Dr. Universe: How do people stain glass to make it all the colors it can be? – Emily, 10, Edmonds, WA
Ever since humans discovered they could use sand to make glass, they’ve been experimenting with it. They even learned how to control the colors.
My friend Dustin Regul is a stained glass artist and painter who teaches fine arts at Washington State University. He told me more about where glass gets its color.
“It’s actually metals that help change the color of the glass,” he said.
We can add these metals to glass in the form of a compound. A compound is a combination of one or more elements. For example, table salt is a compound made up of the elements sodium and chloride.
Yellow glass can be made using a compound called cadmium sulfide. Red glass can come from adding gold chloride. Manganese dioxide can make glass purple. Blue glass comes from adding the compound cobalt oxide.
Glassmakers add in compounds when they melt the sand. The temperature has to be just right for everything to work. They heat the sand to about 3,000 degrees Fahrenheit—that’s even hotter than lava. As the melted sand cools, it becomes glass.
It turns out, glass made from melted sand doesn’t always instantly become transparent. The glass sometimes has its own natural color.
“You can imagine really old glass bottles,” Regul said. “They kind of have that bluish or greenish tinge.”
Glassmakers also figured out that a compound called sodium nitrate could help clear up the glass.
Regul said glass is a pretty unusual material. It’s not a solid or a liquid. Scientists call it an amorphous solid, which means a state somewhere in the middle of those two states of matter. It’s also a very fragile material.
Regul must be very careful when he works on stained glass projects. Before he gets started, he makes a plan and draws out his design on paper.
Next, he cuts up the paper drawing into pieces. It’s a guide that will help him as he cuts pieces of glass into shapes with a special glass cutting tool. Finally, he uses copper tape to connect the pieces together and applies heat to seal it all up.
In medieval times, when stained glass first became really popular, people used a different technique. The glass pieces were held together with long strips of a bendy material made of lead. On each side of the lead strip was a little channel where the edge of glass could be tucked in. And like the technique Regul uses, adding heat to the strip helped keep the glass in place.
Humans can use these really small pieces of glass—in all sorts of colors—to form a bigger picture or story. Whether you are in the lab or the studio, it’s amazing what you can create and discover when you set your mind to it.
P.S. Be sure to check out the Ask Dr. Universe podcast on Spotify, iTunes, or at https://askdruniverse.buzzsprout.com/.
With help from my friends at Washington State University, we’re investigating tough and smart questions from curious kids around the world.