Natural based products for cleaning copper and copper alloys artefacts

Abstract

Copper alloys objects can deteriorate their conservation state through irreversible corrosion. Hence, there is need to block the corrosion action with a suitable cleaning and conservation process to avoid further degradation processes without changing its morphological aspect. In this study, six natural based chelators were tested for cleaning copper artefacts exposed to atmospheric environment in polluted areas. The study considered four amino acids, a glucoheptonate (CSA) and an industrial green chelator (GLDA). The effectiveness was tested on corrosion copper compounds and on laboratory corroded copper sheets. Finally, the cleaning efficacy was tested on four Roman coins and a modern copper painting. To define the cleaning efficacy, surface analytical investigations have been carried out by means ICP-OES, UV-VIS, µ-Raman, spectro-colorimetry, XRD and FTIR. Among the amino acids, alanine was the most effective, showing unalteration of the noble patina and a good effective copper recovery from corrosion patinas.

Multianalytical Non-Invasive Characterization of ‘Mater Boni Consilii’ Iconography Oil Painting

“…The characteristic absorbances of natural resin were clearly distinguished: bands at 2917 and 2848 cm −1 can generally be attributed to the C-H stretching; the band centred at ~1701 cm −1 can be related to C=O stretching of carboxylic group of fatty acid and esters; the band at ~1460 cm −1 is related to the bending of the CH 2 groups and the asymmetric bending of the CH 3 groups; the band at 1653 cm −1 is due to C=C stretching; the band at ~1230 cm −1 is related to C-O stretching; and the band at ~3410 cm −1 is due to O-H stretching [8,14,18,[30][31][32][33][34][35][36][37]. According to the literature [8,14,18,[30][31][32][33][34], we can hypothesize the presence of shellac, which is a sesquiterpenic resin of animal origin that is secreted by an insect (Laccifer lacca) that infests the trees on which the resin is deposited. Historically speaking, shellac was mainly used not only for wooden furniture, but also as a varnish for paintings, although this application remained unknown in Europe until the 16th century [30].…”

“…In order to achieve this goal, the first analytical approach used multispectral analysis (in the UV, visible, and infrared ranges), to distinguish the different materials comprising the painting. Ultraviolet observation and digital image acquisition allowed for identification of old and recent paint layers, overpainting, later additions, and retouches, consequently distinguishing the original from subsequent pigments and dyes, depending on the different intensities and shades of fluorescence [4][5][6][7][8]. The IR reflectography investigated the central layers of the painting; due to the different absorbing properties of the constitutive materials, the technique revealed the artist's working methods, showing the presence of a preparatory drawing, pentimenti, and retouches [4,[7][8][9][10].…”

“…Ultraviolet observation and digital image acquisition allowed for identification of old and recent paint layers, overpainting, later additions, and retouches, consequently distinguishing the original from subsequent pigments and dyes, depending on the different intensities and shades of fluorescence [4][5][6][7][8]. The IR reflectography investigated the central layers of the painting; due to the different absorbing properties of the constitutive materials, the technique revealed the artist's working methods, showing the presence of a preparatory drawing, pentimenti, and retouches [4,[7][8][9][10]. The second approach involved the use of X-ray fluorescence (XRF), a non-invasive technique which is able to pinpoint the elementary and qualitative composition of the employed pigments, which in turn provides useful information regarding the authenticity and indirect dating of the painting, since the periods of diffusion of certain pigments in the art market, are currently chronologically categorized [9,11,12].…”

Marble Chromatic Alteration Study Using Non-Invasive Analytical Techniques and Evaluation of the Most Suitable Cleaning Treatment: The Case of a Bust Representing Queen Margherita di Savoia at the U.S. Embassy in Rome

“…For this reason, a 5% disodium EDTA solution in water was applied [31,32]. GLDA was prepared as in Macchia et al [33] at 5% concentration, and brought to pH 9 with acetic acid. Deionized water and alkoxide surfactant were directly suspended in cellulose pulp.…”

New Chemical Systems for the Removal of Calcareous Encrustations on Monumental Fountains: A Case Study of the Nymphaeum of Cerriglio

“…However, Ethylenediaminetetraacetic acid (EDTA) is widely used in several applications, and its persistence in aquatic systems is leading to serious environmental consequences. GLDA salts are biodegradable candidates that can replace EDTA [30,31]. They showed a strong capability of chelating calcium ions at pH values in a certain range [32,33].…”