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.
However glassmaking was first discovered, historians agree that it happened about 6,000 years ago. The story of glassmaking after that is one of continuous technological change: refining the recipe to create new types of glass, learning to shape it into new forms, and finding new and better uses for it.
GETTING INTO SHAPE
The first known methods used for shaping molten glass into objects were drawing and casting.
* Glass drawing. A metal hook is used to pull molten glass out of a tank while it is a very thick, red-hot liquid. In this state the glass can be drawn -much like taffy- into long, thin strands, which are allowed to harden into rods or are cut into decorative beads while still soft.
* Glass Casting. Molten glass is poured into a form and allowed to harden. The earliest glass molds were probably made out of sand.
These methods are believed to have been first used by Sumerians in ancient Mesopotamia (Iraq and Syria) more than 5,000 years ago. Glass beads and simple cast pieces dating to approximately 3,500 B.S. have been found in the region, and glassmaking instruction have even been discovered in ancient Sumerian texts. This new technology was passed around in trade routes to neighboring societies, and over the next 2,000 years, simple glassmaking spread across Mesopotamia and the Middle East.
CUP RUNNETH OVER
The next big leap for glassmaking was using it to make containers. Around 1500 B.C., Egyptian glassmakers discovered that they could dip solid cylinders of silica paste (made of crushed sand and water) into molten glass. They allowed the glass to harden and then broke the core out -thus making the first known glass containers. The method was improved by pouring molten glass over compacted sand forms, and later by another technique, known as glass pressing: molten glass was poured into a mold, and another mold was pressed down into it. (This is till how many bottles are made today, but the process is done mechanically.)
A huge improvement over wood or clay containers, glass was put to many uses: as bottles for perfumes, dyes, and cosmetics; or as containers for carrying and preserving food and beverages such as honey or wine.
At the time, Phoenicia was part of the Roman Empire. The Romans embraced the new technology and over the next several centuries spread it throughout their empire, including the Middle East, North Africa, and almost the whole of Europe. Glassblowing would remain the dominant way of making glass in these regions for the next 2,000 years.
The fall of the Roman Empire in the fifth century marked the beginning of the Dark Ages in Europe and a near-halt in the progress of glassmaking. But by the seventh century, new Muslim empires began to flourish in the Asia and Africa. Over the next several centuries, Arab artisans, especially those from Syria, became the world’s premiere glassmakers. They made huge advances in cutting, engraving, and coloring techniques, as well as inventing ways to paint, enamel, and gild glass. Intricately decorated, multicolored, gilded glass pieces from this era -especially vases in a wide variety of shapes- have been found in all parts of the Arab world. Even after dominance in the trade would shift back to Europe, European glassmakers were greatly influenced by the artistic and scientific advances of their Arab counterparts.
THE INDUSTRIAL REVOLUTION AND BEYOND
* In 1926 Corning developed the “399” or “Ribbon” machine to make light bulbs. It was soon capable of making 400,000 bulbs a day, more than five times the amount made by previous machines -which made light bulbs affordable for ordinary households.
* In 1959 Britain’s Alistair Pilkington invented the “float process” for making sheet glass. A sheet of molten glass is drawn from a tank, then floated over the surface of a tank of molten tin and allowed to cool. This results in the smooth, lustrous, and consistent finish that consumers now expect -and take for granted- in windows. Nearly all sheet glass made today uses the float process.
* In 1970 Corning developed a workable silica optical fiber, an idea that had been around for decades. Used mostly for data transmission, this breakthrough jump-started the “fiber-optic” age.