The main constituents of textiles, paper and parchment are proteins and polysaccharides. These organic matters are particularly sensitive to damage such as spotting, dimensional deformations, depolymerisation, and offer a surface particularly suitable towards the deposition of various materials. In the case of the paper and parchment cleaning, traditional techniques are well known, as well as the risk to make halos and shades when using the mechanical action of a scalpel or solvent mixtures to thin the spots. For textile artefacts the need to remove dust, spots, and mud residues is a duty though this action is quite difficult with traditional methods because the dense weft and warp structure does not allow a complete cleaning, without a minor damage of the artwork. The authors set up a research program to verify the possibility and the results of an Er:YAG laser equipment, emitting at 2,940 nm, following the results achieved previously in OPD on the treatment of organic materials (LACONA IV proceedings).

The conservation of mural paintings requires a deep knowledge of the alterations caused by natural ageing, environmental agents and previous restoration treatments. All the operations concerning cleaning and consolidation of wall paintings must assure the safety of the paint layers. This is especially true the more fragile the painting technique. For example, “a secco” paintings, executed with organic binders such as tempera, oil, glue, when altered and damaged, present a very weak adhesion to the mortar underneath, and provoke detachment of paint fragments. In this circumstance it is necessary to find a feasible alternative to the usual cleaning methods (wet and mechanical ones) and a valid way to operate. Moreover, the removal of scialbo layers (a thick, pure lime layer applied on the wall painting) presents difficulties in order to preserve the integrity of the painting layers. Previous experiments carried out in Opificio with Er:YAG laser on easel painting cleaning, lead us to extend the experiments on the cleaning of mural paintings.

This chapter focuses on the use of Er:YAG laser cleaning technique for the removal of unwanted and/or degraded materials both from a large series of reference standards (overpainting, varnishes, patinas, and restoration materials) which simulate the layering of old paintings, and also examples from old paintings. A series of diagnostic controls (optical microscopy, SEM, FT-IR, GC–MS, and topographic techniques) were designed to study the effects of the laser radiation on the surface components, including morphological, optical, and chemical examination. The most significant results show that an effective thin-layer-removal of about 90% is obtained by submitting the painted surfaces to the laser exposure, while the rest of cleaning is rapidly accomplished in safety by applying mild solvents or aqueous methods. Consequently, possible interference with the original substrate can be noticeably minimized. No degradation compound induced by laser energy was formed. The laser cleaning procedure applied on an oil painting canvas “Morte di Adone” (seventeenth century), and on a panel tempera painting “San Nicola e San Giusto” of Domenico di Michelino (fifteenth century) shows that the surfaces cleaned by this system exhibit a morphology quite similar to that obtained by traditional cleaning methods.

Pyrolysis coupled with gas chromatography and mass spectrometry (PY-GC-MS) is a useful technique for rapid characterization of the organic materials used in art. In the characterization of proteinaceous binders fragments from pyrolysis are of low intensity. Milk, casein, and glue, for example, are sometimes difficult to detect. In the work discussed in this paper pyrolysis-silylation, in the presence of hexamethyldisilazane, has been used for characterization of some proteinaceous binders with the objective of distinguishing between them in real samples. Piperazine-2,5-dione derivatives have been found to be pyrolytic markers of protein in the different binders. Silylated compounds arising from pyrolysis silylation of lipids and carbohydrates have been detected in egg and milk, respectively.

This paper describes a method for the synthesis of Copper Resinate, which disappeared from artists' palettes in the eighteenth century. This was carried out by interpreting ancient recipes following a scientific approach. Its characterisation using Fourier Transform-Infrared Spectrometry and Gas Chromatography-Mass Spectrometry demonstrated that it is a mixture containing copper and oxidised abietic acids, mainly dehydroabietic and 7-oxo-dehydroabietic acids, formed during the preparation of the pigment and the curing of the paint layer. The composition of copper resinate paint layers, artificially aged by U.V. irradiation at 365 nm (UV), heating (T), and exposed to atmospheric pollutants (NOX) in a climatic chamber, was investigated. The combination of irradiation and temperature produced a change in colour along with a significant increase in the recovered amount of 7-oxo-dehydroabietic acid. The identification of copper resinate in a sample from an old painting should be related to the presence of the following resin compounds which are stable in the ageing process: dehydroabietic and 7-oxo-dehydroabietic acid pimaradienic acids. Photo-oxidation of the resin acids co-ordinated with copper seem to be the most probable decay mechanism responsible for the colour change in the pigment.

Pyrolysis-gas chromatography mass spectrometry is shown to be a rapid technique, requiring no sample work-up, for the recognition of organic materials, namely animal glue, egg yolk and glair, and linseed oil and casein, commonly used as binding media in ancient paintings. Major compounds originating from the thermal decomposition of proteins are identified by their mass spectra and have been diagnostic for glue, glair and casein. C-16, C-18 and other lower molecular weight free fatty acids are significant markers for yolk and linseed oil; however, they are not detectable in their free form when present in low quantities or as salts. In this case, the use of simultaneous pyrolysis-methylation (SPM), by addition of an aqueous solution of tetramethylammonium hydroxide to the sample, is recommended. Chromatograms of pyrolysates of binding media and of samples from original paintings are shown.