Discover Glass is a series of activities created by PGC teaching artist Valerie Herrero, who has developed a socially distant community art program in her own artist practice. Discover Glass explores the science of glass and the process of making and using it. It makes connections between glass art and everyday glass designs one might have in their own house. The program offers kids and families the opportunity to work together, make discoveries, and learn about glass through different fun activities and creative challenges to complete from home with materials they already have on hand.
Glass Scavenger Hunt
Glass is all around us, but how long has it been there?
It is generally believed that glassmaking was discovered 4,000 years ago, or more, in Mesopotamia. There are several stories that may explain how glass making developed. One recounts Phoenician sailors who landed on the shores near Ptolemais (in modern-day Israel) and made a fire on which to cook a meal. The fire melted the beach sand into a liquid stream that later cooled and hardened into glass.
Another more likely scenario is that glass developed over a long period of time from experiments with a mixture of silica-sand or ground quartz pebbles - and an alkali. It is even possible that early glassmaking was influenced by other high heat industries such as ceramics and metalworking.
These stories give us some insight into the history of glass, however, the exact origin of glassmaking largely remains a mystery and no one knows for sure...
You can learn more about the origins of glassmaking by checking out more information from our friends at Corning Museum of Glass.
Such mystery is an even better reason for us to explore the glass that is all around us every day!
Home is the perfect place to discover glass in our everyday lives. Take a moment to take yourself on a scavenger hunt in your home.
Try This AT HOME
Here is what you will need for this scavenger hunt:
- Paper
- Pencil or writing utensil
- Close looking eyes
- A sense of scavenger hunt adventure
What to do:
- Make a list of all the things you find in your home made out of glass. What sort of things are you finding? What do these glass objects look like?
- Sketch the items you are finding. Drawing is a great way to get a closer look!
- Try categorizing them into groups with similarities and differences? Do these objects have anything in common?
Additional scavenger hunt: What more can you discover at home? What are the objects you use every day made out of?
Share Your Scavenger Hunt
Let us know what you have found! Post a photo of your scavenger hunt and some of your glass discoveries! Tag us on Instagram, Facebook, or Twitter and we might share your creation.
glass cookbook: What is Glass Made of?
Glass can be found everywhere! In the windows of our home, in the glasses in our kitchen cabinets, and even in our pockets. But what is it before it becomes all of those things? Can I make it?
Join us as we cook up some glass following this “glass recipe”.
Makes about 2 tons of glass. Serves everyone.
Prep time: 1-2 hours Cook time: 18 hours Cooling time: 10-40 hours
Ingredients of glass:
- 1500 lbs. Pure Silica Sand (SiO₂)
- 550 lbs. Soda Ash (Sodium Carbonate) (Na2CO3)
- 150 lbs. Limestone
- 65 lbs. Sodium Nitrate (NaNO3)
- 1 lb. Feldspar
- 1 lb. Lithium Carbonate (Li2CO3)
- 1 lb. ZInc Oxide (ZnO)
- 1 lb. Barium Carbonate (BaCO3)
- 1 lb. Fluorspar (CaF2)
- 1 lb. Antimony oxide (Sb2O3)
- 1 lb. Erbium (Er)
How to Prepare:
- Step 1. Put on a respirator! These chemicals are dusty and can get into your lungs.
- Step 2. Combine all ingredients using a large mixer.
- Step 3. Heat about 100 lbs. of the mixture in a gas (or electric) furnace at 2,400°F.
- Step 4. Allow to heat for about 1 hour at 2,400°F.
- Step 5. Repeat steps 3 and 4 until your furnace is full. Continue heating at 2,400°F for 9 hours.
- Step 6. Reduce heat to a light simmer, about 1,950°F, for 9 hours.
- Step 7a. If using glass for blowing, increase heat to 2,100°F and use immediately.
- Step 7b. If using glass for sheets or plate glass, ladle glass out of the furnace and smash flat.
- Step 8. Once finished with your masterpiece, place into an oven at 920°F.
- Step 9. Slowly cool for 10 hours.
- Step 10. Voilà! Remove items from the oven and use!
Variation: Fulgurites
Replace your heat with lightning! Fulgurites are forms that are created when lightning discharges into the ground and its high heat causes sand, soil, and organic debris to fuse and/or vitrify.
Ingredients List:
- Large area of sand such as a beach, desert or dune
- Lighting Storm
- Metal Stick (optional)
- Luck
How to Prepare:
Option 1
- Drive metal stake into ground
- Wait for storm
- Get lucky and have the lighting hit the rod.
- Carefully remove Fulgurite from the ground
Option 2
- Have lighting strike the beach, desert or dune.
- Get lucky and find it the next day!
Try This AT HOME
Create your own unique recipe for glass!
Here is what you will need for this imaginary recipe:
- Paper
- Pencil or writing utensil
- Your imagination
Using the ingredients of glass as a starting point, add your own unique ingredients and create an imaginary recipe for glass! You can either write, draw or write and draw your recipe!
- What could you add to make your glass sparkle?
- What could you add to make your glass smell sweet or stinky?
