by Frank Fulton
Originally published in Glass Canada Magazine, February 2019 Issue
This column so happens to mark the 10th anniversary of yours truly.
This column just so happens to mark the 10th anniversary of yours truly penning You Bet Your Glass for Glass Canada magazine. One of my favourite columns over the years was also one of my first, entitled “Glass For Dummies” in the April 2009 edition of Glass Canada.
It was full of interesting information about the history of glass. I bet you’ve either forgotten everything by now, or never read it in the first place. So, it is with pleasure that I bring you some excerpts from this timeless piece.
Glass is roughly composed of 70 per cent silica sand, 13 per cent lime, and 12 per cent soda. When heated to about 1,500 C, this mixture turns into a thick molten mass like molasses on a cold day. Some definitions refer to glass as an “amorphous solid.”
Like many great inventions, glass was first produced by accident in about 5,000 B.C. when a crew of Phoenician sailors transporting blocks of soda landed ashore on a beach near Belus in Asia Minor. When it came time to eat, they couldn’t find any rocks to put their cooking pots on so they improvised and used blocks of soda to support the pots over the fire. Once the fire got blazing, the sand and soda created a pool of molten glass.
Around 1,500 B.C., Egyptians discovered how to produce goblets and small bottles by repeatedly dipping a silica paste core on the end of a metal rod into molten glass, then later removing the core. At some point around 250 B.C., Babylonians began using hollow metal rods for this procedure and stumbled upon glass blowing. As a result, producing bowls, bottles, and cups became relatively much easier and less expensive, and the Romans’ demand for glass products as status symbols skyrocketed. Demand throughout the Roman Empire in many ways lead to the birth and growth of the glass industry. There is even evidence that crude cast glass was tried in some important Roman buildings and villas, but mostly the rich used thin, translucent sheets of alabaster to enclose wall openings. Unfortunately, with the demise of the Roman Empire, the fledgling glass industry stagnated for almost a thousand years and almost disappeared.
The 11th century saw the birth of the flat glass industry. German glass craftsmen are reported to have developed a technique, further developed by Venetians in the 13th century, where molten glass was blown into an elongated balloon shape, cut and flattened. This produced what was known as broad sheet glass. For the next 600 years, most flat glass was produced from flattening out blown glass in one manner or another. Crown glass and cylinder glass were advancements, but still required laborious hand-grinding and polishing to produce.The industrial revolution brought about steam-powered machines to improve on these functions. As the production of glass lites became possible, some of the rich began to replace the shutters on the “wind-eyes” in their homes with windows made of glass.
In 1688, a technique for the production of cast polished plate glass was developed.This made large vision areas possible rather than holding a bunch of small pieces of glass together with lead. By the mid-1800s the use of glass to enclose wall openings became commonplace. PPG started production in the U.S.A. in 1883.
Machine drawn cylinder sheet glass – the first drawn glass as opposed to blown or cast – was produced in the U.S. in 1903. The commercial production of vertically drawn flat sheet glass began in 1914. For the first time it was possible to create a continuous ribbon of reasonably good quality glass economically.
The most significant strides in the manufacture of glass were made by Alastair Pilkington in the 1950s when he conceived the idea of forming a horizontal ribbon of glass by floating the melted raw materials at high temperature over a bath of molten tin to create the high-quality float glass we are accustomed to today.
With this modicum of glass knowledge you should now be capable of impressing your friends and maybe even the occasional architect.
Frank Fulton is president of Fultech Fenestration Consulting. He has been in the industry for 30 years and can be reached via email at firstname.lastname@example.org.
Categories: You Bet Your Glass