Early modern glass in England facts for kids
The early modern period in England, from about 1500 to 1800, saw a big comeback in making glass. Before this, in medieval times, glass production was small-scale. It mainly involved making "forest glass" for windows and containers, mostly in a place called the Weald.
Over time, glassmaking changed from small family businesses to large companies. These big companies were often given special rights by the King or Queen. New people arriving from Europe brought fresh ideas for furnaces and raw materials. This helped create much better quality glass. Later, rules from monasteries stopped the use of wood for fuel. This led to using coal instead, which was cheaper. By the late 1600s, the invention of "lead glass" made England a leader in the glass industry. This also helped set the stage for the Industrial Revolution.
Contents
How Glass is Made
Glass has three main parts. First, there's a network former, which is usually silica (like sand). Second, a network modifier, also called a flux, helps the glass melt at a lower temperature. Third, a network stabilizer, mostly lime, makes the glass strong and stable.
In the 1500s and 1600s, making glass from raw materials and shaping it into objects often happened in the same workshop. Old, broken glass, called cullet, was also recycled and melted down.
The network former came from fine or coarse sands. These sands were usually found close to where the glass was made. Sometimes, silica-based pebbles were used too.
Network modifiers changed the glass's makeup and lowered its melting point. Different types of glass used different fluxes. For example, potassium oxide (K2O) from plant ash was widely used.
The type of flux chosen greatly affected the glass quality. For "forest glass" in England, ash from beech and oak trees was popular. For soda-lime glass, alkalis came from marine plants. These included local kelp or plants imported from warmer places like the Mediterranean. These plants helped make clear, colorless glass called crystallo or façon de venise, which was the best quality.
Network stabilizers like lime continued to be used. Lime is naturally found in most sands. It could also be added on purpose to the glass mixture.
Types of Glass
Experts have found five main types of glass from this period. These can be grouped into "green glass" and "white glass."
- Potash-lime-silica glass: This is often called "forest glass" or "green glass." It has a lot of potassium oxide.
- High lime low alkali glass: Also a "green glass." It has less sodium and potassium, but more calcium oxide.
- Soda-lime glass: This is a "white glass" or "ordinary glass." It has low magnesium and calcium, but high potassium.
- Mixed alkali glass: This is a "white glass" or crystallo. It has lower levels of sodium, potassium, and calcium than other types.
- Lead glass: This is a "white glass" or façon de venise. It contains a lot of PbO (lead oxide).
Glass Colors
Many things could change the color of glass. These included natural impurities in the raw materials, how hot the furnace was, and special ingredients added on purpose.
Iron found in sand could make glass green or brown. This depended on how much oxygen was present during melting. Smoke from burning coal could add carbon, making the glass dark brown or black. Manganese, found in wood ash, might have given glass a lighter, see-through green color. Other tiny amounts of elements in the alkalis also affected the final color.
Early Glassmaking Workshops
Old glassmaking traditions continued in the Weald area. But by the early 1600s, this area was losing its forests. So, glassmaking spread to other places with plenty of wood for furnaces. These new areas included Hampshire, Gloucestershire, North Staffordshire, and the Scottish Borders.
At Bagot's Park in Staffordshire, an old glass workshop from around 1535 was found. It had a main melting furnace and a smaller furnace for cooling glass. The melting furnace had special benches for three large pots, called crucibles. A central air channel helped the furnace reach very high temperatures (1200°C) to melt the glass. Cooling the glass and glass blowing likely happened in the smaller furnace. Piles of broken glass (cullet) were found nearby. This suggests they used a flux to help the glass melt at lower temperatures. The glass found here was damaged, but pieces of broad glass and crown glass show that both window panes and vessels were made.
Glassblowing Techniques
Most glass during this time was shaped by blowing or mould blowing into different vessel shapes. Glassmakers added decorations like optic patterns or by trailing thin lines of glass. Sometimes, they used pre-made glass rods to copy fancy Venetian styles.
Ideas from Europe
In 1567, a man named Jean Carré came to London from Antwerp. He got a special permission from the Crown to make window glass. The rule was that prices had to stay low. Also, he had to teach English people how to make and blow glass. He brought many skilled Venetian glassmakers to his London workshop. He also opened another furnace outside the city to make vessels and green glass.
Later, in 1574, Jacob Verzelini, a Venetian who worked for Carré, was given a monopoly. This meant he was the only one allowed to make Venetian-style vessel glass. This stopped most glass imports from Venice and encouraged local English glass production. Verzelini wanted to make clear crystallo glass and fancy façon de venise glass. He did this by importing barilla (a plant ash) from Spain. This helped lower the price of clear glass. It made beautiful glassware available to more wealthy people and the middle class.
Small-scale production of everyday "green glass" continued. Many workshops in different areas made it for local use, following the old "forest glass" tradition.
