Glassmaking–the know-how to turn sand into glass–was discovered in only one place and time: Mesopotamia, some 4000 to 5000 years ago.[1] This is remarkable. Why? Because all the other basic materials technologies—pottery, weaving, working in stone, wood, then metals–were discovered one by one in every part of the ancient world, each in their own times. But true glass was only invented once. Its manufacture requires special conditions. These include sandy beaches, shrubs that thrive in salt water and incorporate the salt into their bodies, plentiful wood for fuel, and extremely hot furnaces.
The bronze-age cities of Mesopotamia were famous for their furnace technology. Abraham, ancestor of the Jewish people, came from Mesopotamia. When his descendants eventually reached the land we now call Israel they found the other conditions there which are needed for glass-making.
The Mediterranean coastline of the Galil provided sand of exceptionally pure, white quality. From this the tribes of Zebulun and Issachar who settled there could produce the “white,” i.e. clear, colorless glass so highly prized throughout the ancient Middle East. But good sand and super-hot furnaces (by ancient standards) aren’t enough. Even the hottest furnaces of antiquity, the famous furnaces of Ur Kasdim and Babylon, were not hot enough to melt sand.
Nevertheless, the glassmakers of the ancient Middle East found a way to do it. By mixing certain substances with the sand they could make sand melt at a much lower temperature, one that their furnaces could reach. The necessary substance, called a “flux,” was rich in sodium ions. The original flux may have been the ashes of saltwort and other plants that thrive in the very salty soil and marshes of the Galil. How flux works can be understood on two levels: the ultra-microscopic level of atoms, and the macroscopic level of universal forces.
Chemistry of Glassmaking
Sand is basically crushed quartz. It consists of two elements: silicon and oxygen. Each silicon atom sits in
The basic silicate unite. Silicon atom (gray) surrounded by four oxygen atoms (red)
the middle of a tetrahedron of four oxygen atoms. Each oxygen atom is shared by two silicon atoms. The tetrahedra can be arranged in chains, rings, or three-dimensional networks. The orderly arrangement creates the beauty of quartz crystals.
In the ultra-microscopic world of atoms, nothing stands still. Atoms constantly jiggle and bounce, stretching and twisting the bonds between them. Add heat and the jiggle and bounce, stretch and twist, further and faster. That’s how heat melts solids and turns them into vapor: the atoms literally shake themselves away. The stronger the bonds are between atoms, the more heat is needed to shake the bonds loose.
Those bonds between silicon and oxygen of sand are covalent, meaning they share electrons. In effect, the atoms actually get under each other’s skin!. Such bonds are very strong. That’s why sand needs extremely high temperatures to melt. However, mix in a little sodium-rich flux, and the sodium moves in on the oxygen. It disrupts the oxygen-silicon bonds.[2] On the atomic level, flux is a bond-breaker. Its chemical forces do the work that otherwise would require extra-high temperature. Flux has lowered the temperature needed to melt sand.
Disorder Rules!
But there’s more. Broken by heat and flux, the sand molecules are no longer arranged in orderly chains or networks. With more heat and plenty of sodium the disorder grows. The effect on temperature is what chemists call melting point depression. It works by harnessing one of nature’s most powerful driving forces: the drive to increasing disorder. Scientists refer to disorder as entropy. Any change in the physical world increases the total entropy of the universe. This is one way of stating the “Second Law of Thermodynamics.” It’s a “Law” that works everywhere, not just in the chemistry lab.
For example, you might think that hanging up your clothes neatly in your closet decreases overall disorder. And so it does—within your bedroom. But doing so you had to expend energy which you got from food. Food on your plate consisted of large, intricately structured molecules, which your digestive system broke into much smaller, simpler molecules, many more of them than in the original food. These smaller molecules end up mixed into the air and water of the environment as you excrete waste. The final result is that the universe’s total disorder, its entropy, increases. The entropy of glass is greater than that of solid quartz and the entropy of a speck of glass is greater than that of a same-sized grain of sand.
Glass-making uses heat to break up the orderly silicate structure of sand crystal
Perhaps this drive to increase entropy goes back to the condition of the universe before the world was created. Torah tells us: “The world was tohu v’vohu…”[3] The Ramban explains[4] that tohu is the original substance that G-d created. Tohu has no form. It’s not a solid or a gas, not motion, not heat, not dark, not light, not dead, not alive. Created from nothing, tohu is the first something. Hidden within tohu are all the possibilities to become anything at all. In that sense, it is the ultimate mixture. From tohu, G-d formed and made all of the distinct creations that now fill the physical world. Yet entropy drives all of creation to mix back together, to lose all identity and distinctions. For you are dust, and to dust you shall return.[5]
When the Jewish people accepted the Torah, they accepted the role of being a distinct people. Not only that; they accepted commandments (mitzvoth) to keep other distinctions. Separating meat from milk in the kosher diet, and linen from wool in kosher clothing, not mixing different types of seeds in our farms and gardens—these are just a few examples of commandments that organize the world into distinct categories. Why did G-d created a universe in which overall disorder always increases? Science can only tell us what happens, and how, never truly why. The hidden things belong to the L-rd our G-d, but the things that are revealed belong to us and to our children for ever…[6]
[1] Kurinsky, Samuel, The Glassmakers: An Odyssey of the Jews. New York: Hippocrene Books, 1991, p.31.
[2] Bray, Charles, Glass blowing, 2003, p. 58