Frescoes
By Angelika Franz
A team from the University of Michigan has been working to develop applications for terahertz ray waves. The researchers have seized upon an application that is peaceful, clean, beautiful and of cultural value: old wall paintings. Over the course of time, countless colorful images on the walls of churches or palaces have been painted or plastered over. Until now, there's been no way to detect these images, rendering them as good as lost.
But initial tests have shown T-rays are able to detect penciled sketches under layers of both paint and plaster. Come March, the Michigan team is taking their show out of the lab and onto the road. Working with specialists from the Louvre, the team will pay a visit to the Church of St. Jean Baptiste in Vif, France. Frescoes from the 13th and 14th centuries were recently discovered under five layers of plaster on the walls of the 13th-century church. After their first attempts to expose the frescoes, the conservators gave up. Now they are awaiting the help of the physicists from Michigan.
"Terahertz is a strange range in the electromagnetic spectrum because it's quasi-optical. It is light, but it isn't," Bianca Jackson told photonics.com, which follows developments in the optics industry. Jackson is writing her Ph.D. dissertation on terahertz and recently published the results of her research on color in the periodical Optics Communications.
After a Lost Da Vinci
The team's T-ray system was developed at Picometrix, a company based in Ann Arbor, Michigan. It sends ultra-fast laser pulses to a semiconductor antenna, which in turn emits pulses of T-rays. The rays then penetrate the plaster, and a certain proportion of them are reflected back from the underlying layers. The type of material beneath the plaster is determined by how quickly the rays are reflected and by how much energy they have retained. Paints of different colors have their own characteristic signals. A receiver measures the reflected energy, and the data is used to determine the image hidden beneath the top layer, Jackson told photonics.com.
...Jackson's dream is to help search for Leonardo da Vinci's lost work "The Battle of Anghiari." For generations, art historians have frantically searched for the unfinished painting. They suspect that it might lie behind a wall painting of Giorgio Vasari in Florence's Palazzo Vecchio.
When Jackson speaks about the lost Da Vinci work, you can hear the excitement and anticipation in her voice. Engineer Maurizio Seracini is currently examining the suspected layers with a neutron scanner. "We're trying to make contact with Seracini to see if he'd like to cooperate," Jackson told SPIEGEL ONLINE. "We'll surely get a lot further with terahertz than with neutrons."
Marie Mourou
Freeing frescos: In the Church of St. John the Baptist in France, restorers uncovered initial traces of this hidden artwork. Further tests await a team of scientists from Michigan.
Bianca Jackson
A saint's picture is concealed under layers of ancient paint and plaster.
Marie Mourou
A reconstruction of what the hidden image might look like.
Bianca Jackson
The "T-ray" sets researchers on the right track ...
Marie Mourou
... and helps restorers reconstruct the face of another saint.
By Angelika Franz
A team from the University of Michigan has been working to develop applications for terahertz ray waves. The researchers have seized upon an application that is peaceful, clean, beautiful and of cultural value: old wall paintings. Over the course of time, countless colorful images on the walls of churches or palaces have been painted or plastered over. Until now, there's been no way to detect these images, rendering them as good as lost.
But initial tests have shown T-rays are able to detect penciled sketches under layers of both paint and plaster. Come March, the Michigan team is taking their show out of the lab and onto the road. Working with specialists from the Louvre, the team will pay a visit to the Church of St. Jean Baptiste in Vif, France. Frescoes from the 13th and 14th centuries were recently discovered under five layers of plaster on the walls of the 13th-century church. After their first attempts to expose the frescoes, the conservators gave up. Now they are awaiting the help of the physicists from Michigan.
"Terahertz is a strange range in the electromagnetic spectrum because it's quasi-optical. It is light, but it isn't," Bianca Jackson told photonics.com, which follows developments in the optics industry. Jackson is writing her Ph.D. dissertation on terahertz and recently published the results of her research on color in the periodical Optics Communications.
After a Lost Da Vinci
The team's T-ray system was developed at Picometrix, a company based in Ann Arbor, Michigan. It sends ultra-fast laser pulses to a semiconductor antenna, which in turn emits pulses of T-rays. The rays then penetrate the plaster, and a certain proportion of them are reflected back from the underlying layers. The type of material beneath the plaster is determined by how quickly the rays are reflected and by how much energy they have retained. Paints of different colors have their own characteristic signals. A receiver measures the reflected energy, and the data is used to determine the image hidden beneath the top layer, Jackson told photonics.com.
...Jackson's dream is to help search for Leonardo da Vinci's lost work "The Battle of Anghiari." For generations, art historians have frantically searched for the unfinished painting. They suspect that it might lie behind a wall painting of Giorgio Vasari in Florence's Palazzo Vecchio.
When Jackson speaks about the lost Da Vinci work, you can hear the excitement and anticipation in her voice. Engineer Maurizio Seracini is currently examining the suspected layers with a neutron scanner. "We're trying to make contact with Seracini to see if he'd like to cooperate," Jackson told SPIEGEL ONLINE. "We'll surely get a lot further with terahertz than with neutrons."
Marie MourouFreeing frescos: In the Church of St. John the Baptist in France, restorers uncovered initial traces of this hidden artwork. Further tests await a team of scientists from Michigan.
Bianca JacksonA saint's picture is concealed under layers of ancient paint and plaster.
Marie MourouA reconstruction of what the hidden image might look like.
Bianca JacksonThe "T-ray" sets researchers on the right track ...
Marie Mourou... and helps restorers reconstruct the face of another saint.
"I have a mustard- seed; and I am not afraid to use it."
[Ratzinger:"Salt of the Earth"]
May Our Papa's radiant-light continuously shine forth to illuminate Christ for the world!
[Ratzinger:"Salt of the Earth"]
May Our Papa's radiant-light continuously shine forth to illuminate Christ for the world!
