Showing papers in "Studies in Conservation in 1974"

La ‘maladie verte’ de lascaux

Abstract: Decouverte en 1940, la Grotte de Lascaux revet un interet archeologique mondial en raison du nombre tres important de peintures et de gravures qu’elle renferme et qui sont dans un etat de conservation remarquable. Tres petite, son volume total n’excede pas 1 500 metrescubes. Des qu’elle fut ouverte au public, apres les travaux d’amenagement, environ 120 000 visiteurs y passaient chaque annee. Apportant des poussieres des microorganismes par leurs vetements, de la vapeur d’eau, du gaz carbonique, des matieres organiques par leur respiration et leur sueur, ils perturberent gravement l’equilibre interne de la Grotte et y creerent un climat particulierement favorable a la multiplication de vegetaux et en particulier d’Algues heterotrophes. Les premieres apparurent en 1960, se multiplierent tres rapidement et commencerent a attaquer les peintures. C’est ce qu’on a appele la ‘Maladie Verte’. Des microbiologistes qualifies furent charges d’etudier cette maladie et d’y trouver un remede, ce qui fut fait r...

Calcium carbonate whites

Abstract: Topics discussed include: calcite, marble, and limestone; chalk; prep aration; history of use; synthetic or precipitated calcium carbonate; lime white; shell white; coral; color; optical properties of calcite; physical properties; chemical properties; permanance and compatibility; purity of composition; identification; particle characteristics; microchemical tests; emission spectrographic analysis, x-ray diffraction, x-ray spectrometric and electron probe analysis; infra-red absorption spectroscopy, neutron activation analysis and radiography. Extensive micrographic illustration, charts and tables are included. Occurrences of chalk on paintings are given in several tables. For example, Joyce Plesters reports occurrences of chalk in paintings of European schools examined in the scientiflc department of the National Gallery in London.

Rationale of the barium hydroxide-urea treatment of decayed stone

Abstract: Optical and electron-beam microprobe examination of pairs of calcite crystals, mounted approximately 50 microns apart and then immersed for various times in solutions containing a barium compound and urea, showed that these crystals were cemented together by the formation of an adherent bond between the calcite substrate and the witherite filling the void space between the crystals. The bonding material was found to be composed of a series of solid solutions of barium calcium carbonate, high in calcium content at the original surface and increasing in barium content as the distance from the original crystal surface increased. The relatively rapid rate of reaction suggests that the formation of the solid solutions proceeds by a co-precipitation mechanism. The formation of the solid solutions is thought to occur most readily in pores and cracks where the calcium ions generated by the dissolution of calcite cannot readily diffuse into the bulk solution. Application of the barium hydroxide-urea treatm...

X-Ray Analysis of Greek Bronze Age Pigments from Mycenae

Abstract: Wall-paintings of great artistic value decorated the palaces and great houses of flourishing cities of Greece during the Bronze Age. Several scientists have already given related reports of historical and archaeological interest [1-3], but little information exists in literature about the nature of the pigments used by Greek painters of this era [4]. Thus a systematic study of these pigments by means of modern methods of analysis would be of significant value.

A simple method for the identification of indigo

Abstract: A quick and simple chemical identification method which can be con-tinued by further chromatographic analysis is described. Indigo and other dyestuffs can be analyzed in the same sample, and the method can be used for textiles as well as for pigments in paint layers. -- AATA

A Note on the Use of an Improved Infrared Vidicon for Reflectography of Paintings

Abstract: In infrared reflectography of paintings infrared-to-visible image translation systems are used, operating around 2.0 microns; paint layers become most transparent in that spectral region to detect an underdrawing beneath. Earlier work was successfully carried out with a Barnes Infrared Camera equipped with a lead sulphide detector peaked at about 2.0 microns [1]. Later an infrared vidicon was used manufactured by Heimann PTW in a television system [2]. This vidicon is not ideal because it is not peaked at 2.0 microns-in fact its responsivity extends only to about 1.8 microns. In practice, however, reflectograms were often comparable with those obtained with the earlier Barnes system, although penetration of malachite-containing paint was inferior and interference of overlying paint layers more pronounced. Hori et al. have reported the development of an infrared vidicon with a multi-layer PbO-PbS-sensitive target showing a very short time-lag, a higher resolution and a wavelength response up to 2.0 microns [3]. This vidicon would have been preferable but it is not commercially available. Recently, however, an infrared vidicon manufactured by Hamamatsu Inc. [4] has been made commercially available with a wavelength response up to 2.4 microns. This vidicon has indeed the responsivity required for optimal infrared reflectography; in addition it can be estimated that its signal current when using a 0.8 micron cut-on 100

