During first century BC, the craft of melting and | | | | wall mosaic is preserved there from around 1380. |
| blowing glass into useable objects was developed. | | | | Venice became the dominant center for |
| Glass pieces and items gradually became more | | | | glassmaking during the 14th century. Here new |
| common after the discovery of glassblowing. | | | | glass making methods were developed and |
| Objects such as vases, bottles, and cruets were | | | | export trade such as mirrors, tableware, and |
| mouth blown and mold blown during the Roman | | | | decanters flourished. Secrets of glass making |
| Empire, usually for ordinary purpose and daily use. | | | | were highly guarded in Venice, but eventually glass |
| Common glass normally has a greenish hue. The | | | | workers moved to other areas of Europe taking |
| green tint is caused by miniscule amounts of iron | | | | their knowledge and skill with them. |
| impurities in the sand used to make glass. Glass | | | | A technique called "the Crown glass process" was |
| producers learned to make decorative and | | | | used to make glass until the mid part of the |
| colored glass by adding metallic compounds and | | | | 1800s. A glassblower would spin around 9 lbs of |
| mineral oxides such as cobalt. Colored glass of | | | | molten glass at the end of a rod until it spread |
| reds, blues and greens became prevalent. After | | | | out into a flat disk nearly 5 feet across. The glass |
| craftsmen learned to score and cut glass, they | | | | disk would then be cut into panes. Glass from |
| found clear glass refracted light in spectacular | | | | Venice was highly prized for over four centuries |
| fashion. Thus, clear cut glass became popular, and | | | | as they managed to keep this technique secret. |
| demand for colored glass plummeted. | | | | In 1688, a method for casting glass was invented. |
| Around 1000 AD, a new development was made | | | | This led to glass and glass panes in becoming a |
| in glassmaking. The glass making component of | | | | much more common material. The glass pressing |
| soda-lime, was replaced by potash obtained from | | | | machine was invented in 1827 and facilitated mass |
| wood ashes. From this time on, glass from the | | | | production of relatively inexpensive glass items. |
| northern part of Europe differed greatly from | | | | The glass pioneer, William J. Blenko, is recognized |
| that made in the Mediterranean area, where | | | | as first glass producer in America to use the |
| soda-lime remained in common use. Centuries | | | | cylinder method of creating flat glass by the |
| later in Bohemia, ashes from beech trees were | | | | 1920s. |
| used. The production of Bohemian "forest glass" | | | | |