An examination of the value of the re-forming technique in practice

Abstract

The varnishes of 166 paintings were examined, before and after re-forming, by means of mixtures of cyclohexane, toluene and acetone having systematically increasing solvent power. The examination proves that re-forming facilitates the solubility of aged traditional natural resin varnishes. 54% of the varnishes were removed, after re-forming, with toluene and even ‘milder’ solvents.     

The Stabilizing of Wood found in the Viking Ship of Oseberg—Part II

Abstract

Although smalt, a glass, might be expected to behave as a stable pigment, discolouration of smalt-containing paint layers has been observed. Early references from the literature are cited which mention the discolouration of smalt in oil media. Originally blue layers on paintings have changed into dull grey or greyish-green. Experiments suggest the following factors for this discolouration: low refractive index of the pigment compared with that of oil media; interaction of alkali content or cobalt content with oil and oleo-resinous media; the possibility of similar reactions with resin- or oil-resin varnishes in certain conditions. Discolouration may also occur if smalt is mixed with other pigments, or added as a drier or as an adulterant.

A proper understanding of the mechanism of the deterioration would require further research by more sophisticated methods.     

Characterization of Zinc Carboxylates in an Oil Paint Test Panel

ABSTRACT

Zinc (carboxylate) soaps, formed by reactions between zinc oxide (ZnO) and fatty acids in a drying oil, are known to cause deterioration in the paint layers of modern and contemporary oil paintings. This study investigates zinc carboxylates that developed in an oil painting test panel designed to mimic the aging and degradation encountered in actual works of art. Following accelerated and natural aging, protrusions were noted on the surface of the test panel. A large protrusion with erupted gel features was extracted from the test panel, mounted in top view, and then cut to reveal the sample's cross section. The gel features, which resulted from the unreacted oil binder's separation from the paint matrix, facilitated zinc carboxylate formation. Using reflectance µ-FTIR and SEM-EDX analysis, the morphologies and spatial distributions of zinc carboxylates within the gel regions of the protrusion were studied. A concentration gradient of zinc within the gel material was observed in the cross-sectional view, indicating patterns of zinc carboxylate formation and migration.     

Jack Chambers’ mixed media paintings from the 1960s and 1970s: Painting technique and condition

Abstract

This study describes the examination and analysis of four mixed media paintings from the 1960s and 1970s by Canadian artist Jack Chambers (1931–1978). The documentary evidence about his materials and methods is summarized and compared with the results of analysis of multilayer paint samples. The combination of Fourier transform infrared spectroscopy (FTIR) and gas chromatography-mass spectrometry (GC-MS) allowed the components of the paint media to be characterized: ortho-phthalate alkyd resins, iso-phthalate alkyd resins, drying oils, dammar, Pinaceae resin, and turpentine were identified in varying proportions. Many pigments and fillers were identified by FTIR and Raman and are enumerated. The effect that Chambers’ complex technique has had on the aging and degradation of the paintings is discussed. The severe cracking of the paint layers in one of the four paintings may be the result of a high proportion of dammar and turpentine diluent mixed with the alkyd paint and may also be related to the type of alkyd resin medium. Different history and environmental conditions may also be factors.     

Early aqueous dispersion paints: Portuguese artists’ use of polyvinyl acetate, 1960s–1990s

Abstract

The ageing of poly(vinyl acetate), PVAc, paints was assessed in works by Ângelo de Sousa and Joaquim Rodrigo. The materials and techniques of the artists were studied through interviews and by chemical analysis. They were both using PVAc in 1961, preparing their own paints by mixing commercial PVAc emulsions with selected colorants. It is shown that in most cases the emulsion employed was based on a PVAc homopolymer and that the paints are in good condition with no signs of deterioration. Finally, this study allowed a comparison to be made between paint samples aged naturally and those aged under artificial conditions. This means that these artificially aged samples may be used as reference materials for PVAc paintings. Both sets exhibit molecular infrared fingerprints that are undistinguishable from an unaged PVAc, suggesting little chemical degradation over 50 years of natural ageing.     

Directions in television and aging research

Following from a summary review of television and aging research studies, methodological difficulties of past investigations and needed directions for future mass communication and aging research are discussed.     

A Technical Analysis of Three Paintings Attributed to Jackson Pollock

Abstract

Three paintings from a group of thirty-two attributed to Jackson Pollock (1912–1956) were examined at the Harvard Art Museums. Paint samples were examined using Raman spectroscopy, scanning electron microscopy–energy dispersive X-ray spectrometry (SEM-EDX), laser desorption ionization time-of-flight mass spectroscopy (LDI-MS), Fourier transform infrared spectroscopy (FTIR), pyrolysis–gas chromatography–mass spectrometry (py-GCMS) and carbon-14 (C-14) dating. Carbon-14 dating detected no 'bomb' carbon from atmospheric atomic testing. All three paintings contained pigments and media available only after Pollock's death, including PR 254, PY151, and an emulsion copolymer of n-butyl methacrylate and iso-butyl methacrylate.     

