A new bio-based organogel for the removal of wax coating from indoor bronze surfaces

Abstract

In this research, we propose an advanced system for the cleaning of wax-based coatings applied on indoor bronzes. To this aim we developed a new kind of eco-friendly gel based on PHB (poly-3-hydroxybutyrate) used as thickening agent, biodiesel (BD) and dimethyl carbonate (DMC). BD is a mixture of methyl esters obtained from palm oil, which acts as cleaning agent while DMC was added as additional solvent to partially solubilize PHB and forming a gelly phase. For the first time a PHB-based gel obtained by mixing two solvents with different proprieties was proposed, expanding the range of possible formulations, that can be used according to the specific restoration purpose. After the preliminary characterization of chemical and physical properties of the gel, an ad hoc analytical protocol was implemented to evaluate both the cleaning efficiency and the release of residues on the treated surfaces. Standard samples were prepared following ancient recipes and submitted to spectroscopic and chromatographic analysis before and after the cleaning procedures. Finally, the performances of PHB-DMC/BD gel were assessed on a real case of study presenting a wax-based coating: the Pulpito della passione attributed to Donatello and dated back to 1460. In situ analysis demonstrated the high cleaning efficiency of the proposed systems also for the removal of aged coatings.

Valorization of waste waxed corrugated cardboard via pyrolysis for recovering wax

“…Additionally, two broad peaks were detected at 2 θ ≈ 18–25° and 35–45°, indicating the presence of amorphous content in the extracted wax. A comparison of diffractograms of WCCB with extracted wax suggests that the disappearance of the 004 peaks in extracted wax could be associated with the solubilizing effect of non‐polar solvent 75 . The absence of peaks at 310 and 311 in WCCB could be attributed to the effect of pyrolysis temperature.…”

“…68 The XRD ison of diffractograms of WCCB with extracted wax suggests that the disappearance of the 004 peaks in extracted wax could be associated with the solubilizing effect of non-polar solvent. 75 The absence of peaks at 310 and 311 in WCCB could be attributed to the effect of pyrolysis temperature. The diffractogram of the extracted wax is similar to that of petroleum wax.…”

Biologically Derived Gels for the Cleaning of Historical and Artistic Metal Heritage

“…Nowadays organogels as cleaning systems have been explored mostly on paintings and graphic documents, being multi-component artifacts and strongly sensitive to solvents [81][82][83]. On the contrary, in the literature rare is evidence of their application in the branch of metal conservation [84,85]. The main critical aspect of such implementation appears to be the rigidity of such systems.…”

“…From the chemical point of view, biodiesel is a blend of alkyl esters and long-chain fatty acids [84]: this makes it an appropriate solvent for non-polar substances.…”

Chemistry for cultural heritage: connecting past and future

“…New studies in metals and paintings cleaning are also reported: Baij et al [21] contributed to a better understanding of the impact of different methods of solvent application on oil paintings and highlighted important differences between these methods; Moretti et al [22] aimed at developing an efficient methodology for in situ assessing painting surfaces after the laser cleaning using optical coherence tomography (OCT) and reflection FT-IR spectroscopy complemented with laser induced fluorescence (LIF) spectroscopic measurements; Yiming et al [23] developed a new kind of eco-friendly gel based on PHB (poly-3-hydroxybutyrate), biodiesel (BD) and dimethyl carbonate (DMC) for the cleaning of wax-based coatings applied on indoor bronzes.…”