The varnished truth: The recipes and reality of tintype coatings

The most popular photographic technique in the USA between 1856 and 1900 was the tintype, with millions of these objects created by photographers in established studios, by itinerant artists in portable workshops, and by amateurs working from ‘how-to’ manuals and journal articles. Whereas the fundamentals for this photographic process (collodion binder on a japanned metal support) were largely invariant, historical documents recommended a wide variety of protective varnish materials. A collection of 221 tintypes was analyzed using pyrolysis gas chromatography-mass spectrometry (py-GC-MS) to compare the components of actual tintype varnishes with recipes from the historical literature. Several resins in published tintype varnish recipes, including mastic, copal, and amber, are entirely absent from this collection and only five constituents – shellac, Pinaceae resin (Canada balsam or colophony), dammar, sandarac, and camphor – are detected alone or in combination. Each detected resin appears in historical recipes, but just 24% of the samples have varnish layer constituents consistent with published tintype varnish recipes. Forty-four percent of the tintypes have varnish constituents consistent with formulations recommended for other collodion images, but the varnishes of the remaining samples have no direct literature equivalents. The preponderance of shellac- and Pinaceae-based varnishes suggests that these correspond to inexpensive commercial varnishes, but tintypists may have developed their own preferred mixtures or simply used what was at hand. This first in-depth technical analysis of tintype materials suggests that the cheapest and most readily available materials were employed in the varnishing process and that the artists were not bound by literature recommendations.     

Review on the characterisation of ancient stringed musical instruments varnishes and implementation of an analytical strategy

For the last 60 years, varnishes of ancient musical instruments, particularly stringed instruments of the violin family dating 17th and 18th centuries, have been analysed to establish their chemical composition and multi-layered structure. The objective was to rediscover the technology for making the varnish of esteemed Italian violins and to reconstitute it. This paper reviews the physico-chemical studies published on such varnishes and also focuses on a research project carried out since 2002 at the Musée de la musique in Paris. It aims to apply in a comprehensive way different non-destructive or micro destructive methods (Py-GC/MS, IR microscopy, SEM/EDX, EDXRF, synchrotron radiation-based techniques, …) to the study of a large and representative number of ancient varnished musical instruments from a museum collection.     

Ontology-based shape-grammar schema for classification of caravanserais: a specific corpus of Iranian Safavid and Ghajar open, on-route samples

As part of research in progress on the study and design of an ontology knowledge model, this paper focuses on development of a shape-grammar schema for extracting attributes of spatial organization of a subset of cultural heritage relics, namely, caravanserais, from a selected corpus with a common architectural language of design. First, shape-grammar rules for classification of caravanserais of the selected corpus are developed and are represented in drawing by using Auto CAD tool. Shape rules as a natural-language equivalent are then devised by describing design functions and clarifying the topology of shapes. Based on these shape rules in given text, the hierarchy of a shape-grammar schema in the Protégé knowledge representation tool is designed, and each shape rule is defined as an interconnecting individual (or instance) in OWL language. This schema will enable us to extract computer-based semantics of shape-grammar rules. To illustrate this innovative approach, a selected corpus was classified by using the shape-grammar schema with the support of knowledge extraction tools.     

Aging and yellowing of triterpenoid resin varnishes – Influence of aging conditions and resin composition

The aging of natural triterpenoid resins used as varnishes on paintings is still insufficiently understood. Although progress has been made, questions concerning the aging pathways in light vs. darkness, or the correlation of oxidation with yellowing, remain open. The influence of aging conditions, primarily the amount of light, but also resin composition, on the aging process were investigated. The aging reactions are followed using a variety of mass spectrometric and spectroscopic techniques. Aging processes in dammar and mastic varnishes are shown to be more dynamic and extensive than had generally been believed. In unaged bulk resins, large quantities of radicals develop within weeks after application as a varnish, due to the greatly increased surface-to-volume ratio. This is true for all aging conditions, including aging in darkness, and is accompanied by considerable oxidation as well. After a few months, most of the initial triterpenoids are oxidized. Natural aging in light and darkness leads to the same main aging products. All these findings point to the conclusion that aging largely proceeds by the same pathways in both light and darkness, mainly autoxidation. Without light, enough radicals are formed to maintain extensive autoxidation, although more slowly. Thus, differences between light and dark aging mechanisms are much smaller than often believed. In mastic, the absence of the polymeric constituents is found to enhance oxidation, but reduce yellowing. It appears that the polymer acts as a natural radical stabilizer, favoring the pronounced intrinsic yellowing tendency of mastic. The manipulation of resin composition might lead to improved aging properties of triterpenoid resin varnishes.     

