John Fredrich Asmus

1990 Laureate, Cultural Heritage
United States, Born 1937

Project Goal

Develop laser techniques to clean and restore colour to China's ancient terracotta army

Location: China

Space Age Art Restorer

“Professionally I am known as an ‘art conservation scientist’,” says the 1990 Rolex Laureate of his unusual career fusing science, technology and art. “In fact, I have been acknowledged as the grandfather of laser art conservation, an epithet that I am extremely proud of.”

John Asmus, a research physicist at the University of California, San Diego, since 1973, traces his impressive body of work to the 1960s and what he calls the Star Wars-like Orion atomic energy programme. As one of the few scientists familiar with powerful lasers, he was part of the team charged with re-engineering atomic bombs for peaceful purposes such as propelling rockets.

“The Nuclear Test Ban Treaty of 1963 was a key element in the development of lasers,” explains Asmus. “No longer able to test atomic devices in space, weapons specialists turned to elaborate computer modelling to examine the effects of nuclear explosions. Lasers were used instead of the banned atomic weapons to simulate the explosions and to verify the computer codes. They were also essential in testing the scale model of the Orion deep-space rocket.”

Years later, Walter Munk, the celebrated oceanographer and Venice conservator, applied related computer modelling codes to the Adriatic tidal programme. Keenly aware that Venice was crumbling, he also considered how associated laser techniques could be used to preserve Venetian marble statues and monuments, which due to pollution were eroding at an alarming rate. Munk, a United States Defense Department advisor, had recently heard Asmus lecture on the then-revolutionary new technology, holography, and called on him for help.

In 1971, Asmus began collaborating with scientists and conservators at the Laboratorio San Gregorio in Venice to overcome immense technical difficulties and develop a way of making holographic images of the statues before they disappeared. The holograms that they successfully created with a ruby laser recorded the form, texture and other characteristics of these artworks in 3-D, thereby capturing them for posterity.

Asmus was then spurred on by an Italian colleague to devise a new technique to divest the statues of the black cloak that had built up on the marble over ages. His pioneering method using lasers to vaporise the sulphate encrustations without harming the stone underneath was hailed as an astounding advance by Kenneth Hempel, the world’s leading stone conservationist from London’s Victoria and Albert Museum. No one had ever before cleaned such objects with a laser.

Space-age Art Restoration
“This technology came straight out of the Orion programme,” says Asmus. “With Orion, we had to direct millions of watts of power at a rocket in order to propel it into space without destroying it. I hypothesised that it would also be possible to shoot this hundred-million-watt laser beam at a fragile statue and preserve its structure. By exploiting the unique attributes of a laser and controlling the device’s wavelength, energy and pulse length, I had developed a versatile conservation method that was selective, non-destructive and environmentally friendly.”

Based on his accomplishments in Venice, Asmus soon built a reputation as the “space-age art restorer”. “Conservators began seeking me out in the 1970s, as I was able to find solutions for ostensibly unsolvable problems,” he recounts. The technical developments that he instigated during his years at UC San Diego’s Center for Art/Science Studies (which became the Center for Research on Computing in the Arts in 1978) and, subsequently, on sabbatical for three years as Laser Department Manager at Maxwell Laboratories, helped trigger a revolution in art conservation.

Conservators, by nature a staid and cautious group, were sceptical about the use of modern technology, believing more damage had been done to works of art in the name of conservation than through all other causes combined. Asmus was able to overcome their resistance by demonstrating the benefits of technology in preserving objects and in deciphering art.

Between Art and Science
“Through the use of lasers, ultrasonics and image enhancement, my colleagues and I helped to broaden the scholarly foundation for art conservators and historians based on objective rather than subjective analysis,” he explains. “For example, computer imaging enabled us to create a picture of an artwork’s innermost layers and consequently reveal the artist’s creative process, the artistic techniques of that era, structural problems and even underlying earlier works of art.”

According to Asmus, the real marriage of technology and conservation began, fittingly, with a work by history’s greatest “mediator between art and science”, Leonardo da Vinci. In 1975, the pioneering physicist and his team at UC San Diego were invited to develop a specialised non-intrusive computer imaging method and apply it to the search for Leonardo’s long-lost, unfinished mural, “The Battle of Anghiari”, which was believed to have been painted on the walls of the Palazzo Vecchio in Florence. They succeeded in inventing an ultrasonic scanning system to locate fragmentary remains of the 500-year-old painting under a mural by Giorgio Vasari in the Palazzo’s Hall of Five Hundred. Ironically, it was the creation of this innovative digital ultrasonic technology, rather than finding the fragments, that proved most significant. A few years later, Asmus turned his attention to another Leonardo masterpiece, the enigmatic Mona Lisa.


Asmus regards his work on the Mona Lisa as the most personally satisfying of his career and the project that perhaps best exemplifies how serendipity has played such an important role in his life. James Arnold, famous for co-discovering radiocarbon dating and an early proponent of using technology in art conservation, encouraged him to probe beneath the painting’s brown layers.

To accomplish this, Asmus first had to obtain high-resolution colour photographs of the Mona Lisa from the Louvre and reproduce the masterpiece in digital form. His objectives were to “restore and correct” the colours digitally and to “remove” the centuries-old craquelure and varnish layers that were obscuring the work of art. Years later, after scanning the image into a supercomputer and applying a long and complex image-processing procedure, he discovered long-hidden details of the portrait, including pentimenti, or under-painting, suggestive of a hidden bead necklace beneath the layers of paint.

