| Abstract: | SUMMARIES. This paper presents a new approach for the elimination of hydrophobic materials from the surface of wall paintings. Nanostrctured systems wth well-characterized physicochemical properties are proposed as an alternative to unsupported organic solvents for solubili:ing substances on porous painted surfaces. Due to the wide range of components that can he used in their preparation, these systems can potentially be used to remore a wide range of different types of organic materials. The results of experiments using oil-in-water microemulsions and micellar solutions as cleaning agents for wall paintings are given. The efficacy of these systems has been tested in several Italian conservation workshops for the removal of various hydrophobic materials. In particular, they have been successfully used during the conscription of the frescoes in the Loggia del Bigallo in Florence (affected by degraded natural organic materials/, and for the removal of various synthetic organic resins from the surface of the Filippo Lippi frescoes in the apse ot the Cappella Maggiore in Prat o Cathedral. Furthermore, oil-in-water microemulsious have also been shown to be effective cleaning agents tor the removal of oil- and acrylic-based paint used by vandals to deface an eighteenth-century a secco painting in the lilla del Barone in Prato. The results are supported by detailed photographic documentation and Fourier transform infrared (FTIR) spectra.
CONCLUSIONS. The experimental results indicate that both micro¬emulsions and micellar solutions are effective in the solu-bilization and removal of organic materials such as vinyl and acrylic resins from painted surfaces. This has been confirmed by FTIR spectroscopy studies. Therefore, these systems can be proposed as an alternative and inno¬vative tool tor use in art conservation. In particular, the development of these systems presents two major advantages: 1 The amount ot the organic active phase required is significantly reduced, and therefore the impact on the environment by such treatments is diminished. 2 The redistribution of solubilized materials into the porous matrix is minimized by the compartimental-ized solubilization that occurs either inside the hydro-phobic core of the droplets (microemulsions) or at the interface between the surfactant and the continu¬ous medium (microemulsions and micellar solutions). Moreover, the continuous aqueous phase constitutes a hydrophilic barrier to the penetration ot hydro-phobic materials into the support. It is also important to note that the selection criteria governing the choice of one microemulsion over another, or indeed a micellar solution, are closely associ¬ated with the chemical nature of the hydrophobic material that is to be removed and the most suitable organic solvent for its solubilization. In other words the dispersed system is developed from the outset by selecting the best solvent - for example, referring to the Teas charts [4] — and then selecting the most appropriate dispersing system (microemulsion or micellar solutions) in order to achieve the best performance. The potential availability of a very large number of these dispersed systems makes this approach very interesting and innovative since it is possible to create, on an ad hoc basis, microemulsions or micellar solutions tor the removal of a wide range of organic materials from painted surtaces. This affords the conservator a more sophisticated approach to treatment through the development of cleaning agents that are specifically tailored to suit the conservation needs of the individual object, and presents a fascinating area tor future research. |
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