ETU “LETI” Developed a Laser-Based Technology to Restore Cultural Heritage Assets Made of Steel

ETU “LETI” Developed a Laser-Based Technology to Restore Cultural Heritage Assets Made of Steel

This technology uses laser processing to restore the blued finish on the works of decorative and applied art made of steel.

25.04.2024 109

Many cultural heritage objects made of steel (household items, weapons, caskets) include elements with a special decorative coating – the so-called bluing. This technique was often used in the XVII-XIX centuries. It is based on heat treatment of metal: under the influence of high temperature, oxide films appear on the surface of steel and, depending on the thickness of the film, change its colour to blue, black or, less often, yellow. As a result of poor storage (for example, due to high humidity), over time, pockets of corrosion appear on the surface of the item, which partially or completely destroys the decorated areas, changing the aesthetic properties of the object.

The traditional method to restore damaged cultural objects made of steel consists in using chemical reagents, which is ineffective and, in addition, can negatively affect the restorer’s health due to the toxicity of the substances. Another method, surface thermal heating, is not safe for the cultural object itself, since it can melt the surface. In addition, the item, for example a casket, can be composite, consisting of wood, additional inserts of metal and precious stones, pearls, enamels, which greatly complicates the task of thermal or chemical processing of the object.

Therefore, researchers all over the world are trying to develop new safe ways to restore bluing and return the item its original appearance.

“We have developed a laser restoration technique that can restore the lost bluing of a cultural heritage object made of steel, for example, the hilt of an ancient sword or the handle of a pistol. This approach allows us to clean the metal surface from any contamination with high accuracy, polish it and protect it from new damage. But most importantly, by combining all three types of laser processing and optimizing the laser radiation parameters, we can restore the original colour of the finish, without any damage to the other parts of the item.”

Vadim Parfenov, Head of the LETI Laser Lab laboratory, Professor of the Department of Photonics and the Department of Laser Measuring and Navigation Systems (LMNS) of ETU “LETI”

According to the scientist, in the beginning the experts tried to get a range of colours by processing the surface of carbon steel with a laser. It turned out that by using different temperatures, i.e. by using different laser radiation parameters, it is possible to change the thickness of the oxide film and, in this manner, to vary the colours of the steel surface finish. This has shown that with the help of laser processing, it is possible to replicate the bluing technique. After that, the scientists tried using laser-cleaning technology to remove the corrosion layer from the experimental steel samples. As a result, an integrated approach to the restoration of blued steel cultural objects was developed.

“Military-Historical Museum of Artillery, Engineer and Signal Corps has expressed interest in our work. Before processing their museum exhibits, we applied our technology to carbon steel samples, which showed significant results. At the moment, we are going to move on to the next stage and, together with the museum restorers, to restore the bluing on authentic historical objects.”

Vadim Parfenov, Head of the LETI Laser Lab laboratory, Professor of the Department of Photonics and the Department of Laser Measuring and Navigation Systems (LMNS) of ETU “LETI”

This technology is the result of many years of work carried out by the laser technology specialists of the LETI Laser Lab laboratory. The laboratory was founded as part of the ETU “LETI” Priority 2030 development program.

Mkhmad Salhab, a graduate student of the Department of Photonics, takes part in the development of laser-based technology to restore blued steel cultural objects. Mkhmad presented the project in the Student Startup Program of the Innovation Promotion Foundation and won a grant of a million rubles. The requirements for the participants included registration of an LLC, development of a website in order to popularize the project and patent protection.

The results of a study on laser restoration of blued steel cultural objects were presented in the scientific journal Quantum Beam Science and at the Seminar on Fields, Waves, Photonics and Electro-optics: Theory and Practical Applications (FWPE) conference.

 


Anastasia Mustafina, a 4th-year student of the Faculty of Humanities of ETU "LETI"