Review of several optical non-destructive analyses of an easel painting. Complementarity and crosschecking of the results

Five optical analyses of a given work of art are presented, using multispectral imaging, optical coherence tomography, goniophometry, UV-fluorescence emission spectroscopy and diffuse reflectance spectroscopy. All these methods are non-destructive, contactless, and implementable in situ. They all lead to results in quasi-real time. The multispectral camera allows imaging of the whole painting with very high definition and recording of 240 millions of spectra. Optical coherence tomography allows local 2D and 3D imaging with in-face and in depth stratigraphies inside the painting with a micrometric accuracy. It allows the evaluation of the pigment volume concentration inside a layer, the measurement of the thickness of one or two varnish layers, the detection and measurements of gaps inside the paint layer, the depth of varnish micro-cracks. Goniophotometry allows the measurement of the upper surface state of the painting in different locations, by quantifying the mean slope of the facets making up the surface. UV-fluorescence emission spectroscopy allows the identification of the resin, the binder and the ageing state of varnishes by use of databases of reference varnishes. Diffuse reflectance spectroscopy leads to pigment, pigment mixture and dye identifications again by use of databases. The three last methods are implemented with the same portable multi-function instrument. It allows time saving, locations on request in front of the artwork and easy use by non-scientists. Each instrument is described with its protocol and accuracy. The studied painting is a portrait of a lady painted by the Austrian artist Franz Strotszberg, chosen for its several restorations. The five kinds of results are successively detailed, analysed and compared between themselves. It is shown that the different results are complementary and their crosschecking brings thorough information. For example, the shape of the network of varnish micro-cracks detected on the surface with the multispectral camera is added to the measurement of their depth with optical coherence tomography. Another example allows connecting two different surface states of the upper varnished surface measured by goniophotometry with the identification of these varnish with UV-fluorescence and with their thicknesses measured with optical coherence tomography.     

The palette of the Macchia Italian artist Giovanni Fattori in the second half of the xixth century

Giovanni Fattori (Livorno 1825–Firenze 1908) is the most representative artist of the Macchiaioli's current, an early group of Italian plein-air artists, whose work anticipates, in the xixth century, that of their younger contemporaries, the French Impressionists. The study, performed by a multidisciplinary team made up of scientists and conservators, presents the results of the scientific characterization carried out on a group of 10 paintings made by Fattori between 1854 and 1893 and shows the way he used complex mixtures of a large variety of traditional and synthetic pigments, ranging from lead white, found pure and also extended with calcium carbonate, natural barite and gypsum to zinc white, from red ochre to cinnabar and vermilion, from yellow ochre and Naples yellow to chrome yellow, cadmium yellow and zinc yellow, combined with many other ones reported in details. This paper highlights the evolution of his painting technique during a time of great technological and social innovations and puts forward some hypothesis on his awareness about manufactured pigments, i.e. tube paints recently introduced into the artists’ circles. The wide range of pigments and their different quality among the same synthetic products suggest that the artist used all the available materials, and that picking out the pigments he retained the early xixth century artists techniques, such as the use of mineral earths and Prussian blue, similarly to his contemporary Italian artists Federico Zandomeneghi and Telemaco Signorini, but he also experimented new and peculiar pigment mixtures in the making of “colored darks” and an innovative use of the grounds in the final composition, that are also distinctive features of the French Impressionists. This work is aimed at contributing to overcome the lack of a comprehensive overview on the widespread historical and scientific data collected up to now on the Italian paintings in the xixth century, which has been severely underestimated with respect to previous art movements.     

