About a year ago, I told you that Italian scientists had developed the nanoscience of art restoration. Now, the same team from Florence has found a very innovative and gentle way 'for cleaning and conserving priceless oil paintings, marble sculptures and other works of art,' according to the American Chemical Society (ACS). They've mixed nanoparticles of cobalt and iron oxide with a polymer gel to build these nanomagnetic sponges (scroll to article #2). 'The sponges can be loaded with solvents and other cleaning agents, and cut with a knife or scissors into desired shapes for application to specific, soiled areas of a painting. When the cleaning is done, conservators can remove the gel with a magnet.' Besides art restoration, these nanomagnetic sponges could be used in cosmetics, detergents or biotechnology.
This technology has been developed at the Center for Colloid and Surface Science (CSGI) research group at the University of Florence, directed by Piero Baglioni. The pictures above describe "the application of the nanomagnetic gel to a fresco painting realized in the laboratory for testing the gel efficacy for paraloid B72 removal." The left image shows the gel treatment under normal light while the right one shows the area cleaned by the removal of paraloid B72 under a grazing angle light. (Credit: Piero Baglioni and his colleagues)
In "Nanomagnetic sponge restores filthy frescoes," New Scientist provides additional details. "The cleaning technique itself is simple: the researchers coat an area with a few millimetres of gel and leave it for between 10 minutes and an hour, depending on how dirty the artwork is, before removing the film with an ordinary bar magnet (see image, top right). The gel can then be dried and reused. 'The beauty of the new technique is that the gel is not sticky,' Baglioni told New Scientist. 'And because it is magnetic, it can be removed using an ordinary bar magnet once it has cleaned a surface. An important point is that the magnet only needs to be brought close to the gel itself and does not need to touch it, which means the cleaning process is particularly suited to precious artifacts.'"
And in "Magnets harnessed to clean artwork," Nature also gives more information. "Baglioni's gel consists mainly of a polymer (polyethylene glycol and acrylamide) impregnated with iron nanoparticles. This gel is firm enough to be cut with scissors into 'sponges' of specific shapes required for cleaning. Such sponges can be loaded with a wide array of cleaning materials, as required for oil paintings or marble sculptures for example, and applied to the parts of the artwork that need cleaning. Once applied, the cleanser leaches onto the top surface of the artwork, where it should dissolve the dirt to be removed. As the upper surface of the gel dries during the cleaning process, an osmotic pressure gradient is set up within the gel that then pulls the cleaning solution back into the sponge and away from the surface of the painting or sculpture. This trick works thanks to the fact that the gel is generally more inclined to soak up water-based substances than the surfaces being treated. Simply placing a magnet above the piece of gel then removes it from the painting's surface without damaging the art."
This research work has been published in ACS's Langmuir journal under the name "Nanomagnetic Sponges for the Cleaning of Works of Art" (Volume 23, Issue 17, Pages 8681-8685, Published online on July 11, 2007). Here is the abstract. "This letter reports the synthesis and characterization of functionalized magnetic nanoparticles associated with chemical gels and their application to the conservation of cultural heritage. Magnetic nanoparticles, which are associated with acrylamide ethylene oxide polymers, produce a sponge that can be loaded with oil-in-water microemulsions, forming a magnetically responsive gel-like system and acting as a permanent hydrogel. The magnetic gel-like system can be used for specific applications in detergents or in the release of the loaded material. The system can be magnetically manipulated and cleaned from the loaded materials and then dried and reused for a different application. We report an important application of this new nanomagnetic responsive material in the field of cultural heritage conservation."
This technical paper is only available to paid subscribers on the Langmuir website, but the American Chemical Society (ACS) provides a link to this article (PDF format, 5 pages, 693 KB) from which the above pictures have been extracted.
Sources: ACS's Weekly Presspac, August 29, 2007; Belle Dumé, New Scientist, September 3, 2007; Daniel Cressey, Nature, September 3, 2007; and various websites
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