Cylinder blown sheet glass
Cylinder blown sheet glass begins its life as a glassblower's breath. A skilled artisan blows molten glass into a long cylindrical shape, cuts off the ends, then slices down the side. That cut cylinder goes into an oven, where heat coaxes it to unroll, slowly and completely, into a flat sheet of glass.
This process is older than the machines that eventually replaced it. It fed the windows of homes and churches across Britain, France, and Germany for centuries. And tucked inside this story are a few surprises: desired imperfections, a wet piece of leather, and a patent filed in 1839 that changed how glassmakers fixed what the fire left behind.
Cylinder blown sheet shares its basic logic with a related method called broad sheet, but the cylinders here are larger. The glassblower shapes the molten glass into a cylinder, not a sphere or a pane. The ends are removed, a single cut runs down the length, and the oven does the rest.
The standard version of this method had a drawback. Flattening the cylinder and moving it caused surface damage to the glass. That meant every sheet had to be ground and polished before it was usable. The extra step was unavoidable, and it added time and labor to every piece.
Blenko Glass Company adapted the cylinder method using a process patented by William Blenko. His version introduced molds for the cylinder, which kept the size of each piece consistent. That was useful. But the more striking choice was what Blenko did with imperfection.
Slight flaws were not accidents to be corrected. They were intentional. Blenko wanted the finished glass to look like antique glass, and those small irregularities achieved exactly that effect. The company used this approach to make flat glass throughout the 20th century, producing sheets that looked old by design.
In 1839, the Chance Brothers invented what became known as the patent plate process. The method addressed the surface damage that the standard cylinder technique always produced.
Their solution was a wet piece of leather. A glass plate was placed on it, then ground and polished until the surface damage was gone. The Chance Brothers received a patent for this process, giving the broader industry a reliable way to finish cylinder blown sheets to a usable standard.
Cylinder blown sheet was one method among several for producing hand-blown window glass. Broad sheet, blown plate, crown glass, and polished plate all existed alongside it. These approaches persisted at least through the end of the 19th century.
The early 20th century drew a line between the old ways and the new. Hand-blown methods gave way to machine manufacturing on a broad front. Rolled plate appeared, as did machine drawn cylinder sheet. The Fourcault process introduced flat drawn sheet. Single and twin ground polished plate followed.
The most widespread replacement was float glass. Of all the machine methods that displaced hand-blown production, float glass became the most common. The centuries of cylinder blowing, Blenko molds, Chance Brothers leather, and careful grinding ended not with a single invention but with a wave of them arriving together at the start of a new century.
Common questions
What is cylinder blown sheet glass?
Cylinder blown sheet glass is a type of hand-blown window glass made by blowing molten glass into a cylindrical shape, cutting off the ends, slicing down the side, and placing the cylinder in an oven where it unrolls into a flat sheet. It is similar to broad sheet but uses larger cylinders.
How did Blenko Glass Company make cylinder blown sheet glass different?
Blenko Glass Company used a process patented by William Blenko that employed molds around the cylinder to ensure consistent sizing. Unlike the standard method, Blenko intentionally preserved slight imperfections in the finished glass to give it the appearance of antique glass.
What did the Chance Brothers invent in 1839 related to glass manufacturing?
In 1839, the Chance Brothers invented the patent plate process. It involved placing a glass plate on a wet piece of leather, then grinding and polishing the surface to remove the damage caused by flattening and moving the cylinder during production.
When was cylinder blown sheet glass manufactured in the UK?
Cylinder blown sheet glass was manufactured in the UK from the mid 19th century. Before domestic production began, Britain imported it from France and Germany, where it had been made since the 18th century.
What replaced cylinder blown sheet glass in the 20th century?
In the early 20th century, hand-blown methods including cylinder blown sheet were replaced by machine manufacturing. Alternatives included rolled plate, machine drawn cylinder sheet, the Fourcault process, single and twin ground polished plate, and most commonly, float glass.
What other methods of hand-blown window glass existed alongside cylinder blown sheet?
Broad sheet, blown plate, crown glass, and polished plate were all methods of producing hand-blown window glass that existed alongside cylinder blown sheet. These methods of manufacture lasted at least until the end of the 19th century.
All sources
4 references cited across the entry
- 1bookTransparencyDaniel Jutte — Yale University Press — 2023
- 2bookMaterials & Skills for Historic Building ConservationM. Forsyth — 2008