- What might you add to give your glass magical powers?
- What other variations of glass recipes can you create? What other recipes can you invent?
Share Your Cookbook
Let us know what you have cooked up! Post a photo of your cookbook! Tag us on Instagram, Facebook, or Twitter and we might share your creation.
Colors and Metals: What gives glass its color?
Have you ever wondered why some glass is clear while some is blue, or green, or even striped with yellow? Colored glass can be found in stained glass windows, in everyday glasses, cups and plates, and in the incredible artworks made by glass artists around the world.
But how does it work?
Color is an important ingredient of glass and like the other ingredients of glass - color also comes from the Earth! Minerals and metal oxides are added to molten glass. The ions in the metal absorb different wavelengths of light which then gives glass its spectrum of color.
In the early days of glass production color was largely a result of the natural impurities found in glass. For example, 'black bottle glass' was a dark brown or green glass, first produced in 17th Century England. This glass was dark due to the effects of the iron impurities in the sand used to make the glass and the sulfur from the smoke of the burning coal used to melt the glass. Different metals result in different colors and today color is added intentionally to produce all the colors of glass that we see.
The world of color is truly its own universe! Learn more about color in glass here:
Corning Museum of Glass
Compound Interest
Fun Facts:
- Did you know some glass can glow in the dark!? Uranium glass was invented in the 1830s and is made using uranium oxide.
- Clear glass is made by adding a decolorizer like Manganese dioxide which precipitates out impurities such as iron and sulfur compounds.
Try This AT HOME
Here is what you will need for your collection:
- Paper
- Pencil or writing utensil
- Close-looking eyes
- Some color! Like crayons, markers, paints, colored paper, or whatever you have!
What to do:
- Take a close look at all the colors around you! What colors are in your home or in your yard?
- “Collect” the colors you see to create your own color collection or home color palette like examples below or find your own unique way to collect colors by creating your own chart or spectrum.
- Try labeling your colors with the corresponding metal oxides from the glass color chart above.
- Find interesting ways to organize your colors—by object, similarities, or moods!
- Design your own glass artwork using the colors on your color palette! Sketch your design and add in your colors!
Share Your Color Palette and Drawings
Post a photo of your color palette and drawings! Tag us on Instagram, Facebook, or Twitter and we might share your creation.
Properties of Glass: Transparency vs. Opacity
Part 1: Transparency versus Opacity
It may be easy to forget about all of the uses of glass in everyday life because of one of its most important features: It’s transparency! Glass is used for things like windows, eyeglasses, picture frames, lenses, and test tubes because it is important to see the items on the other side of the glass.
Glass is a transparent material which means it lets light pass through it and allows us to have a clear view of the objects on the other side. Check out the windows in your home. Notice how you can see through them, almost as if there wasn’t a completely solid material in front of you. Now Imagine if your windows were not transparent, like the walls in your house. You wouldn’t be able to see outside or have light shine in to your house.
Materials that you cannot see through and don’t allow any light to pass through, like the walls in your house are called opaque. Sometimes materials might allow some light to pass through and not allow you to see on the other side. Try holding up a piece of paper toward a light. Notice the light shines through the paper, but you cannot see things clearly on the others side. This is called translucent.
Sometimes windows are made of translucent glass to allow light to shine through but allows for more privacy. Can you think of any reasons or places you would use or find transparent glass? Translucent glass? Opaque glass?
If you want to check out HOW glass is transparent watch this video.
TRY THIS AT HOME
Here is what you will need for your collage:
- Paper
- Glue
- Scissors
- Various materials from around your house like paper, aluminum foil, magazines, wax paper, plastic wrap, tissue paper, construction paper etc.
What to do:
- Find some household materials with different translucencies- such as paper, wax paper, parchment paper, recycled cereal boxes, plastic wrap, and/or aluminum foil.
- Try holding your various materials up to a light or to a window. Make notes of what you can see through and what you cannot.
- Use these materials to create your own composition/collage using various translucencies.
Share Your Collage
Post a photo of your collage! Tag us on Instagram, Facebook, or Twitter and we might share your creation.
Properties of Glass: state of matter
Part 2: state of matter
Glass is unique matter! We might think of glass as being a hard solid—but that isn’t the whole truth.
Glass is technically an amorphous solid--neither a liquid nor a solid, but sharing the qualities of both states of matter. It is formed by heating a mixture of dry materials to a liquid-like state. These ingredients are then cooled quick enough to prevent a regular crystalline (solid) structure. As it cools, the atoms become locked in their disordered liquid like state never forming the perfect crystalline arrangement of solid matter.
Check out the images (above) and descriptions below from our friends at the Corning Museum of Glass.
Gaseous state: individual molecules separated from one another by relatively great distances and moving in a chaotic fashion. No interaction between molecules except for collisions with one another.
Liquid state: molecules are held close by attractive forces, but are not held rigidly in position. They move about, changing from one disordered state to another.
Crystalline state: strong attractive forces hold molecules rigidly in position. Each molecule occupies a definite position, in a perfectly ordered three-dimensional lattice.