The conservation and iconography of Viceregal paintings and sculpture: old problems and new approaches

Abstract

The reasons for the often poor condition of Viceregal paintings and sculptures are examined. The conservation of four works is described, chosen largely because they had typical problems and would benefit from recently developed techniques. The treatments were: the preliminary lining of very cupped paintings, before using moisture to stretch the original canvas and allow the paint layer to lie flat again; lining badly torn paintings on a thin, semi-rigid, transparent support and using the old stretcher, in order to preserve the structure and aesthetic impression of the painting as much as possible; masking to protect susceptible fine lines against solvent action during cleaning; blending disturbing passages of the paint layer like blanching, irreducible stains, singeing and pentimenti into the colour scheme without overpainting; repairing broken pieces of sculpture with bamboo dowels. The study is accompanied by an iconographical discussion of colonial works of art.     

CONSER VATION OF THE WOODEN ELEMENTS IN THE RENAISSANCE HOUSES OF THE PEOPLE’S REPUBLIC OF BULGARIA

Abstract

Furunori (aged paste) is a conservation material that is used for Japanese painting conservation. Furunori is a smoother and weaker adhesive than fresh paste, and it enables the surfaces to be easily peeled apart, with application of water, in a future conservation. Due to these characteristics, furunori has traditionally been used for attaching the backing paper to paintings in Japan, because it is considered that furunori causes less stress on the paintings than fresh paste. This study aims to clarify the characteristics of furunori based on chemical analysis and examination of the microorganisms involved in the early stage of furunori generation. Based on the results obtained, a polysaccharide similar to furunori was prepared.     

A note on the use of blue and green copper compounds in paintings

Abstract

Various copper compounds which were used as pigments have been identified in a study of the layer structure of paintings. These pigments were either obtained from natural minerals or were synthesized. The results of attempts to synthesize copper-based pigments by following old recipes are also presented; the man-made pigments are compared with those found in paintings and with natural copper minerals of identical composition. The historical use of synthetic copper-based pigments is discussed.     

Radiocarbon dating of canvas paintings: two case studies

Abstract

Well-cleaned canvas fibres from two oil paintings have been dated by radiocarbon. Although the dates agree with the expected ages of the paintings to a first approximation, uncertainties in the date arise from ambiguities (or ‘wiggles’) in the calibration curve. Only by introducing additional information about the paintings into the calculations can more precise results be obtained. Two paintings have been dated in this way, using the radiocarbon dating technique in conjunction with dendrochronological and art historical information.     

NOTES ON THE USE OF A VACUUM HOT-TABLE FOR TEXTILES

Abstract

A miniature low-pressure apparatus for localized treatment of paintings is described. Alternative working surfaces are available which allow heat and moisture treatment on canvas paintings without removal from their stretchers. Other applications of the apparatus are discussed.     

‘Tales of Japan’: a travelling exhibition of Japanese art from the New York Public Library

Abstract

Acrylic polymer dispersions, regularly used as artists' media or varnishes, were monitored for the development of yellow discoloration under natural aging conditions for a period of two years. Films of a number of water-based acrylic artists' media were kept under visible light of either moderate (150 lux) or low (50 lux) intensity (cycled on 10 hours per day) and were compared to films kept in dark storage, which have been observed to yellow. Results after two years show that exposure to visible light at 150 lux effectively prevented film discoloration in a number of products, and seemed at least to slow the rate of yellowing in others. Exposure to low-intensity (50 lux) lighting was found to be less effective in preventing this yellowing.     

I. Azurite and Blue Verditer

Abstract

Samples of pigments from excavated wall paintings of Vergina’s second tomb were analyzed by the non-destructive methods of X-ray fluorescence, X-ray diffraction and mineralogical microscopic examinations. The results showed that one type of blue pigment was used, the well-known Egyptian blue. The red pigments, except one which is haematite, are cinnabar (HgS), and the grey pigments are carbon. None of the black pigments contained manganese compounds.     

