THE FIRST EVIDENCE OF BURNING GLASS IN HISTORY
Pictured above: The Nimrud Lens, the oldest lens on Earth
Lenses have been used since the dawn of time to burn things and lit fires, simply by harnessing the power of the sun. Probably, in ancient times, we used vases filled with water as rays of sunlight catalyst, directing them to wood or straw. This was the beginning of a millenary history, when we controlled sun light in order to burn or carve!
The first lens that we know of is the Assyrian Nimrud Lens, a round piece of glass from the 8th century BC found in Iraq. It’s not sure whether it was used as a burning glass, yet there are some ancient Egyptian hieroglyphs depicting meniscus lenses. Since this first evidences, we started founding more mirrors or glasses used for different applications!
Strepsiades:"Have you ever seen this stone in the chemist's shops, the beautiful one you can see right through, they use to start a fire?"
Socrates: "Do you mean the burning-glass?"
Strepsiades: "I do. What if I took that glass, and when the scribe was writing out the charge, I stood between him and the sun - like this- some distance off, and made his writing melt, just the part about my case?"
Socrates: "By the Graces, that's a smart idea!"
Aristophanes - "The Clouds", a dialogue between Socrates and Strepsiades about burning glass - 5th century B.C.
The dialogue above is an excerpt of Aristophanes' “The Clouds”, a comedy written in 423 BC in Athens, Greece, for the City Dionysia, a sort of ancient festival in honour of the god Dionysus. The character of Strepsiades, a farmer persecuted by creditors, is considering to use a burning glass to erase his debt written on clay tablets. This dialogue marks the first written evidence of burning lenses, as a tool commonly used in daily life.
A DEFENSE WEAPON
An illustration of Ibn al-Haytham's book Thesaurus opticus depicting Archimedes' burning mirrors in act against the Roman Fleet
Another Greek who probably used burning lenses is Archimedes, who went down in history for his mathematical and engineering discoveries and inventions. According to the myth, in 212 BC he elaborated an ingenious strategy to defend the city of Syracuse from a naval siege by Romans. He got huge burning lenses installed on the walls of the city, which were used to incinerate Roman boats approaching the coast. Unfortunately, Greeks are known for their love for wine and the Roman army entered the city while the guards were celebrating the goddess Artemis.
This tale of Archimedes and burning glasses is told in a 6th century treatise written by Anthemius of Tralles, the geometer and architect who designed Hagia Sophia, the world biggest church (then mosque) of the Middle Ages.
Proclus Oneirocrites studied the lenses after being impressed by this tale. He purportedly used that same strategy to destroy the fleet of Vitalian during the 515 AC assault of Constantinople. As a matter of fact, it seems that the real treat Vitalian army had to face was a sulphur-based chemical close to Greek fire, and not the lens proposed by Anthemius, but the research upon lenses continued to improve.
SETTING OFF THE SACRED FIRE
Lighting a fire using the solar power is indeed a spectacular event with a magical and mysterious charm, that has really fascinated mankind during the centuries. That’s why burning glasses were also used during religious ceremonies, to set off some sort of sacred fire. For example, Saint Boniface used crystal lens concentrating the rays of the sun in order to light up the new fire of Holy Saturday during the Easter vigil. This tradition was kept by some Christians and burning glass were in use from the 7th century to the 16th century, during the rituals of Easter celebrations.
ADVANCING SCIENTIFIC PROGRESS
Illustration above: Lavoisier using a burning lens during an experiment in 1770
In more recent times, science took advantage of the lenses’ capacity to concentrate heat in a single point. This led to impressive discoveries during one of the experiments of French scientist Antoine Laurent Lavoisier. In 1774 he used a huge burning lens to discover oxygen, putting an end to the millenary beliefs of the 5 elements that compose the world: air, fire, water, earth, and ether. It was the beginning of modern chemistry, and all thanks to burning lenses!
Pictured here: The Odeillo Solar Furnace. Photo by H. Zell
Pictured here: Febo, a modern solar engraver to draw with the sun
AN EVERYDAY USE, FOR EVERYDAY CREATIVITY
Fifty years passed since the Odeillo solar furnace has been built and more than two millennia from Archimede’s burning mirrors, but what is the new frontier of burning glasses? We stopped using mirrors as weapons- and this is already good news - and we invented a way to use sun to create art! Febo is the first solar pyrography tool capable to convey the sun energy to draw on natural canvas such as wood, leather and cork. Like a solar furnace, it doesn’t need electricity to work and it’s the first pyrography tool that simply works by using a glass and the sunlight! Designed and produced in Italy, this simple yet inventive tool is allowing creatives around to world to express their artistic self thanks to the the solar power. At the very end of this long story of burning lenses we can finally create instead of destroy, with the use of this little, but powerful, tool!