La Medusa by Caravaggio: characterisation of the painting technique and evaluation of the state of conservation

The oil painting “La Medusa” executed by Caravaggio at the end of the XVI century on a wooden shield, was investigated by integrated physical–chemical and analytical methodologies in order to obtain scientific data capable of elucidating the state of conservation and the painting technique. Optical (OM) and electronic (SEM-EDS) microscopy, micro-FT-IR spectroscopy, gas chromatography–mass spectrometry (GC–MS) and pyrolysis GC–MS were applied on two microfragments and some organic samples obtained by solvent extraction using the swab cleaning technique. The obtained results indicated that Caravaggio probably reused an old shield as a previous gypsum preparation layer has been detected under the original painting layers. He used white lead, natural earths, verdigris and lead–tin yellow type I mixed with drying oils to paint. The considerable amount of amorphous particles of copper chlorides found in the green pigment verdigris suggests that it could have been produced according to the ancient recipe of verde salsum described by Theophilus. Mordant gilding has been identified on the upper part of the shield that can be related to an abandoned experiment to give the painting a mirror-like reflecting effect. Three different varnishes layers have been detected above the painted surface. The original and restoration varnishes have been identified and they contain a mixture of drying oil, mastic and turpentine and some beeswax. Cleaning tests, performed with different organic solvents, suggest the use of isopropyl alcohol as cleaning agent because it is less efficient in comparison to others solvents; thus it ensures a careful and controlled removal of the varnishes.     

Non-destructive methods for chemical, optical, colorimetric and typographic characterisation of a reprint

The quality of production (e.g. paper, typesetting, reproduction of illustrations, printing and bookbinding) of a book (reprint) is very important. The quality of a 1978 reprint of a book from 1921 was studied using standard and non-destructive testing methods such as microscopic and spectroscopic techniques. Chemical, physical and colorimetric properties of the papers, colour differences of the prints and typographic tonal density were analysed. Results showed that the reprint is not an identical copy of the original. Some of the differences in the reprint compared with the original (e.g. typographic tonal density) could easily have been avoided while others (e.g. structural and optical properties of paper, colour prints) are unavoidable, mainly because of the influence of internal and external factors on ageing. Ageing influences the properties of paper and colour print: optical and colour properties deteriorate and colour fades. It is concluded that precise and systematic evaluation of the properties of an old book should be carried out before a reprint is prepared. The results of the research, using non-destructive methods such as microscopy, spectroscopy and image analysis, are useful for characterising the properties of paper and printing ink, typography and reproduction of illustrations.     

文萃

淘气包 梁思成年轻时是学建筑专业的,但他在音乐和绘画方面都有很好的修养。他在美国宾夕法尼亚大学留学时,宾大要求学生自己设计作品,他的第一件作品便是给林徽因做了面仿古铜镜。那是用一个现代的圆玻璃镜面,镶嵌在仿古铜镜里合成的。铜镜正中刻着两个云冈石窟中的飞天浮雕,飞天的外围是一圈卷草花纹,花环与飞天组合成完美的圆形图案,图案中间刻着：徽因自鉴之用,思成自镌并铸喻其晶莹不珏也。     

Use of ZnO nanoparticles for protecting oil paintings on paper support against dirt,fungal attack,and UV aging

Zinc oxide nanoparticles were prepared and used for surface treatment of oil paintings painted on paper supports. The prepared coating mixture containing 2% of ZnO nanoparticles showed excellent transparency. The effect of coating on protecting the paper support and paintings against microbial attack by Trichoderma reesei and Aspergillus niger, dirt accumulation, and UV aging was studied. Coatings containing ZnO nanoparticles enhanced the durability of linseed oil-based paintings toward UV aging regarding the change in color. Coatings containing ZnO nanoparticles improved resistance to microbial attack when subjected to inoculums containing T. reesei or A. niger fungi. In addition, coatings containing ZnO nanoparticles reduced accumulation of dirt on oil paintings when left in open air for 6 months; cleaning of paintings was quite easy compared to the non-coated paintings or those coated with the varnish without ZnO nanoparticles.     

