Glass History
This Journal will cover glass, and to learn more about glass we are going to take a quick look at some Glass History. Early man likely first encountered glass in two locations. One was in the desert or along ocean shores where deposits of sand could be struck by lightning. The heat from a lightning strike fused the sand into a melted glass deposit that the Romans called Fulgurite, from the latin word fulgur, which means lightning.
Volcanoes also created a form of black glass called Obsidian when sand was melted by the hot gases during eruptions. Obsidian was valued in Stone Age cultures because it could be shaped to produce sharp blades or arrowheads.
The problems with early glass making were primarily due to the high melting temperature required to melt silica (3600F), but this was solved by accident along the shores of the Mediterranean Sea.

The Roman historian Pliny the Elder, records a story of Phoenician traders who first stumbled upon the glass manufacturing techniques that are still used today. They were hauling saltpeter that was used for Mummies, like that of Rameses II, whose body was left for seventy days in saltpeter, thus embalming it.
According to Pliny, on a long-forgotten evening after landing on the coast of Palestine, the Phoenicians set about the task of preparing their evening meal. Being unable to find proper rocks on which to set their pots, they obtained some cakes of saltpeter from their ship's cargo and placed their cooking vessels on them before lighting a fire. The heat from the flames caused the saltpeter and quartz sand on the shore to melt. These combined into streams of an unknown clear fluid, which hardened into a translucent substance now known as glass.
Later - other materials like sodium carbonate were tried and mixed with silica sand to drop the melting temperature of glass to a more manageable 2192 F, which made glass making a far more manageable process.

But there was still a problem – the sodium carbonate made the glass water soluble. Then - lime (Calcium Carbonate), a material used for concrete in building materials, was added to the glass, and this made glass usable. This allowed glass making to spread throughout the Middle East.
This basic recipe of Silica + Sodium Carbonate (called ‘Soda’) + Calcium Carbonate (‘Lime’) is still with us today, and 90% of the glass in use is called ‘Soda-Lime’ glass.
The next breakthrough: Tempered Glass

The story of tempered glass can be traced back to the middle of 17 century when there was a prince named Rupert in Rhein who performed a fascinating demonstration. The prince put a molten drop of liquid glass into icy water, which then was transformed into a very hard droplet of solid glass. This high-strength piece of glass had a long tail that looks like a tadpole.
These glass teardrops, shaped with a long and curved tail, were known as Prince Rupert's Drops.
One of them could withstand a blow from a hammer on the rounded end of the droplet without breaking. Or it can be pressed with up to 20 tons of force, and even shooting it with a gun won’t do it a lot of damage.
To break it, however, you only need to tap its tail, which will cause the entire object to disintegrate explosively into powder when the tail end is even slightly damaged.
Although Prince Rupert did not discover the drops, he played a role in glass history by bringing them to Britain in 1660. He gave them to King Charles II, who in turn delivered them in 1661 to the Royal Society (which had been created the previous year) for scientific study.

Further glass hardening experiments over the years led to the process of tempering, which is the rapid cooling of glass. The glass material itself does not change after tempering, but the tempering process makes the glass about four times stronger than “ordinary” glass.

Tempered glass is used for lenses in Solas Ray LED fixtures certified by UL 844 for Hazardous Locations.
Bill Nagengast, Lighting Engineer
Solas Ray Lighting
Holds over 20 patents in the lighting industry.
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