As you may have previously read, my recent trip to the Corning Museum of Glass has left me pondering the physics of glass. If you have never been there before, the place is really neat! The museum is laid out with tons of interactive exhibits, as well as opportunities to hear presentations about the science of glass from people at the museum. You also have the opportunity to create your own glass creation... which is what I will be discussing in this blog post!
When I went, I made a glass flower: this includes a curly, solid glass stem with petals which branch out from that stem. However, it was glass forming, not glass blowing. The glass maker started off by gathering a lump of hot glass onto a rod, and let me roll the rod back and forth in order to distribute the glass into a spherical, smooth lump. Why does glass so easy do this? Glass is a unique solid because instead of having a rigid, crystalline structure, the molecules are able to slide past each other, allowing it to "flow" yet stay solid. These molecules are easily formed, through working and forming, into structures including my flower.
After I formed the lump, I then used a paddle to flatten the top of the lump, and began to roll the rod while pulling each petal out. As I time went on, it became more and more difficult to pull the petals out. This was due to the cooling of the glass. Heat energy was escaping the glass into the atmosphere, and as the heat energy left, the molecules experienced less motion. Although glass is different than other solids in the fact that it "flows", this loss of energy caused the particles to become more stationary, and therefore more difficult to move their structure.
After forming the stem, the glass maker placed a score mark on the glass, and giving the rod a tap, the flower broke smoothly from the rod; this was due to the stress on the glass, as I explained in my previous blog post. Since the score placed a lot of stress on one concentrated area of the glass, the glass easily separated with stimuli at that point.
The flower was then placed into a kiln to cool overnight. Why a kiln?, you might think. Going back to my previous post, it is rather simple: the glass needs to cool evenly in order to prevent excessive amounts of stress, and gradually cooling the glass from its initial temperature in a controlled setting is the best way to do so. The glass maker showed what could happen if the glass wasn't cooled in the kiln by heating a piece of glass and putting it directly in cold water. The glass shattered because the rapid temperature change caused rapid tension on the glass, putting it under pressure it could not withstand.
After my trip to the museum, I was glad to have a piece of work I could bring home with me! (Or rather, have mailed home!). Until next time, Fizzix Community, until next time.