The Green Attitude in Art Conservation: Polyhydroxybutyrate–based Gels for the Cleaning of Oil Paintings

Abstract

Fully biodegradable novel bio‐based organogels were developed for removing aged protective films from the surfaces of paintings, aiming at providing effective cleaning tools, easily controllable by reducing the solvent permeation into underlying paint layers and not dangerous for human health and the environment. The gels were based on poly‐3‐hydroxybutyrate (PHB) as gelling agent, γ‐valerolactone (GVL) as solvent and triethyl citrate (TEC) as plasticizer. PHB‐gels were able to completely remove protective varnishes on real oil paintings, without affecting the pictorial layer and leaving negligible residues after the application. Moreover, the gels showed good mechanical and handling properties, they were fully composed by non‐toxic ingredients and resulted readily biodegradable in water, therefore easily disposable after the use.

Sustainability in art conservation: a novel bio-based organogel for the cleaning of water sensitive works of art

“…A full analytical characterization of gels similar to the one tested in this research and the biodegradability test of their components were reported by Samorì and co-workers [30]. The results demonstred that a thermoreversible physical gel was formed, exploiting the ability of the polymer to crystallize and swell in the presence of appropriate solvents such as GVL.…”

“…Superficial analysis on mock ups were acquired in the range of 4000-675 cm −1 on untreated and treated areas with an ATR equipped with a germanium crystal, a spectral resolution of 4 cm −1 and an optical aperture of 200 × 200 μm 2 . The solvent fraction retained by the paint layer after cleaning was determined by gas chromatographymass spectrometry analysis using headspace solid phase micro extraction (HS-SPME) sampling method [30]. A Carboxen/Polydimethylsiloxane fibre was directly exposed in the headspace of sealed vials containing the sample fragment collected from treated areas at fixed times (1 h, 24 h, and 3 days after cleaning).…”

“…Within this scenario, we have recently prepared novel gel systems based on two or three bio-based components: polyhydroxybutyrate (PHB) a homopolymer belonging to the polyhydroxyalkanoates (PHA) family, γ-valerolactone (GVL) as organic solvent; in cases, triethyl citrate (TEC) was added as plasticizer [30]. These PHB-GVL or PHB-GVL-TEC gels have been proved to be thermoreversible and physically bonded by weak interactions.…”

“…These PHB-GVL or PHB-GVL-TEC gels have been proved to be thermoreversible and physically bonded by weak interactions. Moreover, since it was observed that the stiffness of these gels made them less prone to stick to the surface, they have been successfully applied for the removal of terpenic resins from oily paintings without leaving polymer residues after cleaning [30].…”

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

“…To introduce powerful and sustainable alternatives for cleaning artworks, we have recently proposed new biocompatible cleaning systems for paintings based on the use of fully green components [20,21]. In particular, in the previous researches we have demonstrated the efficiency of poly-3-hydroxybutyrate (PHB)-based gels with γ-valerolactone (GVL) as solvent, for the removal of terpenic and synthetic varnishes from oil and water sensitive egg tempera paintings [20,21].…”