A brief history of glass
Glass beads and decorative items have been found in excavations of early civilisations dating from about 2500 BCE. By the 1st century BCE, the forerunner of modern glassware made its appearance in Alexandria. It is thought that the technique of blowing molten glass through a tube first started in Syria.
Glass was produced on a large scale in Venice, Italy, from the 7th century CE. The industry was later shifted to Murano. Murano became famous for its artistic glassware, and also for the production of clear, colourless glass. This type of glass resembled natural crystal and was named cristallo.
In 1675, George Ravenscroft introduced a new type of glass in England. It was called flint glass because calcined flint was used as its base. It deteriorated after a while, so lead oxide was used to correct this. It became known as crystal glass. This type of glassware was heavier and clearer than the ordinary glasses. It sparkled and shone attractively, and demand for this new product grew.
In the early 20th century, the Steuben Glass Company became famous for its delicately coloured crystal items. The ownership of the company changed, but the name Steuben was remembered for its exquisitely crafted crystal decorative pieces.
Waterford Crystal is another well- known producer of crystal ware. They have a quality control standard for the classification of crystal glass. Their criteria are: more than 24% lead content, density of more than 2.90 and a reflective index of 1.545.
Types of glass produced today
Soda lime glass is made from soda, lime and silica.
Borosilicate glass is also called Pyrex. It is made from boric acid, soda and silica.
Fused quartz glass is made from melting quartz crystals.
Crystal glass today
Crystal glass was used to store liquids. At that time, people were not aware of the hazards of lead poisoning. We now know that lead is leached into liquids from items that have a significant lead content. This can cause gout and other illnesses, some of which may be fatal. Many manufacturers have cut out the use of lead in crystal ware. Modern crystal is usually made with zinc oxide, barium oxide or potassium oxide instead. Crystal ware containing lead is still in use; indeed, it is still highly prized. But it is not used for storing liquids. It is considered to be safe if used for short periods of time.
A comparison of glass and crystal
- Glass is usually made from lime, soda and silica. Crystal is a type of glass which contains lead. Fine crystal contains at least 24% lead.
- Due to the addition of lead, crystal ware is heavier than regular glassware.
- Crystal sparkles much more than glass.
- Crystal acts as a prism. If the glass is held to the light, it breaks up into the colours of the rainbow.
- Crystal is often much thinner than ordinary glass because it can be worked on at lower temperatures.
- Crystal produces a ringing, musical sound when it is struck.
- Crystal is smoother to the touch. This can be perceived easily on the engravings. The sharpness at the edges of engravings is evident on glass, whereas on crystal it feels more rounded.