Efficiency of epoxy resins as stone preservatives

Abstract: Earlier studies on stone conservation by Gauri [1] and Gauri et al. [2, 3] were concerned with impregnation techniques and with the changes rendered in the physical and chemical properties of stone as a result of impregnation treatments. While studying the reactivity of test specimens in dynamic, SO,-enriched atmospheres, Gauri et al. [3] found that certain epoxy resins provided more protection than other epoxy resins. They had also found that certain epoxy resins even increased the reactivity rather than providing protection to the treated stone. Specifically, the reactivity of specimens treated with Epi-Rez* 510 was less than the reactivity of the specimens treated with Epi-Rez 504, and certain specimens having thick coatings of Epi-Rez 504 were more reactive than the controls. One of the causes of this enhanced reactivity was thought to be the occurrence of perforations [3; Figs. 6, 7] resulting from frothing of the resin during polymerization and the escape of the solventvapor from deeper layers of treated stone. One of the purposes of this note is to present an additional, and certainly more effective, cause for such increased reactions. Another purpose of this note is to emphasize the need of laboratory testing of preservative treatments in concentrated atmospheres for accelerated weathering. The appraisal of this additional cause to enhance calcite-SO, reactivity has emerged from considerations concerning the chemistry of the resins applied in our treatments. Epi-Rez 510 is a bisphenol-A diglycidal ether. Epi-Rez 504 which, rather than providing protection, increased the reactions of treated specimens as compared with the untreated, is a mixture of Epi-Rez 510 and Epi-Rez 502. Epi-Rez 502 is an aliphatic diglycidal ether. To establish that it is the occurrence of an aliphatic group in the epoxy chain that causes an excessive

An improved method for the thin-layer chromatography of media in tempera paintings*

Abstract: Thin-layer chromatography of Dansyl amino acids derivatives permits the improvement of the limits of detection of protein media in paintings. These derivatives can be detected in very small concentrations by their fluorescence under ultraviolet light. The procedure of identification is described and some examples are given.

Consolidation of painted wooden artifacts

Abstract: Wood, particularly in the presence of excessive moisture, deteriorates due to action of biological agents and sunlight. Decay manifests itself not only in impairment of physical strength but also in discoloration. Protection of the paint during consolidation by impregnation and polymerization, albeit difficult, is possible. Details of a home-built 23 cm-diameter and 48 cm-long chamber for vacuum impregnation are given. The permeating methylmethacrylate monomer solution used with good results contained bis-4-t-butylcyclohexyl peroxidicarbonate as catalyst, and pyridine as activator in addition to methylmethacrylate polymer, which reduced the rate of heat generation by the reaction. Polymerization induced by gamma irradiation also yielded satisfactory results. Case histories of three artifacts are described.

Properties and preservation of ethnographical semi-tanned leather

Abstract: In contrast to fully tanned leather, that used by the Canadian Indians and Eskimos has poor durability. When stored under less than ideal conditions it becomes stiff and brittle, and restoration of such artifacts presents problems. The methods used for sound leather, such as fat liquoring or staking, cannot be used once the skin has deteriorated. A method used successfully is described. It consists of soaking the artifact in water to gain pliability and then replacing the water with organic liquid in order to avoid shrinkage on drying. Flexibility is preserved by permeation with an emulsion containing a stabilized olein soap, neat’s-foot oil and ethyl alcohol. Gut-skin may be treated by a modification of this emulsion. Fur poses a lesser problem because the skin is thin and can easily be permeated with an aqueous emulsion of sulfited sperm oil. Several examples of restoration are given.

Decay of pietra serena and pietraforte, florentine building stones: petrographic observations

Abstract: Pietra Serena and Pietraforte, the two stones most frequently used in Florentine architecture, have been considered in this study. Through mineralogical-petrographical study and by determining the physical properties of these materials it has been possible to show clearly that the principal factors of their decay are seepage of water and changes of temperature. The simultaneous appearance of these two factors seems to induce the decay with different characteristics in the two stones. Gypsum, thought by some authors to be one of the main factors in the decay of stones, has been detected on materials already deteriorated; it is a product of decay apparently brought on by natural change, and may take part in a process which accelerates the decay.

A nineteenth - century collection of pigments and painting materials

Abstract: Fifty-six samples of an historic pigment collection were examined. A great number of the pigments are standard colours of the early nineteenth century, such as emerald green, chrome green, Prussian blue, Naples yellow, mummy, and sepia. Many pigments are extended with inert fillers, mainly barytes and gypsum. However some rare or unusual pigments were also detected. Among these are orange antimony sulphide and a green artificial basic copper sulphate of brochantite structure.

