If you’ve ever tapped a screen to send a tweet, opted for the bottled soda because
it tastes better, or drooled over art glass in a gallery, then your life has been changed
for the better by the transparent yet durable combination of sand and simple chemicals we
call glass.
We visited McFadden Art Glass in Baltimore, MD to watch and learn how glassblowing is
done.
And along the way we learned about the chemistry of this ancient stuff.
For thousands of years, we’ve known how to turn ordinary sand and other common ingredients
into glass for purposes both decorative and functional.
The ancient Egyptians used bits of colored glass for decoration, but it was the Syrians
who figured out how to shape glass vessels by blowing air into them around the first
century BCE.
First things first--let’s talk about what glass actually is--sand.
That’s right.
The main ingredient in most glass is plain, normal sand.
Sand is made of silicon dioxide, aka silica, one of the most common minerals on earth.
At around 1700 degrees C this silica melts.
But 1700 degrees is really really hot, so we add soda to the silica.
No, not that stuff.
Soda is the common name for sodium carbonate, which lowers the melting point of silica to
a more manageable 850 degrees.
But that makes the silica water soluble.
And no one wants a glass of water that dissolves in your hand.
That’s why we add lime.
Nope, wrong again.
Lime in this case refers to calcium-containing stuff such as calcium carbonate, which solves
that pesky solubility problem and gives you glass that’s both durable and practical
to work with.
These guys in the studio leave that initial formulation to a factory and start with these
shapeless little pillows.
In part that means they don’t have to get their furnaces TOO too hot.
But they still have to melt the glass down into a blow-able form to create amazing shapes
and colors.
Soda lime silicate glass makes up most of the glass you’re likely to run across.
That basic recipe won’t change, but there are some small tweaks to the proportions that
can be made to change the glass’s properties like how much it expands when heated.
And there are all sorts of additives that can give glass useful properties.
Including boron oxide makes a borosilicate glass that is much more resistant to heat
and sudden changes in temperature, making it useful for both cookware and laboratory
glassware.
You can thank boron next time your pyrex casserole dish doesn’t shatter when you move it from
the oven to the fridge.
And the glass in your smartphone screen contains aluminum and potassium to make it strong enough
to stand up to drops, scratches, and really aggressive Snapchatting.
Now let’s get into some of those colors, which come from simply adding things to the
glass.
Glassblowers might buy crushed-up bits of glass with the color already incorporated,
like this stuff, but how the color gets there can affect both the price and the properties
of the finished product.
Oftentimes the source of color is the metals bunched up in the center of the periodic table
called the transition metals, incorporated into the molecular structure of the glass.
In their normal condition these metals have a reflective sheen, but oxidize them by removing
a few electrons and they often contribute bright colors.
Metals like iron, chromium, and even uranium can be used to color glass in shades of green,
for example, although we do not recommend making radioactive soda bottles.
The reverse process can also be applied.
When these oxidized metals are present in glass, heating them in a low-oxygen flame
can produce a spectacular effect.
This so-called fuel-rich flame starves the glass of oxygen so electrons aren’t gobbled
up, which is oxygen’s favorite activity.
Then electrons are left around to hit up the metals in the glass and revert them to their
shiny state, giving the glass a mirror-like quality.
Other ways metals can create colors is if they form nanoparticles that get swept up
in the glass itself.
Super tiny globs of say gold or cadmium selenide can cause red light to scatter around.
Carefully controlling the mix makes for a glass that looks like ruby.
Of course, glass blowers have to be careful with those colors -- did we mention GOLD?
That’s one expensive way to bring out the rainbow!
We watched them use a thin layer of colored glass with additional layers of clear glass
to create a translucent but vibrant effect.
Cinderella’s godmother might have turned a pumpkin into a carriage, but we’re happy
with turning sand into a pumpkin.
Many thanks to McFadden Art Glass in Baltimore for letting us film in their studio.
Have you ever tried glass blowing?
Tell us about it in the comments, and hit thumbs up and subscribe on the way down.
See ya next time!