Would you believe it if we told you that glass existed when the Egyptians were crafting mummies and building the famous pyramids? The earliest samples of glass actually date back to around 3,000 BCE, in the form of jewelry beads. But what exactly is glass? And what is it made from?
Glass is made up of common sand (Silicon Dioxide, SiO₂) that is melted and cooled to form a transparent solid. Other materials like soda ash, limestone, and cullet (recycled glass) are also added alongside sand to optimize the process and create different types of glass.
From our car windows to eyeglasses to the screens on our phones, glass has become a staple material in our lives. Its simplicity and versatility are probably what make it so popular. Plus, it’s inexpensive to produce and can be easily recycled. Let’s find out more about this fascinating material and how it’s made.
What Is Glass?
Glass is an amorphous solid, which means it doesn’t have a definite crystalline structure like regular solids. Instead, the atoms are arranged in a disordered way, giving them a non-directional structure. This is what makes glass transparent — there isn’t any light interference from the atomic structure.
The lack of crystal direction also makes the glass very brittle. It can shatter easily if hit or dropped because the atoms don’t have a set pattern to hold them together.
Another amazing property of glass is that it’s inert, meaning it doesn’t interact or react with other materials. That’s why you see it is used a lot in food storage containers and laboratory equipment.
Glass is also a completely recyclable product. It can be melted down and reformed into new glass products repeatedly without losing any of its quality.
What Materials Are Used to Make Glass?
The primary ingredient in glass is sand, or more precisely, silica. Silica is the sand that’s more than 95% silicon dioxide quartz crystal and has less than 0.6% iron oxide. It’s an abundant material found in almost every corner of the earth.
The silica is melted at high temperatures — roughly over 1,700ºC (3,090ºF). Then the liquid is either poured, blown, or drawn into shape and left to cool to form the solid product. However, this is just the most basic recipe for glass.
Certain materials can be added to the silica to give the glass different properties. For example, sodium carbonate (Na₂CO₃) is added to decrease the temperature required to melt the silica. The resulting glass is called soda-lime glass and is the most common type of glass used in everyday items like windows, drinking glasses, and food containers.
Boron trioxide (B₂O₃) is another common ingredient; it makes the glass more heat resistant. Iron oxide is used to give a green tint, and cobalt salt gives blue color. Lead oxide is used to produce sparkling, crystal-like glass. So there can be a lot of variety in the ingredients used to make different types of glass.
Is It Expensive to Make Glass?
From a material perspective, glass isn’t that expensive. The cost of the raw materials used to make glass is between 10% to 30% of the final product. But it’s quite energy-intensive to produce. The melting process requires a lot of heat, typically provided by natural gas or oil.
The handling and transportation of the glass product also add to the final cost. All of this makes the glass more expensive when compared to other materials such as, for example, plastic.
Plastic needs much less energy to melt and can be easily molded into different shapes. It weighs less than glass, so the shipping and handling costs are lower. So, overall, it’s cheaper to produce plastic than glass.
Can I Make Glass at Home?
You can make glass at home if you’ve got the right equipment. As we explained before, glass is made by melting silica sand at high temperatures (1,700ºC / 3,090ºF). So you’ll need a furnace that can get that hot.
Some people have tried using a charcoal barbeque grill, which may work but is not very safe. You’ll also need some tools to handle the molten glass, like a blowpipe or mold.
Once you’ve got all the materials and equipment, the rest is pretty straightforward. You just need to follow the steps below:
- Mix the silica sand, sodium ash, limestone, and crushed recycled glass in equal parts. Silica is extremely irritant if inhaled, so use a proper respirator (on Amazon) when handling it.
- If you want to add additional components like iron oxide or cobalt salts to give the glass color, mix them in now.
- Put the mixture into the furnace, make sure it’s appropriately vented, and turn up the heat.
- Once the material has melted and reached the correct temperature, homogenize the mixture by mixing it with the help of a rock tumbler or steel rods.
- Let the glass kiln cool down slowly. In industrial practice, this step is called annealing. There are various techniques to anneal glass, and each type of glass has its ideal cooling schedule.
- Prepare the mold or holder where you’ll pour the mixture. You’d need a mold release agent (on Amazon) to prevent the glass from sticking to it.
- Pour the mixture into the mold or holder and let it cool completely. If you’re not an experienced glassmaker, it’s best not to try to do blowing or shaping on your own.
- Once the mold has cooled down, you can remove the glass piece. The final product may crack or shatter into small pieces because of the rudimentary method. So don’t be discouraged if it doesn’t turn out perfectly!
Glassmaking isn’t exactly a DIY project for the novice. Unless you’re experienced in working with high temperatures and furnace-type equipment, we recommend leaving it to the professionals.