The History of Glass

ANCIENT GLASS

Glass has existed for millions of years. Whenever natural events involving super high temperatures -volcanic activity, lightning strikes, or the impact of meteorites- cause certain type of rocks to melt, fuse, and then cool rapidly, glass is formed. Fossil evidence shows that Stone Age humans used this natural glass to make tools, such as spearheads, and cutting instruments, as far back as 9,000 years ago. (Better dating techniques may eventually push that date back much further.) Obsidian, the shiny black glass formed when lava cools quickly (as when flowing into water), was widely used by ancient people for these purposes.

After thousands of years of using naturally-formed glass, humans finally discovered how to make it -probably by accident. The Roman historian Pliny wrote in A.D. 77 that Phoenician sailors places "stones of soda ash" into a fire (presumably to rest their posts on) on a sandy beach. They later found a "hard smooth stone" in the ashes. That's one possible scenario, given that sand, soda ash (sodium carbonate) , and heat are all ingredients for making glass. Another possibility is that potters inadvertently let some sand drift into their kilns, where it stuck to the wet clay, accidentally creating a hard, smooth glaze on their pottery when the baking was done.

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