SHREWSBURY, Massachusetts – There are many strange and mysterious things in the world such as UFOs, sea monsters, ghostly apparitions, etc., but one of the greatest enigmas is a commonplace item found virtually everywhere and constantly used by everyone. You may not realize it but the baffling item of which I speak is known to one and all simply as glass. That’s right, glass, the thing that’s made into windows, doors, mirrors, eye spectacles, drinking utensils, dishes, bowls, bottles, jars, salt and pepper shakers, lamps, light bulbs, table tops, vases, picture frames, knick-knacks, display cases, watch crystals, etchings, statuettes, jewelry, musical instruments, and insulation.
What’s so unusual about glass? I’ll tell you. First of all this most fragile and brittle of materials isn’t a solid though it’s one of the easiest things to break. Yes, it’s actually classified as a “super-cooled liquid” and you can look it up if you don’t believe me. How is that feasible you ask? Well most materials exist in one of three possible states either as a gas, a liquid, or a solid which they change into at very specific temperatures. As an example, we all know that water becomes a solid (freezes) at 32 degrees Fahrenheit and converts to a gas (boils) at 212 degrees Fahrenheit. At room temperature, some substances like copper are naturally solid, some like mercury are liquid, while some like hydrogen are a gas but virtually all switch from one state to another immediately when reaching their precise temperature… it’s not a slow process.
But not glass. Molten glass, hundreds of degrees hot, gets thicker and thicker as it cools until it can no longer flow or be bent though it’s technically still a liquid. And as illogical as this sounds, stained glass windows that are hundreds of years old have been found to be thicker at their bottoms than at their tops, providing evidence to the above.
But glass’s uniqueness doesn’t stop there, for what we think of as clear glass really isn’t clear at all since manufacturers employ additives to the mix depending upon its intended use. Crystal stemware actually contains lead for durability as well as giving it sparkle, and window panes, believe it or not, contain iron to improve their transparency. That’s why sheets of window glass have green edges, caused by the way the iron content refracts light.
Moving on and seemingly contrary to all reason, the glass used in solar panels has a smoky appearance yet is far more efficient in allowing the penetration of light than ordinary window panes because the iron has been eliminated. If you ever have the occasion to see the edges of solar panel glass, they’re gray rather than green.
So for what it’s worth, glass is a most unusual substance and should be looked upon with the awe and respect it deserves. Its chemical composition is just not as transparently clear as one would think.