QUARTZ (A SOLID) VS. GLASS STRUCTURE (IN THE GLASSY STATE)
Glasses have the mechanical rigidity of crystals, but the random disordered arrangement of molecules that characterizes liquids.
How does it work?
Molten (liquid-like) glass is stored in a big bowl in a furnace to keep it hot and liquid-like. The furnace has to stay around 2100°F (That’s SUPER hot!) to keep the glass in this state. In order to work the glass, either a steel rod called a punty rod or a large steel straw called a blow pipe are used to “gather” or get glass out of the furnace.
Watch this video to see how glassblowers gather glass out of a furnace.
When glass is in its molten state, it is hot and drippy like lava with a consistency like honey. Glassblowers must constantly keep their punty rod or blow pipe turning, using centripetal force to keep the glass from going all over the floor! Once glass is removed from its 2100°F home, it immediately starts to cool rapidly. If the glass isn’t reheated, it will quickly freeze up and become solid-like.
Our friends at the Chrysler Museum of Art Glass Studio do fun glass performances on the Third Thursday of every month. Watch this playful demonstration of drippy and malleable hot glass.
(This performance was created by Gayle Forman, a graduate of the Pittsburgh Glass Center’s SiO2 Teen Program.)
TRY THIS AT HOME
Activity: Gathering “glass”: Honey Toast
Here is what you will need for your honey toast:
- Some kind of rod like a straw, a chopstick, end of a mixing spoon, or a honey dipper
- Honey (make sure it’s still a liquid and not solidified)
- Small cup
- Toast
What to do:
- Make some toast (with help from a grown up if necessary).
- Put some honey (your molten glass) in to a small cup (your furnace)
- Use the end of your rod to gather a bit of honey from your cup.
- Try to keep the honey on your rod by turning it constantly – centripetal force helps you to keep the honey on your rod as you turn.
- Stop turning and drizzle the honey on your toast – this is what happens to glass when you stop turning, gravity pulls it down.
- When you’re finished, enjoy your toast!
For an additional fun challenge: Try using a utensil with an irregular tip like a butter knife. Do you need to do anything different to keep the honey from dripping off? (Not everything made in glass is round. Sometimes it’s easier for sculptors to flip their rods back and forth instead of turning to keep the glass from falling off.)
Watch Bill from the Corning Museum gather honey.
Share Your Toast
Post a photo of your honey toast! Tag us on Instagram, Facebook, or Twitter and we might share your creation.
Properties of Glass: temperature and stress
Part 3: temperature and stress
In Properties of Glass Part 2—we discussed how malleable hot glass can be and how quickly it cools when it’s removed from the furnace.
Glass is kept in furnaces at 2100°F for glassmakers to work with. In order to keep the hot glass malleable (or capable of being shaped), it needs to be constantly reheated so it remains within a working temperature.
Meet PGC’s Roary the Reheating Chamber! 
Roary is one of our many reheating chambers, also known as a glory hole. The glory hole is a metal drum turned on its side, lined with a high-temperature refractory brick and material. It is powered by natural gas and resides at around 2150˚F at working temperature.
Glory holes are only turned on as needed, but need about half an hour to warm up before working.
The longer glass is out of the furnace, the longer it takes to reheat. If it gets too “cold," the glass becomes stressed and it could crack and break like this demonstration.
So how do we keep cooled glass from breaking?
Glass must be properly annealed, or cooled slowly, to remove any stress in the glass. As glass pieces are finished, they are loaded into an oven called an annealer. Our annealers sit at 930° F and are cooled slowly on a computerized program. Inadequately annealed glass is likely to crack or shatter spontaneously.
A polariscope is a special tool that can be used to see whether glass has been properly annealed or still contains stress. Look at the two images (above) of two cooled glass objects under a polariscope.
Notice how colorful the image on the left is? This glass has not been properly annealed. The colorful area is showing the internal stress of the glass. The glass to its right has been properly annealed and is not showing any signs of stress.
This image on the right is looking at a stressed glass work under PGC’s polariscope. Although the stressed glass looks beautiful and colorful under the polariscope, the object is likely to break!
For more stressed glass fun check out this example of a Prince Rupert’s Drop.
TRY THIS AT HOME
Here is what you will need:
- Looking Eyes
- Paper
- Pencil or other drawing tool
- Color! Crayons, colored pencils, markers, tissue paper, construction paper; whatever you have
What to do:
- Find one of your favorite glass items in your house to sketch. You may also want to come up with your own imaginary glass object!
- Sketch your object.
- Pretend your glass has not been properly annealed. Color in what it might look like under a polariscope. You can use colored pencils, crayons, markers, or even collage materials!
Additional Challenge: Try creating a stressed glass matching game! Choose as many glass objects as you can find. Sketch each object on a small square of paper. Then sketch and color the same objects again – pretending they are stressed on more pieces of paper. Flip them over and try to find all the matches!
Share Your Artwork
Post a photo of your stressed glass artwork! Tag us on Instagram, Facebook, or Twitter and we might share your creation.