Conservators use heat transfer for restoration – from paintings, works on paper and textiles to murals, 3-D objects and more. But conventional methods leave much to be desired. An EU-funded project has developed a revolutionary heating system based on carbon nanotubes and silver nanoparticles. Early results show superior performance, unsurpassed accuracy and lower impact.

Although the word ‘timeless’ is often associated with eminent works of art, they, like everything else, degrade irreversibly with age. Conservation aims to slow down the process of physical alteration and routine problems associated with changes in materials (discoloration, yellowing or opaque coatings, deformations, delamination, cracking or cupping of paint film and more).

Art conservators often apply mild heat in combination with other treatments or tools, such as pressure, vapours, adhesives and even enzymes that remain ‘dormant’ at room temperature. Yet heat must be applied very carefully and in a controlled manner – a lack of control can result in ineffective treatment or – worse – damage to the artwork.

Conventional heat transfer methods using irons, water bags, heated sand or even heating tables are inaccurate, with erratic heating that is difficult to control. The field of art-conservation urgently needed mobile, precise, selective and safe heat transfer technology.

The EU-funded IMAT project turned to nanomaterials for this technology. “The conservation field has minimal resources for advanced technological development, and could not have addressed the need without EU support,” says paintings conservator and project co-leader Tomas Markevicius. The three-year project, coordinated at Italy’s Universitià degli Studi di Firenze, united art conservators, researchers and nano-technologists to develop a revolutionary heat transfer system tailored for art conservation. The team expects the result to be a “game changer” for conservation.

The resulting system has unprecedented capabilities. Essentially a mat thin enough to be placed directly on the artwork, the IMAT can be carried in a small case and works with only 36 V (which cannot be felt through human skin).

The electrically conductive mat can be breathable and transparent. It heats to 85°C or more in an instant, while the heating cycle can be programmed with great precision – more than conservators would need. Also, the heat is evenly distributed over the surface, the temperature remains ultra-steady, and controllable to within 0.25 of a degree or less. The project also developed an accompanying touch-screen control console to monitor and control the heat transfer cycle.

Astounding material

Key to the achievements are carbon nanotubes (CNTs) and silver nanoparticles. A relatively new material, CNTs are super-thin tubular structures of carbon atoms. They are 50 000 times thinner than human hair, and just 1 gram of nanotubes could circle the Earth three times if placed in a continuous line. They have many remarkable properties, including unmatched stiffness and strength. The IMAT project utilised their supreme electric and thermal conductivity.

An ultra-low voltage input produces a lot of useable heat. Furthermore, with the temperature sensor and control unit adjusting the mat’s temperature 20-30 times per second, together with the material’s nearly instantaneous thermal response to the current, the heat application remains stable and accurate.

Nanotubes and silver nanoparticles also give IMAT its permeability to gases (air and vapours) and also transparency, which allows complete visual control over the conservation work.

Earlier heat-treatment devices required substantial voltages of up to 380 V, and power of up to 15 000 Watts – neither available nor allowed in most European historical buildings. IMAT’s meagre 36 V makes the system safe to use with a normal power supply, and even able to operate on batteries or from a car power supply.

The device’s greatest benefit is that it allows conservators to carry out minimal, targeted and safer treatments, improving the condition of the damaged artwork and preserving it for future generations.

Art works are entangled in history. Modern conservation may be the latest in a series of measures going back centuries. Those efforts are as much part of the work as what the artist intended, and must also be preserved. 

IMAT makes that possible, and the prototype has been successfully demonstrated in more than one important conservation – the 18^th century painting Maria Luisa Infante di Spagna, by Lorenzo Tiepolo. The painting needed treating for stiffly cupped paint plus delamination. Conservators employed IMAT’s gentle heat combined with humidity over a long period to smooth the surface.

“Twenty five years ago, that restoration would have been invasive,” says paintings conservator and project co-leader Nina Olsson. “It would have involved impregnating the canvas with adhesive and destroying its visual and material authenticity.” IMAT achieved superior results, and in a very low-impact way using far less invasive methods.