Modern Glass Production
One big step forward in glassmaking came when lead oxide was added to molten glass. This didn’t just make the glass look better. It also made it easier to melt using sea coal in the furnace. On top of that, it gave glassmakers more time to work with the material before it hardened, which made shaping and handling simpler.
George Ravenscroft figured this out in 1674. He was the first person to make clear lead crystal glass in large amounts. He had the right connections and enough money to make serious changes in the glass trade. Thanks to him, England ended up taking the lead from Venice as the main center for glassmaking during the 1700s and 1800s.
Ravenscroft wanted to find a solid alternative to Venetian cristallo, so he tried using flint as his source of silica. The problem was, the glass he made with it often cracked. It would develop thin webs of fractures, which ruined its clarity. He got around this by swapping some of the potash in the mix with lead oxide. That fixed the issue and gave the final product a smooth, clear finish.
He got a patent for his method and started making and refining his glass in a factory at the Savoy. Later, he moved production to Henley-on-Thames, where things could run more quietly.
By 1696, when the patent ended, twenty-seven glass factories across England were already making flint glass. They were shipping it all over Europe. It did so well that, in 1746, the British government started taxing it. But instead of lowering the lead content to cut costs, glassmakers found another way. They made smaller, more delicate pieces that were rich in detail. These often had hollow stems and are known today as Excise glasses. The tax stayed in place until 1845. Once it was finally lifted, the British glass industry took off.
As far back as 1620, people in London were using the blown plate glass method to make glass for mirrors and carriage windows. But it wasn’t until 1688 that the French, led by Louis Lucas de Nehou and A. Thevart, really refined things. They came up with a new process to cast polished plate glass. Before that, mirrors were made with blown glass sheets that couldn’t be very large. Nehou’s team poured molten glass onto a flat iron table and rolled it out. That let them make big glass plates for the first time.
In 1773, the English adopted this method at Ravenhead. Then, around 1800, they started using steam engines to grind and polish the glass. That turned the polishing stage into a full industrial process and made it easier to handle on a bigger scale.
Glass as a Building Material
The use of glass in construction took a big leap forward with the Crystal Palace in 1851. Joseph Paxton built it to house the Great Exhibition. That structure changed how people thought about glass. It showed that glass could be used on a large scale, not just for decoration but as a main part of a building. After that, glass started showing up more often in homes and greenhouses.
Before this, in 1832, the British Crown Glass Company, which later became Chance Brothers, started using the cylinder method to make sheet glass. They got help from Georges Bontemps, a well-known French glassmaker. This process involved blowing glass into long cylinders. The cylinders were sliced open lengthwise, then flattened on a cast iron table and slowly cooled down, or annealed, to prevent cracking.
Another type, plate glass, was made by pouring molten glass onto a cast iron surface and rolling it flat. While still soft, the sheet was fed into a lehr, a long tunnel-like oven that slowly cooled the glass. A roller system moved the glass through the tunnel. In 1847, James Hartley came up with the Rolled Plate method, which gave the glass a ribbed texture. This was perfect for things like big glass roofs in railway stations.
Early Automation in Glassmaking
The push to automate glassmaking started early. Henry Ricketts, in 1821, patented a glass molding machine. Then, in 1848, engineer Henry Bessemer came up with a method to make a continuous ribbon of flat glass by passing it between rollers. His idea was bold but costly. The glass needed polishing after rolling, which made the process expensive. Robert Lucas Chance of Chance Brothers tried it but gave up because it wasn’t practical at the time.
Back in 1843, Bessemer had also introduced an early version of float glass. He poured molten glass onto liquid tin, but the method wasn’t fully successful until much later.
Mass production of glass took a big step in 1887. A company called Ashley in Castleford, Yorkshire, developed a semi-automatic system. Their machines could make around 200 identical bottles every hour. That was way faster than traditional methods. A year later, in 1888, Chance Brothers started using machine-rolled techniques to create patterned glass.
New Types and Better Methods
By 1898, Pilkington came up with Wired Cast glass. It had steel wire mesh inside for extra strength and security. People often call it "Georgian Wired Glass," but that’s misleading. It came long after the Georgian period.
Around 1910, Pilkington brought the machine-drawn cylinder technique to the UK. This was the first fully mechanical way to draw window glass. The idea came from the United States, and Pilkington made it work under license.
Then, in 1938, Pilkington took things a step further. They improved the polished plate method by using a double grinding process. That made the surface smoother and the quality better overall.
The Rise of Float Glass
Between 1953 and 1957, Sir Alastair Pilkington and Kenneth Bickerstaff developed the float glass method. This was the first system that could form a steady ribbon of glass by letting it float over molten tin. The glass spread out evenly under its own weight. This gave the final sheet a uniform thickness and a flat, clear surface. The result was high-quality glass that didn’t need extra polishing.
This changed the industry. Most windows today are made using the float glass method. Most float glass is made from soda lime, but the same method is used for smaller batches of borosilicate and display panel glass, too.
What made float glass work was keeping the right amount of molten glass flowing onto the tin bath. The weight of the glass kept it flat as it cooled. It took a few years, but by 1960, Pilkington was selling float glass on a large, profitable scale.