Investigation of acetic acid bacteria isolated from the Kitora tumulus in Japan and their involvement in the deterioration of the plaster of the mural paintings

Abstract

The Kitora tumulus, which is thought to have been built around the late seventh to early eighth century, has beautiful mural paintings which were executed directly on a very thin layer of plaster in the stone chamber. When the paintings were found, the plaster was partly detached from the stone wall and the murals were therefore considered to be likely to fall off the wall with a casual touch or stimulation. Therefore, it was decided to detach the mural paintings and to store them flat and under controlled environmental conditions. This was initiated immediately after the excavation of the tumulus in 2004. However, fungal growth and biofilm development were observed within the stone chamber during the relocation work. In 2005, small holes containing black substances were observed on certain areas of the ceiling plaster, and following investigation an acetic acid bacterium, Gluconacetobacter sp., was isolated from the black substances. The bacterium was also isolated from the ceiling, floor, and east wall in the stone chamber in 2008 after the relocation of most of the paintings had been completed. These bacteria were shown to decompose calcium carbonate (CaCO₃), one of the primary components of the plaster, and to produce organic acids such as acetic acid. Additionally, they were observed to decrease the pH of the culture media significantly in the presence of ethanol and glucose. This is the first example of the characterization of acetic acid bacteria isolated from decayed plaster paintings, and it is likely that microbes such as these bacteria have been involved in the deterioration of the plaster. Chemicals to treat microbes in the Kitora tumulus during the relocation work were selected on the basis of their antimicrobial efficacy, low potential to cause adverse effects on the paintings, and low level of toxicity to humans, depending on the condition of the plaster or stone in each area. However, some chemicals, especially ethanol, may act as a carbon source, which could encourage the growth of microbes and thereby the production of acids by the microbes when diluted to a low concentration or in a degraded state. Moreover, prior contamination by other microbial species in the form of a biofilm could also encourage the growth of the acetic acid bacteria by providing low-molecular-weight organic materials as a nutrient source.     

Book reviews

Abstract

Using written accounts of observed methods and materials of Tibetan paintings as well as examination of numerous examples, the techniques of Tibetan paintings, especially paintings on cloth, are discussed. Brief mention is made of the regional styles of Tibetan painting, since the techniques used in the production of these paintings apparently vary throughout Tibet and China. Various types of supports are mentioned and analyses of the types of cloths are given. The preparation and materials used in the ground, pigments and preliminary drawings and prints are discussed. The iconometrics of Tibetan painting are mentioned, since the total conception of the object is dependent upon them.     

The evolution of Lucio Fontana's painting materials

Abstract

The study focuses on the range of pigments and media that the Italian artist Lucio Fontana (1899–1968) employed for selected works dating between 1949 and 1968. Samples were taken from ten groups of works, all on canvas support, as well as from painting equipment that survived in the artist's former two studios. Techniques of analysis used were pyrolysis-gas chromatography–mass spectrometry for media identification, and laser desorption ionization time-of-flight mass spectrometry and Raman microspectroscopy for pigment identification. Fontana's reputation as a daring and experimental artist, best known for his group of slashed paintings called tagli, is seen to correspond with certain unusual material choices he made. The study also points to several links that exist between seemingly unrelated cycles. These links are, among others, based on experiences with in part novel media such as oil, alkyd, polyvinyl acetate, acrylic, acrylic–vinyl, and mixtures of them. With regard to pigments, the selection of samples showed that they were mostly of a synthetic organic nature.     

The conservation of wall paintings in Quito,Ecuador: two case studies

Abstract

Two projects undertaken as part of a Unesco project for the conservation of the cultural heritage of Ecuador are described. Wall paintings in the dome of the church of EI Sagrario in Quito had been damaged by watersoluble salts carried by penetrating rainwater. The dome was protected with a hydrophobic coating and allowed to dry out prior to treatment of the paintings. As part of a programme to train Ecuadorean specialists, paintings on the south wall of a cloister in the convent of San Diego were selected as a model of conservation work.     

Prediction of the relative humidity response of backboard-protected canvas paintings

Abstract

simple mathematical model is presented that predicts the decay time of the internal relative humidity (RH) of backboard-protected canvas paintings when subjected to external RH fluctuations. The model takes into account the permeance of the canvas and the hygroscopicity of the enclosed materials. Predictions from the model are tested experimentally. The wooden stretcher releases moisture more slowly than expected, providing less buffering than predicted by the model. The practical implications of these findings are discussed.     

NOTE ON THE TECHNIQUE AND CONSERVATION OF SOME THANG-KA PAINTINGS

Abstract

The article is a concise report on the art historical as well as technical aspects of thang-ka paintings. It also describes briefly the traditional methods and materials employed in the execution of these paintings. The artists’ materials described in the literature are compared with actual findings as a result of analysis of pigments, binding media and other materials involved in the execution of the thang-ka paintings. An outline of the causes of deterioration of thang-kas is also mentioned. Finally, an extensive account is given of the method of treatment carried out in the author's laboratory.