I asked the girls to write me up a short report on one of a few different questions, and one of them was how glass was made. Victoria chose that one and here’s her report (with photos she found and included). In case you were wondering! 🙂
Glass making was invented by people around 3000 BC. Before that, glass was formed by nature. Sand being struck by lightning makes thin, long tubes of glass, while volcanoes make chunks of black glass called Obsidian. The first glass was probably used as a glaze for pottery. Glass is now made by melting sand, silica and lime and fusing it together at very high temperatures. The silica/lime/sand mixture is heated to 2000-2500 degrees Fahrenheit, sometimes for up to 24 hours. At this point, he glass is reddish orange and is like a thick liquid. Adding other substances during the process changes how clear it is, how well it insulates and more. Bits of recycled glass (called cullet) of the same type are usually added to reduce the temperature needed to work it. Colors are made by adding chemicals. Gold chloride makes a beautiful ruby red, and cobalt oxide makes a deep blue. Blown glass is made by putting a piece of glass on a long, thin metal tube and heating it in an oven. When it’s hot enough you blow into the tube and it makes the glass bubble.
blown glass window