John Kemper, age 8, of Indianapolis, Tnd., for his question:
How was glass discovered?
The discovery of glass making was described by the Roman writer Gaius Plinius Secundus ‑ bettor known to us 8's Pliny the Elder. Pliny lived from 23 to 79 A.D. and wrote, among many other things, the first encyclopedia. Pliny said that glass wes discovered by accident and tolls a believable story of how the happy accident occured.
The discoverers, according to Pliny, ware a crew of Phoenician sailors. The Phoenicians of early days were great traders and sailed their trading vessels from port to port around the known world. This particular crew decided to spend a night on land. They selected a stretch of sandy beach in Palestine. They probably cooked supper, then wrapped up in their blankets to sleep under the stars. At any rate, we know they made a camp fire.
This camp fire, says Pliny, was responsible for the discovery of glass. It was just a pile of driftwood on the beach. The sailors built it carefully, first arranging a base of stones for firebricks. The s:jna on the beach must have bean clean and white for, in order for the miracle to happen, the sand had to be high in silica content.
The firebricks also had to be of a special kind. The stores accidently chosen were patron rocks, marring high in sodium. They may have been patron granite or the mineral natrolite ‑may have boon present on the surface of the stones. This mineral, high in sodium, occurs in a colorless crust on certain racks.
The sailor s camp fire added heat to the minerals bearing silica and sodium. And, when fused, these elements formed a primitive glass. In the morning the campers found gobs of this mess in the ashes. This, says Pliny, is how glass was discovered.
Pliny's story may be true. But this certainly was not the first time Mass zvns discovered. Glass was nado and used by the Egyptians thousands of years before this happy accident. Glass objects were buried in the Pharaohs tombs as long as five or six thousand years ago.
We do not know how the Egyptians discovered glass. Perhaps they, too, found it by accident in the ashes of beach fire. At first they used it only as a glaze. Beads of clay were dipped into the hot, sticky glass. When cool and dry, this gave them a hard, glossy coating.
Later the Egyptians learned to make small beads entirely of glass. They were able to color their Class green and red. The green colors came from a trace of iron mixed with the sandy silica. The rods came from a trace of copper. To the Egyptians, glass making was a fine art. The job was difficult because it required a lot of heat and our modern fuels were unknown. The glass beads of Egypt were as valuable as rea1 emeralds and rubies.
No ono knows how, but someone discovered that lime improves the quality of gless. Limestone was added to the send and soda ingredients in the furnace. Nowadays, each type of glass calls for a different recipe. But the basic ingredients are still the same as they were 6,000 years ago, And they are still fused together under grout heat.