Partially fluorinated derivatives as a powerful tool for the restoration of blanched easel paintings

The use of specific coatings has considerable importance in the field of cultural heritage conservation. The blanching of easel paintings is a worrying phenomenon induced by excessive humidity and porous structures, often obscuring the image beneath a white haze. The research available in the literature describing solutions to solve this problem is extremely limited. In this research, new oligoamides containing hydroxyl and/or amino groups, i.e. , partially fluorinated oligodiethylene succinamide- l -tartaramide ( DSTF ) and oligodiethylene succinamide ( DSF ), were designed to give high affinity with the polar components present in paint films through non-covalent interactions, and have reduced environmental impact compared to the previously proposed perfluoroamide ( DC6G900 ). These innovative products represent one of the few solutions proposed for this area of application. Their syntheses were carried out via condensation and subsequently ring-opening reaction of the short-fluorinated epoxy compound, 3-perfluorohexyl-1,2-epoxypropane ( EC6F). The short-fluorinated chain has a dual effect; it improves surface performance by lowering surface tension while simultaneously reducing environmental impact compared to the perfluoro source previously used. The performance of the two new fluorinated oligoamides ( DSTF , DSF ) on blanched easel paintings was investigated through a series of tests, from the macroscopic to the microscopic scale. The new fluorinated oligoamides dramatically decreased the luminance value (almost restoring the value of the un-blanched sample) in comparison with the other tested compounds ( ESTF , ESF , DF and DC6G900 as a reference). This result is ascribed to the ability of the compounds to fill the pores of the blanched surfaces, as demonstrated by the morphological study using a Field emission gun - Scanning electron microscopy. In addition, preliminary investigations showed that all the tested compounds, can be removed from the treated mock-ups using 2-propanol or 2,2,2-trifluoroethanol, giving promising results concerning the removal of the restoration treatments. • New partially fluorinated oligoamides easy synthesized by two steps reaction • The new oligoamides have proven to be effective for blanched paintings restoration • The new oligoamides have reduced environmental impact compared to perfluoro compounds • FEG-SEM study proved their ability to fill the pores that cause the blanching effect