The implications of these discoveries were enormous, supporting key theories on the chronological position of the painting in Leonardo’s remarkable oeuvre, the identity of the model and the meaning of the portrait, which have long been shrouded in mystery.

“The results indicate a turning point in Leonardo’s work to a simpler, cleaner style,” Asmus relates.

“It appears as if he began this painting in 1503 or 1504 as a temporal female portrait and revised it over a period of six to nine years into a universal spiritual metaphor that continues to engage our imaginations today.”

Most important for Asmus, the Louvre recently announced that new x-rays of the Mona Lisa have confirmed his computer predictions of a hidden necklace made 15 years earlier, thus validating his imaging techniques.

Attacking an Army
In the 1980s, fate prevailed once again for Asmus when he was contacted by Wen Rei Tang of the Xi’an Electromechanical Information Institute in China. Wen, who had read about Asmus’ work, proposed that the American come to China to aid in the cleaning of the spectacular Qin Dynasty terracotta warriors, unearthed in 1974.

Asmus agreed and also suggested that they undertake a polychrome restoration programme, using pulsed laser radiation to restore colour to the life-size soldiers and return them to their original polychromatic splendour. It was for this conservation project that he was named a Rolex Laureate in 1990.

Asmus travelled to China in late 1989 and worked with Wen and his colleagues to design a special system for in-situ pigment chemical reduction for colour recovery. The physicist’s challenge was to build on his past experiences and devise a method to treat the fragile warriors without damaging them.

“This was an extremely painstaking and time-consuming process,” describes Asmus. “The Rolex funding allowed us to test the constantly evolving technology with increasingly more powerful and sophisticated lasers and helped finance the numerous technicians focused on the project in both China and the United States.”

More than a decade later, Wen eventually succeeded in recovering a few small vestiges of surviving polychrome on actual shards from the warriors. He and his associates have also successfully recreated the original colours by feeding the spectral data from these shards into a computer graphics system. Unfortunately, however, administrative delays have prevented Wen from travelling to the United States to carry out further research with a more advanced ultra-violet laser system designed by Asmus.

“I consider the project 80 per cent complete,” comments the Rolex Laureate, “as the technology has clearly worked. All that remains is for my Chinese colleagues to visit our lab and conduct additional experiments to automate the process. While I think this is unlikely to occur, the curator of the Qin site assures me that a plan is in place to restore the entire terracotta army within the next 150 years!”

A Rose Blooms Again

In 1992, while still waiting for Wen’s visit to California, John Asmus turned his attention to the ultrasonic imaging of Jay DeFeo’s “The Rose”, a 1,000-kilogram painting-cum-sculpture considered an icon of the Beat Generation in the late 1950s. When the artwork, which had taken eight years to create, began to crumble in the mid-1970s, it was encased in plaster for structural support and to slow its deterioration. Asmus was called in to assist in extracting the artwork safely from its plaster tomb and to restore it.

“Conserving this Beat-era artwork did not sound very appealing at first,” admits Asmus, “but I was proved wrong. All the major technologies I had used over the years — lasers, computer imaging and ultrasonics — came together. Surprisingly, “The Rose” is now considered a masterpiece and was chosen by Thomas Hoving, former director of New York’s Metropolitan Museum of Art, as one of the 100 greatest works of art in Western civilization. In many ways, I see the restoration of the “The Rose” as the culmination of my career.”

But Asmus’s groundbreaking endeavours carry on. The physicist finds it both remarkable and humbling how interest in the technology from his Rolex Award Chinese warrior project has exploded in the past five years and how dozens of organisations have lent financial support. Lasers for the Conservation of Art (LACONA), an international professional society devoted exclusively to art restoration with lasers, was formed in 1994 and today boasts 300 members. In concert with this mushrooming interest is the emergence of a new laser industry. More than a dozen firms now manufacture copies of the laser system he invented for the polychrome restoration work. Even his long-time associate, Italian architect and art conservator Giancarlo Calcagno, is currently employing the laser technique to clean and restore the world’s oldest mechanical clock, the 14th century Orologio Dondi, in Padua, Italy.

Full Circle
Today, Asmus’s work has come full circle and he is busy consulting on a project for the Culham nuclear facility in Britain. “I am helping to perfect a procedure for cleaning the world’s largest operating fusion reactor at Culham, by adapting the methods I used previously to remove toxic lead paint from steel bridges in Illinois and to decontaminate the Hanford atomic bomb plant in the state of Washington,” he notes. “Laser technology is an excellent means of tackling the world’s energy and pollution problems, particularly in cases like these that involve nuclear waste. Because the laser action is localised, it is easier to contain the hazardous material that is ejected.”

Asmus is also presently engaged in another environmental project with Clark Atlanta University in Georgia. The challenge, in this instance, is to remove the paint from the US Air Force Stealth bomber without damaging the surface and making it vulnerable to enemy radar.

Clearly, Asmus, a frequent lecturer and contributor to scientific journals, has little time for himself. Despite his best intentions, the book that he has been planning to complete for years remains just boxes of notes, for when a challenging project surfaces, he is always ready to lend a hand.

Asmus sees no contradiction in a career that has so closely combined physics and art, two disciplines that explore the interrelationship of space, time and light and are concerned with the nature of reality. “The chain of connections that led me from a degree in electrical engineering to become involved in art conservation may seem bizarre, yet this just serves as an example of how seemingly unrelated ideas and innovations interact to form a vast web of knowledge.”

Karen de Leschery

Other 1990 Laureates