New Furnace Designs
From the mid-1500s, glass furnaces began to look more like those on the European continent. This change is seen in old workshop remains. It supports the idea that immigrant glassmakers brought new designs.
Some furnaces from the late 1500s and early 1600s had "wing-like" additions. These were found at Hutton and Rosedale in York, and Vann Copse in the Weald. The Hutton furnace had two wings added to its original rectangular shape. A smaller furnace nearby was stopped around the same time. This suggests the wings were used for cooling glass or pre-heating pots.
The furnaces at Rosedale and Vann Copse were built similarly but with four wings, one in each corner. These wings were part of the main furnace. Evidence showed they were heated, meaning they were also used for preparing materials or shaping glass. The glass from Rosedale was generally cleaner and better quality than Hutton's. The reasons for this are not fully known. Rosedale seemed to produce more glass than Hutton. Two extra smaller furnaces show that the operation had grown. These furnaces are thought to be like the Lorraine style from Belgium.
Switching to Coal Fuel
Between 1581 and 1584, the English Parliament became worried about the country's wood supply. Many industries that needed high heat, like glassmaking, relied on wood. This was quickly using up England's forests. At first, a rule said you could only use wood from your own land.
By 1609, Sir Edward Zouche got permission to try using coal as the main fuel for a furnace in Winchester. By 1615, Parliament completely banned the use of wood for fuel.
Using coal created new challenges for glass production. Coal fires produced short flames. This meant the hottest part of the furnace moved from the ends to the center. Also, air currents were needed to keep the heat high enough to melt glass. Early coal furnaces, like one at Bolsterstone, had underground channels to remove ash easily.
Another problem was that carbon from coal fumes could get into the glass. This happened if the glass pots were not covered. It made the glass dark and often uneven in color. So, lids, like those found at Bolsterstone, had to be used to keep the glass clean. Glass bottles from this early time are often dark.
Sir Robert Mansell and Glassmaking
Before 1616, Sir Robert Mansell bought the company and special permission started by Zouche. He began many glassmaking projects. He set up a successful glass workshop near a coal source. This helped him save money and meet London's growing demand for glass. His crystallo furnace in Broad Street, London, did very well. Some of his earlier attempts to build new furnaces failed because transport costs were too high. However, the furnace Mansell set up in Newcastle was successful.
Another winged furnace was built at Kimmeridge. It used local oil shale as fuel. Unlike other winged furnaces, this one had deep air channels and a central fire pit. This shows how they adapted to the new fuel source. This furnace was torn down in 1623 because it broke Mansell's monopoly (his exclusive right to make glass).
Conical Glasshouses
In the late 1600s, England's conical glasshouses introduced chimneys and a new shape for furnaces. This idea might have come from earlier "wind furnaces" or beehive-shaped Venetian furnaces. The chimney created a strong draft and helped remove coal fumes. The first examples of these furnaces were found in Bristol and Gawber, Yorkshire.
These furnaces had underground air channels and chimneys with air holes. This created a strong air flow to control the heat. Steps like preparing materials, pre-heating pots, and cooling glass happened in different parts of the furnace, raised above the heat source.
Growing Glass Industry
Around 1663, George Ravenscroft created "flint glass." This was a clear, see-through glass with many good qualities for working with. His first recipe had a problem called "crizzling," where the glass would crack. Later, he added PbO (lead oxide), which fixed this problem. This created a much better glass that was perfect for engraving and etching. When Ravenscroft's special permission ended, lead glass was widely adopted by the Glass Seller's Guild.
Lead glass helped England become a leader in the glass industry. Wine bottles and small glass containers began to be made and sent out to other countries in large numbers. The remains of the Albion shipwreck from 1765 contained 11 lead glass ingots. These are thought to have been meant for trade with China. This suggests that lead glass was an important English export.
The 1800s brought new inventions, like gas fuel. Also, continuous melting in large tank furnaces marked the end of the early modern period and the start of the Industrial Revolution.
English Glass Objects
Glass objects became more detailed and specific for their use during this period. Mirror glass and other glass items also began to be made in larger amounts. Types of objects included:
- Small bottles (phials)
- Goblets
- Drinking glasses
- Beakers
- Tankards
- Jugs
- Bottles
- Bowls
- Jars
- Urinals
- Flasks
- Mirrors
Window Glass
Window glass was made in small amounts throughout this time. It came in forms like crown glass and broad glass. Most of it was "green glass" during the 1500s. While rare in the early 1500s, glass windows soon became a sign of growing wealth and importance. Larger sheets of glass were in demand for homes and public buildings.
Stained Glass
In the earliest part of the early modern period, stained glass was brought into England from France. With the Protestant Reformation in England, churches started using more expensive "white" (clear) glass instead of colored stained glass.
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