Natural Glass & Manufactured Glass: How is Glass Made?



Glass truly is a unique material, one that’s almost as flexible practically as it’s flexible physically. A chemically neutral material that can be created in a host of different ways, glass has been used throughout human history since before 2,000BC, originating in Mesopotamia, and has only been utilised more and more throughout the millennia.

Despite being so common in our modern age, glass can be found in nature in a variety of different forms. Glass may be mostly man-made nowadays but the natural beauty and strength of natural glass are undeniable. Despite all of this, it’s hard to pin down just how strong glass is, especially as scientists often state that glass is more of a state of matter rather than being a single type of material.

From the polished sheen of natural obsidian to the enchanting finish of antique mirror glass, we take a look at how the process of crafting glass has changed and evolved over the last few millennia.

Natural Glass: Obsidian 

Perhaps the best-known type of natural glass, obsidian is created when molten rock is quickly cooled by suddenly encountering water or air. Many will recognise obsidian by its telltale black sheen, though on rare occasions it can have snowflake-like specks on its surface or even an iridescent, rainbow-like sheen.

Obsidian occurs naturally all throughout the world, essentially wherever volcanic erupts occur. Obsidian can be found everywhere from Argentina to the United States, often whilst hiking near volcanic areas, though some surprising areas include the likes of Japan and Scotland. The natural beauty of this glass makes it an appealing ornament, though it is not the only example of natural glass.

Natural Glass: Lightning Strikes & Meteorites

The process of creating glass is essentially superheating sand, which is how seemingly random pieces of glass can be found in nature. Two of these types of natural glass are Tektites & Libyan Desert Glass, which is formed by the intense heat & force created from meteorite impacts, as well as Fulgurites, which are the result of lightning striking the sand.

Even more bizarre are the biological examples of glass. It’s extremely rare, but there are species of marine life, including sea sponges and microscopic algae, that have skeletons that are technically natural glass, being formed from siliceous.

Manufactured Glass: Glassblowing Tools

Crafting glass takes many different forms, though many of these methods generally require the same tools. 

The main tool for any method is the blowpipe; the heart of any glassblower’s toolset. This steel pipe gathers glass on one end while the glassblower blows air from the other end, filling the still malleable glass with air. Another essential tool is the marver, a steel slab that’s used to roll the glass. These tools were traditionally made of marble, yet due to glassblowing becoming more and more common, the steel alternative was adapted as a cheaper option.

Next is a fairly basic yet essential inclusion, the simple yet aptly named Bench. This is simply a glassblower’s workstation and, like any craftsman’s work station it has a place to sit and spots to safely store additional tools. What sets it apart from conventional craftsman’s work stations is the inclusion of two rails that are used to roll pipes when working.

Manufactured Glass: Container Glass

One of the hallmarks of entering the modern era of glassblowing was when the process could become automated, which is exactly what the Blow & Blow Method and the Press & Blow Method entailed. Developed in the latter half of the 19th century, these methods allowed the glassblowing process to become machine run. 

Both processes began the exact same way, mixing together all of the raw materials (including sand, limestone and any chemicals used for colouring purposes when crafting coloured glass) before being heated into ‘gobs’ of glass. These gobs would then be handled differently depending on the method practised. Both would compact the gob into a mould, with the likes of plungers and presses moulding the gob into distinct shapes like bottles and jars. 

Bottles would commonly be created via the blow & blow method, where the neck is formed by placing the gob into a mould and then blank is blown into it. The likes of jars are made via the press & blow method, which is formed by using a distinct mould that’s pressed via a plunger before being transferred to a special blow mould.

Manufactured Glass: The Westlake Process, Free Blowing & Mould Blowing

This process is essentially the main, modern method of producing glass. It combines the manufacturing process, using machines and vacuums, with age old techniques that were first utilised by Syrians in 100BC, ensuring that both quality and quantity can be adhering to with any type of glass. The likes of free blowing is what’s used for more specialised glass, such as antique mirror glass, whereas mould blowing is used for more widespread applications like kitchen interior design and glass splashbacks.

Much like other modern methods, the Westlake process mixes together the raw materials, whether it’s for heat resistant glass or coloured glass, into gobs of glass that then get poured into moulds, blowers and spindles, however, what sets the West. All of these cool down by moving in circular motions, going down a central column that is then gathered by a vacuum. Ther process continues with more and more blows of air before being transferred to a stemming machine that, as the name suggests, stretches the glass into necks and elongated shapes whilst gently reheating it. Finally, oxygen powered gas flames tend to any of the waste glass, otherwise known as moil, and then leaves the final product to cool and harden.

One of the main advantages of these processes is the impressive speed of manufacturing; some machines can make around 75,000 units a day. More unique, carefully crafted pieces are created by the free-blowing process more than mould blowing, as this process is mostly done by hand. Glassblowers adhering to the free blowing process can even swing their pipe to manipulate the shape of the piece whilst cooling it; a feat that would be hard to recreate via machinery.

Manufactured Glass: Flat Glass & Float Glass Process

The most common type of glass, used in homes, offices and more, is flat glass, which is often made adhering to the float glass process. First designed by Sir Alistair Pilkington in 1952, flat glass was developed to keep up with the demand for manufactured glass. There are six main steps for creating glass via the float glass process; melting & refining, floating, coating, annealing, inspecting and then cutting to order.

Melting & refining is the first and most important step of the float glass process, as the quality of the glass is determined at this stage and the likes of gas bubbles are removed and cleansed. Floating, the next step, is named so as the melted & refined materials is spouted onto a layer of liquid molten tin and this results in the high viscosity molten glass ‘floating’ atop it. After floating comes coating, which is when additional materials are added to the molten glass. These materials can vary wildly depending on what application the glass is required for, such as materials to bounce off UV rays for cars.

Next comes the annealing stage, where the molten glass is passed through long ovens of lowering heat levels so that the stress of the temperature difference doesn’t cause the glass any damage. Inspecting the cooled off glass comes next, which seems like a standard and obvious step to take but it’s a vital part of the process; even a single imperfection, like a grain of sand or a sole bubble, can greatly affect the quality of the final product. Finally, advanced computer programs and equipment are used to cut the gigantic glass sheets into separate pieces, custom cut to whatever purpose they’re needed.

There are almost as many methods of crafting and creating glass as there are types of glass themselves; everything from subtle skills required for antique mirrored glass to the mass production of coloured glass. A lot of talent goes into each and every sheet, so here at Carlen, we appreciate quality craftsmanship! For information on the many types of glass we stock, take a look at our products here, and for more news & articles about all things glass check out our blog.

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