The pigments of the swiss nineteenth-century painter arnold böcklin

Abstract: Seventy samples of a pigment collection from the heritage of the Swiss nineteenth-century painter Arnold Bocklin were examined. The results were compared with the pigments in 15 Bocklin paintings identified by Hermann Kuhn. Bocklin’s palette includes a wide range of different pigments; most of them are typical nineteenth-century products. An interesting feature in Bocklin’s painting techniques is the incidental use of historic pigments such as azurite, smalt, red lead, and copper resinate.

The Conservation of the Wooden Writing-Tablets from Vindolanda Roman Fort, Northumberland

Abstract: In April 1973 several fragments of waterlogged wooden writing-tablets, which had been excavated at Vindolanda Roman Fort [1], were brought to the British Museum Research Laboratory for conservation. The tablets were of two types, several of them being flat tablets of wood in which a recess had been cut to take a wax writing-surface, while the majority of them were much thinner sheets of wood (c. 2 mm thick) often having traces of writing in a black ink on their surface. The excavators had reported that this writing was more clearly visible when freshly exposed, but that it faded rapidly upon exposure to light and the atmosphere. Several of the fragments of recessed tablets were splintered at their broken edges, and the wood was fairly soft. Many of the thin tablets were broken into small fragments. The wood was reasonably soft and easily split if handled without great care. Some of the tablets had warped and could not be straightened without splitting the wood. For transport to the Research Laboratory the tablets were packed in tissue paper which had been soaked in water containing a fungicide. Upon arrival they were unpacked, any remaining dirt was washed off the surface, and they were then placed in distilled water. As soon as possible after unpacking, the tablets were photographed on infrared film to ensure that the inscriptions should be recorded. Figure la illustrates one of the tablets at this stage. They were then examined under ultraviolet light, but the ink did not fluoresce, which suggests that it was probably a suspension of carbon in a suitable binding medium.

An examination of particle size distributions of azurite and natural ultramarine in some early netherlandish paintings

Abstract: Subjects discussed include: the use of paint cross-sections, choice of pigments, particle size measurements, discussion of the location and dispersion of the distributions, discussion of the log-normal probability graphs, statistical testing for differences between the particle size dis-tributions, and measurement of the pigment volume concentration. Some statistically significant differences in pigment particle size distributions from various paintings have been shown.

The conservation of a preserved human head

Abstract: Large ethnographical collections sometimes contain examples of preserved human heads. There are those from the Maori of New Zealand, the well-known Jivaro Indian shrunken heads, and others from Papua-New Guinea. The article describes the preservation process as practised in Western Papua by the tribal craftsman, and then the problems of conservation in the museum laboratory. The latter include the cleaning of the skin, and the painted areas of the face, with the non-ionic surface-active agent Lissapol N in distilled water, followed by consolidation of the painted surface with an application of 2 % soluble nylon in industrial methylated spirit. Clay and fibre within the head were consolidated with a 5 % solution of the polymethacrylic ester Bedacryl 122X (I.C.I.) in xylene; and the fibre ear ornaments, after cleaning with Lissapol N, were consolidated with a 5 % solution of soluble nylon in industrial methylated spirit. The specimen was fitted with a specially made polythene cover, and stored in an...

The restoration of thin metal vessels using glass-fibre and polyester resin

Abstract: The restoration of thin metal vessels using glass-fibre matting and polyester resin is described. The method is compared with the use of more traditional materials and with the application of resins using different techniques. A series of photographs illustrates the practical details of the method.

Comportement des reliures en cuir soumises a differents traitements de desinfection

Abstract: Abstrait—Des peaux de veau, chevre et mouton tannees vegetalement ont ete soumises a trois traitements de desinfection (l'oxyde d'ethylene, le formaldehyde et le lindane) dont l'innocuite vis-a-vis des papiers a ete prealablement demontree. L'experience a ete menee parallelement sur des peaux vierges et sur des peaux vieillies artificiellement. Differentes tests de resistance mecanique et chimique ont ete mis au point pour controler le comportement des cuirs: resistance a la dechirure, a la traction, a l'eclatement pour les examens mecaniques; taux d'humidite, de matieres grasses et d'azote soluble, mesure du pH pour les examens chimiques. Les essais ont ete effectues sur des eprouvettes de cuir decoupees suivant la technique 'des carres latins' en utilisant toute la surface de la peau, a l'exclusion de la tete et des pattes. Les resultats des essais mecaniques ont presente une telle dispersion qu'il a ete necessaire de faire appel a l'analyse statistique pour les interpreter. Afin de suivre le comportement dans le temps des cuirs traites, nous avons selectionne deux methodes de vieillissement accelere: la chaleur seche a 100° C et l'oxydation par le peroxyde d'hydrogene en milieu sulfurique. Dans l'ensemble, il apparait que les trois traitements de desinfection n'ont aucune action nefaste sur les peaux de veau. Par contre, les traitements par le formaldehyde et le lindane semblent avoir diminuer la resistance physique des peaux de chevre et de mouton.