An in-depth study on the agar gel effectiveness for built heritage cleaning

Bertasa, Moira; Canevali, Carmen; Sansonetti, Antonio; Lazzari, Massimo; Malandrino, Mery; Simonutti, Roberto; Scalarone, Dominique Maria

doi:10.1016/j.culher.2020.10.007

Cited by 19 publications

(15 citation statements)

References 36 publications

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“…This result shows that all the studied gels coordinate Cu(II) centres. It was reported that agar gels also coordinate copper centres [ 5 , 7 , 10 , 11 , 12 ].…”

Section: Resultsmentioning

confidence: 99%

“…The cleaning issue of removing copper stains from artwork surfaces with agar gels has been recently studied on marble laboratory specimens that were stained with brochantite in well-controlled and reproducible conditions [ 5 , 7 , 8 , 9 , 10 , 11 ]. Brochantite, CuSO 4 3 Cu(OH) 2 , is one of the most frequently occurring compounds in outdoor bronze corrosion patinas.…”

Section: Introductionmentioning

confidence: 99%

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Optimized Semi-Interpenetrated p(HEMA)/PVP Hydrogels for Artistic Surface Cleaning

Tamburini

Canevali

Ferrario³

et al. 2022

Materials

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The synthesis of hydrogels that are based on poly-hydroxyethyl methacrylate, p(HEMA), network semi-interpenetrated with linear polyvinylpyrrolidone (PVP) was optimized in order to allow both a fast preparation and a high cleaning effectiveness of artistic surfaces. For this purpose, the synthesis parameters of the gel with PVP having a high molecular weight (1300 kDa) that were reported in the literature, were modified in terms of temperature, time, and crosslinker amount. In addition, the gel composition was modified by using PVP with different molecular weights, by changing the initiator and by adding maleic anhydride. The modified gels were characterized in terms of equilibrium water content (EWC), water uptake, conversion grade, and thermal properties by differential scanning calorimetry (DSC). The cleaning effectiveness of the gels was studied through the removal of copper salts from laboratory-stained specimens. Cleaning materials were characterized by electron paramagnetic resonance (EPR) spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy, and inductively-coupled plasma-mass spectrometry (ICP-MS). Cleaning was assessed on marble specimens by color variation measurements. The gel synthesis is accelerated by using PVP 360 kDa. The addition of maleic anhydride in the p(HEMA)/PVP network allows the most effective removal of copper salt deposits from marble since it acts as a chelator towards copper ions.

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“…This result shows that all the studied gels coordinate Cu(II) centres. It was reported that agar gels also coordinate copper centres [ 5 , 7 , 10 , 11 , 12 ].…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Optimized Semi-Interpenetrated p(HEMA)/PVP Hydrogels for Artistic Surface Cleaning

Tamburini

Canevali

Ferrario³

et al. 2022

Materials

Self Cite

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“…These gels are called peelable gels [ 13 ]. It was shown that the agar concentration strongly influences the water state within the gel network: agar at 1% wt releases far more water than gels at 3% and 5% wt, acting as a “free water reservoir” [ 14 ]. Conservators can adapt the rigidity of the gel film to suit the surface to be treated and adapt its sensitivity to water.…”

Section: Introductionmentioning

confidence: 99%

The Use of Hydrogels in the Treatment of Metal Cultural Heritage Objects

Guilminot

2023

Gels

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Currently gels are widely used in the restoration of paintings, graphic arts, stuccowork and stonework, but their use in metal restoration is less widespread. In this study, several polysaccharide-based hydrogels (agar, gellan and xanthan gum) were selected for use in metal treatments. The use of hydrogels allows to localize a chemical or electrochemical treatment. This paper presents several examples of treatment of metal objects of cultural heritage, i.e., historical or archaeological objects. The advantages, disadvantages and limits of hydrogel treatments are discussed. The best results are obtained for the cleaning of copper alloys via associating an agar gel with a chelating agent (EDTA (ethylenediaminetetraacetic acid) or TAC (tri-ammonium citrate)). The hot application allows to obtain a peelable gel, particularly adapted for historical objects. Electrochemical treatments using hydrogels have been successful for the cleaning of silver and for the dechlorination of ferrous or copper alloys. The use of hydrogels for the cleaning of painted aluminum alloys is possible but it has to be coupled with mechanical cleaning. However, for the cleaning of archaeological lead, the cleaning using hydrogels was not very effective. This paper shows the new possibilities of using hydrogels for the treatment of metal cultural heritage objects: agar is the most promising hydrogel.

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“…Chelating agents have already been successfully used in aqueous solution [8] and in hydrogels (from now on termed gels) [5,12]. Chelating agents are also used for the removal of newly formed calcium compounds, such as black crusts mainly composed of gypsum and calcite, and white calcite thin layers or encrustations [13].…”

Section: Introductionmentioning

confidence: 99%

Optimization of Copper Stain Removal from Marble through the Formation of Cu(II) Complexes in Agar Gels

Sansonetti

Bertasa

Corti

et al. 2021

Gels

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Copper complexes with different ligands (ethylenediaminetetraacetic acid, EDTA, ammonium citrate tribasic, TAC, and alanine, ALA) were studied in aqueous solutions and hydrogels with the aim of setting the optimal conditions for copper stain removal from marble by agar gels, with damage minimization. The stoichiometry and stability of copper complexes were monitored by ultraviolet-visible (UV-Vis) spectroscopy and the symmetry of Cu(II) centers in the different gel formulations was studied by electron paramagnetic resonance (EPR) spectroscopy. Cleaning effectiveness in optimized conditions was verified on marble laboratory specimens through color variations and by determining copper on gels by inductively coupled plasma-mass spectrometry (ICP-MS). Two copper complexes with TAC were identified, one having the known stoichiometry 1:1, and the other 1:2, Cu(TAC)2, never observed before. The stability of all the complexes at different pH was observed to increase with pH. At pH 10.0, the gel’s effectiveness in removing copper salts from marble was the highest in the presence of ALA, followed by EDTA, TAC, and pure agar gel. Limited damage to the marble surface was observed when gels with added EDTA and TAC were employed, whereas agar gel with ALA was determined to be the most efficient and safe cleaning material.

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An in-depth study on the agar gel effectiveness for built heritage cleaning

Cited by 19 publications

References 36 publications

Optimized Semi-Interpenetrated p(HEMA)/PVP Hydrogels for Artistic Surface Cleaning

Optimized Semi-Interpenetrated p(HEMA)/PVP Hydrogels for Artistic Surface Cleaning

The Use of Hydrogels in the Treatment of Metal Cultural Heritage Objects

Optimization of Copper Stain Removal from Marble through the Formation of Cu(II) Complexes in Agar Gels

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