The law of one price,noise and “irrational exuberance”: the auction market for Picasso prints

We use prices realized for Picasso prints at auctions worldwide, as well as the 100 prints that comprise his Vollard Suite, to test the law of one price: the proposition that identical art objects sold contemporaneously should command the same price regardless of the auction house or geographic region where the sale takes place. Picasso is the most prolific printmaker of the twentieth century and, from 1977 to 2004, his prints appreciated in price significantly faster than the prints of modern masters as a whole. We find that Picasso prints sold in the United States command higher prices than in Europe. However, prices realized at Sotheby’s in New York are no longer higher than at Christie’s in New York, nor at Kornfeld than at other auction houses. We find evidence of “irrational exuberance” in the transitory nature of the extraordinary prices realized for the Picasso prints included in the 1997 sale of the collection of Victor and Sally Ganz at Christie’s in New York. More generally, we find substantial noise in auction outcomes, a result well known to savvy auction goers.

一个农民与一条龙

《临安水龙》曾去北京参加广场文化献演,又两次远赴法国表演,赢得一片赞誉。使这条龙活起来、舞起来的是一个名叫程行的人。他原是农民,现在还住在临安青山朱村。     

Islamic glasses from Al-Andalus. Characterisation of materials from a Murcian workshop (12th century AD, Spain)

Rescue archaeological excavations at an urban glass workshop of the 12th century AD in the city of Murcia (Spain) have provided one of the few evidences of glass production in the ancient Islamic territory of Al-Andalus. This paper reports the results derived from a chemical–physical characterisation study carried out on a representative sample set of glass fragments and industrial debris from that workshop. The main objectives of the research were to contribute to the knowledge of the type of glasses produced and provide some insights into the technology developed to obtain different colours in glasses. The resulting data indicated that both high-magnesia plant ash (HMG) soda-lime-silicate and soda-lime lead-silicate glasses were produced. They also indicated a deep knowledge of glass colouring techniques, which suggests that a careful control over the glass melting processes was achieved. Among others, the occurrence of bulk-coloured silver yellow and copper ruby red transparent glasses prove the skills reached by Murcian glassmakers. These results shed new light on the Islamic glass technology of a geographical area in which, up to now, little compositional and technological data from glass workshops were available.     

The Complementarity Between the Collective and the Individual

Besides his activities as a theoretical physicist, the Belgian Léon Rosenfeld cultivated and showed a lively concern for history of science since his student years. This paper is a study of his publications, correspondence and other endeavours in history of science, mainly during the early Cold War period, in order to explore his essentially Marxist views on science and society and how they differed from those of other Marxists scholars, most notably John D. Bernal and Boris Hessen.     

Reading and Writing the Passions in Duchenne de Boulogne's Mécanisme de la physionomie humaine

This paper examines Duchenne de Boulogne's Mécanisme de la physionomie humaine (1862) as a limit case between Foucauldian epistemes of signification. Electrically inducing ‘expression’ in his subject's face, Duchenne, a neuro-physiologist, claimed to have discovered the true ‘orthography’ of the passions. He photographed and published his experiments to offer the art world a positivist corrective to the historically ‘arbitrary’ representation of emotion. The narrative accompanying the photographs provides the basis for this analysis which focuses on how Duchenne used the image/text idea of an ’orthography‘ to shape his technologically mediated expressions with a Renaissance and Classical poetics of resemblance and representation. Making an analogy with linguistic ‘units’, Duchenne located a scene of writing under the facial flesh where action was ‘transfigured’ into passion. The Classical debate on the origin of language and the Renaissance physiognomic tradition inspired his discourse, which failed to grasp the modernity of his technologically mediated passions.     

