gh SALUTARY CHEMISTRY

Special polyacrylates-based polymeric coating allows restorers to protect every speck of the surface of an ancient fresko, terracotta statuettes or a garden sculpture, as well as other porous materials. The polymers are being developed by Russian chemists - specialists of Nizhni Novgorod State University.

Originality of a new development is the fact that restorers will now be able to apply an individual approach to each article made of clay, stone, concrete or any other porous material which is to be preserved and/or restored. Knowing what the article is made of, restores will be able either to select the most appropriate coating composition or to ask chemists to synthesize a polymer with required properties. Chemists, in their turn, will have a peculiar reference book. The reference book will help to determine the polymer whose structure will possess the required properties, and the best way to process a fresco or a crock from nomads' burial mound with this polymer.

"As a matter of fact, restores have to work practically "blindfolded" so far, says chief of research D.N. Yemelyanov, Professor (Nizhni Novgorod State University). There is still no common scientific approach to selection of coating material and to the application method. A collection of empirical knowledge is available - results of years of work by trial and error method, which the restores pass on from hand to hand, from lit to lip. There are several types of compositions available for surface processing - they are all foreign and certainly patented. There are practically no Russian compositions to be used, and those available are far from irreproachable. How to produce good compositions, what they should be made of, what polymer suits better for solving a specific task - these are the questions we are seeking answers to."

It may seem that it makes no difference what to use to dissolve the polymer before impregnating with it the surface of, for example, a statuette of unburnt brick, a toy of a ancient nomad's son or daughter? The dissolvent will dry up all the same, and only the polymer will remain on the surface. The authors have proved that is works absolutely different! If the protective film should be created only on the surface, it is better to use such a dissover that polymer molecules would roll up into "small balls"-globules and would not "creep" deeply into the material. If the material needs to be deeply impregnated, then a polymer "good" to dissolver should be chosen - so that molecules would straighten up, become flexible and crawl into pores. Or the other way round, the "worst" one should be applied - so that the polymer totally "shrinked" and its molecules would become small solid balls to penetrate the narrowest pores.

Now the researchers are working to discover regularities that would bind structure of the polymer and its properties, on the one hand, and properties of the material being restored and the restorer's task, on the other hand. They draw tables and diagrams for restores to facilitate their choice of the best-of-breed polymer for preservation or restoration of articles made of stone, clay, paper or any other porous material.

The researchers have already synthesized butyl methacrylate-based copolymers soluble in organic matter, as well as methacrylate-based dispersions, water-soluble copolymers and biocyde latexes that kill mildew. The researchers are actively investigating characteristics of these polymers, as well as their ability to penetrate into and to reinforce porous specimen made of paper, chalk, clay of different degree of baking, brick and concrete. They are working in close cooperation with restoration workshops of the Russian Federation. Some copolymers have been tested by chemists of the State Hermitage and the Vilnius restoration center, others are being tried in the State Historical Museum and in the State Tretiakov Gallery. The results are highly promising.

The authors have not used computer simulation yet, although solution of a task with such a large number of variables is exactly appropriate for computers. Computer simulation has not been performed not due to the lack of knowlegde, but because of the lack of funds: computer simulation is very expensive. Nevertheless, the researchers hope that this stage of work is still ahead.

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