Glass-making also moved westward: by 1000 AD, Venice was a growing center of glass manufacturing.
In West Africa, local glass-makers at Igbo Olokun were making their own glass from sand, and making it into glass beads.
Glass-makers were still making both opaque and transparent glass. The opaque glass made millefiore bowls like this one. Millefiore means “a thousand flowers”.
How do you make millefiore bowls?
You make millefiore bowls by making glass rods in different colors. You melt five or six of those rods together, and slice them like slicing a loaf of bread. That makes the flowers. Then you layer the flowers in a mold, into the shape of a bowl. You heat the mold and the flowers all melt together into one bowl.
Another use for opaque glass was to make mosaic tesserae. In the Middle Ages, many people all around the Mediterranean were making big wall mosaics with scenes from the Bible, buildings, or patterns of flowers.
Using ashes instead of natron
In northern Europe, glassmakers went back to making glass using local wood ashes instead of natron. That way they could make their own raw glass using local sand, instead of buying it from Egyptian glass-makers.
The first eyeglasses
As Europe’s climate improved in the 1200s, Europeans got richer and more educated, and more people started to read, people in Italy began to use reading glasses about 1286 AD. In northern Europe, glassmakers made beautiful stained glass for cathedrals.
Mirrors and beads
While West Asia and India became too poor to pay for schools and books, Europeans were rich enough to spend money on education and scientific experiments. By 1550, Venetian glass-makers were making good mirrors, which they sold for a lot of money. Venetian glass-makers also made tons of pretty glass beads, which European traders sold to Native Americans and Africans in exchange for furs and people to enslave.
Telescopes and greenhouses
But, thanks to that same slave trade and colonization, Britain and France became richer in the 1600s. British and French glassmakers had the money to experiment, and they figured out better manufacturing methods like lead crystal and pouring molten glass instead of blowing it.
They also made the first telescopes. Galileo used one of those telescopes to see the moons of Jupiter and show that the earth really did go around the sun.
By the 1700s most glass-making moved from Venice to Britain and France. About 1800, glassmakers began to use steam engines to do a lot of the work, so big sheets of flat glass became cheaper. People started to have glass in their windows at home. Architects even built railroad station roofs out of glass! Glass greenhouses made it possible to grow vegetables in the winter.
Glass skyscrapers and computers
Soon everybody wanted glass for everything. French glassmakers began rolling glass on big iron tables in the 1830s. Then the British Henry Besemer figured out how to roll out a continuous ribbon of glass in the 1840s. British glassmaking got more and more mechanized.
Modern float glass
By the 1960s, British glassmakers invented modern float glass, where instead of iron rollers the glass is poured onto a river of melted tin. With this glass, you could build whole skyscrapers out of glass and steel.
Most glass today is made in China
But since World War II Britain is poorer, and most glass isn’t made in Britain anymore. Today, China makes than half the world’s glass, used for everything from computer screens to car windows and solar panels.
Did you find out what you wanted to know about medieval and modern glass? Let us know in the comments!
Learn by doing: scratch the backing off an old mirror to see what happens
More about Venice
How Glass Is Made, by Alan J. Paterson (1985). Easy reading, but it’s really about modern glass technology.
Studies in Ancient Technology: Leather in Antiquity – Sugar and Its Substitutes in Antiquity – Glass, by R. J. Forbes (2nd revised edition 1997). Only part of the book is about glass, but it will tell you everything you need to know about glass in ancient Greece and Rome. By a specialist, for adults.
Early Glass of the Ancient World: 1600 B.C.-A. D. 50, by E. M. Stern (1995). Marianne Stern is the leading world expert on ancient glass.
Roman, Byzantine and Early Medieval Glass: Ernesto Wolf Collection, by E. M. Stern and others (2002). Same expert author as above.