A new family of high viscosity polymeric dispersions for cleaning easel paintings

The procedures for making and applying a new family of high viscosity aqueous polymeric dispersions based on poly(vinyl alcohol)-borax (PVA-borax) matrices are presented. A specific system of this type has been used to remove an oxidized varnish coating from the surface of “Coronation of the Virgin with Saints”, a 15th century egg tempera painting on wood by Neri di Bicci (Florence, 1418–1492). FTIR spectra showed that the oxidized varnish was constituted of highly aged shellac resin. Good cleaning performance was attained when the liquid portion of the dispersion consisted of a mixture of water and acetone. Rheological investigations indicate that the acetone content does not affect the mechanical properties of the polymeric dispersion. Those mechanical properties permit easy removal of the cleaning agent simply by peeling it from the surface by means of a forceps or spatula once it has carried out its cleaning function. Optical microscopic and FTIR investigations show that the cleaning agent is able to remove the oxidized varnish coating from the surface of the Neri di Bicci painting without leaving detectable residues.     

Non-destructive identification of inorganic pigments used in 16–17th century Albanian icons by total reflection X-ray fluorescence analysis

The application of total reflection X-ray fluorescence (TXRF) to the analysis of inorganic pigments used in five Albanian icons painted by Onufri Qiprioti, in the period from the end of 16th to the beginning of 17th century is presented. After removing the protective varnish with a solvent, a dry cotton-wool bud (Q-tip) was rubbed over the painted surface to collect the micro-samples. Samples, covering the main colors and their hues, were collected of each icon. A part of the small amount of the sample was transferred to a glass carrier and analyzed by TXRF. Main types of inorganic pigments used for different colors could be identified. The results indicate a palette which included white lead, calcium white, gold, orpiment, yellow and red ochre, vermilion, red lead; a cooper based green pigment (malachite or verdigris) and smalt.     

A study of the blue colors used by Telemaco Signorini (1835–1901)

Telemaco Signorini (Florence 1835-1901), one of the most important Italian painters of the 19th century, was particularly famous among his colleagues for his way of depicting dark details and shadows by using primarily blue colors. The restoration of his painting Pascolo a Pietramala (c. 1889, Galleria di arte moderna, Palazzo Pitti, Florence) gave the authors the opportunity to study Signorini's blue palette using non-invasive fiber optics reflectance spectroscopy (FORS) in the ultraviolet (UV), visible (vis), and near infrared (NIR) regions (350-1700 nm). Furthermore, to help in the identification of the pigments used, a suitable spectroscopic database was created for Prussian blue, artificial ultramarine blue, Thénard blue (or cobalt blue), and cerulean blue modern blue pigments, in masstone and in mixtures with lead white as well as zinc white. The main pigments used by the artist in the aforesaid painting were found to be Prussian blue, artificial ultramarine blue, Thénard blue (or cobalt blue).     

HMTY-KM (black copper) and the Egyptian bronzes' collection of the Musée du Louvre

At the instigation of the Musée du Louvre's Department of Egyptian Antiquities, an intensive programme to study black bronze has been carried out at the Centre de Recherche et de Restauration des Musées de France. Systematic research has been undertaken on the museum's collection to identify objects that might have an intentional black patina.The same experimental protocol has been applied to all the objects, alllowing this study to be one of the most important coherent investigation on this type of bronze decoration. It involves the use of non-invasive analytical methods in order to obtain the maximum amount of information possible about the chemical nature and structure of the surface layer. The protocol makes it possible to compare objects and to propose an interpretation of how this decorative technique evolved during the Egyptian period.Based on previous stylistic investigations (by J. Cooney, 1966) and personal observation, sixteen objects dating from the Middle Kingdom to the Late Period were selected. Thanks to elemental analyses, twelve of them were identified as being intentionally patinated. Only ten of these could be described as hmty-km, because the base patinated alloy contains small amounts of gold and/or silver and the black patina is made up mainly of cuprous oxide Cu₂O (cuprite). Among the four other objects, one patina is very close to the black bronze patina, but contains neither gold nor silver. Three other pieces have an unusual patina. A lack of other comparable examples makes it very difficult to determine whether the patinas are of ancient origin.