An In-Depth Guide to Glass: from Sand to See-Through

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Glass just might be the most versatile material that humankind has ever discovered. With numerous different types of glass, it’s no wonder that there are thousands of unique uses created from these incredible resources. 
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Glass just might be the most versatile material that humankind has ever discovered. With numerous different types of glass, it’s no wonder that there are thousands of unique uses created from these incredible resources. 

A vast majority of people are under the impression that glass is a more expensive material than plastic because of its weight. However, this is a common misconception that has been perpetuated by the plastic industry for decades. In fact, glass is longer lasting than plastics and can be recycled indefinitely, proving that this material is far superior to what we’ve been told. 

Let’s take a look at what exactly glass is and how it’s made! 

A Brief History of Glass


The glass production process may seem complex, but it’s actually quite simple and has been around for over a million years. The first records of glass were found using volcanic glass, or obsidian (nature-made glass), used as arrowheads, knives, money, or jewelry. 

Glass blowing’s rich history dates back to the 1st century BC when the oldest known glassblowers began to harness the trade in Syria and Palestine. Since then, glass blowing and glass manufacturing has taken off, quickly becoming one of the most valuable building materials for a wide variety of uses. 

What is Glass Made of?


Glass starts off as a type of sand, sort of like what we find on our favorite beaches. This fine, almost powder-like substance consists of a mixture of glass-specific sand and silica, called silica sand. 

Glass containers are primarily all made of a base mixture of silica, limestone, and soda-ash, melted down into a viscous liquid. When the base is melted down, it is sometimes treated with additional materials to alter the functionality after cooling. These different mixtures create unique properties, so the glass is able to best serve a certain purpose. 

There are different types of glass ingredients other than this base, but 90%1 of all manufactured glass starts with those three. Of course, with different additives come different uses, like making the glass stronger, more heat resistant, or adding colors.

It’s the same for different colors of glass products, each shade is created differently, with additives that bring out vibrant colors. The majority of these additives are different types of oxides, for example, manganese dioxide for clear or light purple glass, chromium oxide for green, and so on. 

Oftentimes color is also derived from different metal additives, like iron or nickel. However, there are other important components added that can alter the color, such as calcium, coal, and different phosphates. Each shade of glass cannot be combined in the process because the additives will have chemical reactions with each other.

Once the specific ingredients are combined, the mixture is heated in a high-temperature oven until it reaches over 3000 degrees! The temperature is so extreme that the silica sand is melted into a liquid, which will inevitably harden into the glass we use every day. 

There are a few different procedures that could be used to shape the glass into different products, it could be blown by hand or by machine, poured into a mold, or what is called float glass.

Blown Glass


Blown glass is typically reserved for art or customized pieces, but some machines also function to blow glass in a larger production process. 

Hand-blown ornate designs are more intricate, and require a human touch, making them more desirable and slightly less common than regularly manufactured glass. In this process, the “gob” or a large liquid sphere of glass, is attached to the end of a metal rod called a blowpipe, the glassblower then uses the pipe like a straw to blow air into the glass. 

After the glass expands with the air, it is manipulated using heat-resistant tools such as tweezers. The glass is often reheated and re-blown until the proper shape is achieved, adding in other colored glass to adjust the design. 

The final product is then set by placing it in a kiln, typically regulated at around 900 degrees. This allows the glass to slowly cool, preventing damage and ensuring its quality.

Glass Molds


Molds are a more common form of glass manufacturing and use similar methods as blowing. Professional glassblowers will occasionally use molds for their products, but not as frequently as blown glass. While both blowing and molded glass can be made by machine, it is more commonplace to see molds produced this way. 

In this process, a gob is cut by a timed blade to be moved to the formation machine. 

Next, the machine uses the press and blow method to shape the glass in a specific mold, using gravity and blowing hot air into the gob simultaneously. This forces the glass into the corners of the mold.

The mold is then removed and the glass is reheated at a lower temperature. Lowering the temperature means the glass is gradually cooled to treat and finalize the product. 

Float Glass


The last option for processing glass is what is called the float glass method. This approach is used primarily for larger slabs of glass such as windows or building materials. Using the float glass process creates a distortion-free slab that can be cut into smaller pieces, perfect for mass production units. 

The molten glass is laid out on a large slab of tin, a material that repels glass—think of oil and water, the same idea applies here. The glass is floating above the tin and spread evenly across the surface, during which the temperature is regulated until it can be slowly cooled over time. 

All glass takes time to cool, which is why they are such stable materials. Compared to other methods, floating is the youngest process in glassmaking, as it was discovered just 70 years ago in the 1950s! It’s pretty remarkable that millions of years after the discovery of glass, we are still learning new ways to produce this adaptable resource.

The Potential of Glass

While there are different types of processes to produce glass, the product remains the same: an inorganic, solid material, impervious to natural elements. This final product can be repurposed and recycled indefinitely, creating new uses with every new product. So when we break glass, it is not a lost product, but instead the potential for something brand new.

Glass is an exciting material because with glass comes endless possibilities. The curbside recycling system only recycles about 24%2 of glass… and glass that does not get recycled will stay in a landfill for one million years! 

Glass should always be recycled because these materials are invaluable resources, and the Lasso is doing just that! 

Stay in the loop ♻️ for recycling knowledge simplified & to get notified when the Lasso will launch near you!

#recyclingrevolution

Sources:
1.
https://www.thomasnet.com/articles/plant-facility-equipment/soda-lime-glass/
2.
https://www.gpi.org/glass-recycling-facts

Abigail Holt // 12 April 2022

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