Gustave Le Gray’s salted paper prints
Lisa Barro
Assistant Conservator of Photographs
The Metropolitan Museum of Art
1000 Fifth Avenue
New York
NY 10028, USA
E-mail:
Nora W Kennedy
Sherman Fairchild Conservator of Photographs
The Metropolitan Museum of Art
1000 Fifth Avenue
New York
NY 10028, USA
E-mail:
Abstract
A project to research image tonality in Gustave Le Gray’s salted paper prints was supported by the Getty Conservation Institute and undertaken at The Metropolitan Museum of Art. The project included comparison of techniques described in publications by Le Gray and his contemporaries within and outside France, creation and accelerated ageing of experimental samples based on his methods, X-ray fluorescence (XRF) spectrometry elemental analysis and spectrophotometric image colour characterization of Le Gray’s prints. This paper focuses on the study of Le Gray’s techniques through the historical literature and the characterization of the original prints, with some references to other aspects of the project.
Keywords
Gustave Le Gray, salted paper prints, image tonality, XRF, old hypo, gold toning
Introduction
The nineteenth century French photographer Gustave Le Gray produced salted paper prints in the early 1850s with a variety of image tonalities by using innovative processing methods. Le Gray made a large impact on and shared his techniques with numerous photographers during this period through his widely read practical treatises, first published in 1850, and through personal instruction in his studio where he taught many of the prominent photographers of his time. Given Le Gray’s emphasis on the importance of image tonality, the question arises whether his works remain as he intended or have changed over time. This study was designed with several components. First, the primary source material – the four versions of Le Gray’s practical treatise – were studied and compared with each other and to other treatises from the period. Second, Le Gray’s salted paper prints from three collections were documented with spectrophotometry and chemically characterized with non-destructive elemental analysis using X-ray fluorescence (XRF) spectrometry. Based on the treatises, three separate process re-creation experiments were undertaken. Finally, the experimental samples were submitted to cycles of accelerated ageing, using colour measurements to quantify change. This paper’s primary focus is the study of Le Gray’s salted paper print techniques through his treatises, and the analytical characterization of Le Gray’s prints through XRF spectrometry and through spectrophotometry.
Gustave Le Gray
Gustave Le Gray began his career in the arts as a painter and was a student of Paul Delaroche in Paris in 1842. By 1847, he began experimenting with photography, making daguerreotypes and later salted paper prints. He is included among the innovators in the history of photography for his dry waxed paper and collodion on glass negative techniques. By 1849, he had established a photographic studio (Aubenas 2002). In 1850, Le Gray published the first edition of his influential treatise or manual, which was quickly translated into English and widely read inside and outside of France. He had many students including Maxime Du Camp, Henri Le Secq, Charles Negre, Auguste Mestral, and J B Greene, all of whom became prominent photographers in their own right. In 1851 he was hired to participate in the Mission Héliographique, a project organized by the French Government to document historic monuments. Le Gray’s salted paper images from this period as well as his works made in the Forest of Fontainebleau exhibit a wide range of tonalities: from yellow, to greenish, to more neutral black, to purple-brown. By the mid-1850s Le Gray favoured the albumen process over salted paper printing. His albumen images exhibit a much less varied palette of final image colours.
Le Gray’s Treatises
In 1850, Le Gray published the first version of his Traité Pratique de Photographie sur Papier et Verre (‘Practical Treatise of Photography on Paper and Glass’). Le Gray gradually altered and expanded the treatise, publishing three subsequent editions in 1851, 1852, and 1854. The manual grew from its original 42 pages to an extensive 387 pages in the final version. These texts include recipes for image making, with an emphasis on printing and processing methods for subtly adjusting the palette of final image colours. This reveals Le Gray’s roots as a painter, choosing colours appropriate to subject and sensibility. In the later editions, Le Gray added a second part to the treatise on chemistry and theory. These include an appendix on chemical materials, a treasure trove for anyone struggling to re-create techniques from the period. Unlike a chemically based manual, Le Gray describes adjustments made to materials and their relative quantities in subjective terms, making his precise methodology for any one image impossible to pin down. Through his instructions and the many variations described, however, one gets a very clear sense of how he carefully selected his image colours from the resulting broad gamut of possibilities. Le Gray stands out among his contemporaries, Louis Desiré Blanquart-Évrard and Édouard Baldus among others, as the only one to use gold chloride to adjust image tonalities. His recommendations for extended printing-out times and lengthy hypo or fixation baths are also unusual for the period. Both Le Gray and Blanquart-Évrard show a strong interest in the fine-tuning of colour through the control of hypo bath times. All three French photographers suggest the use of an old hypo bath – a sodium thiosulfate bath that already contains silver salts – to produce finer tones. The method through which they each arrive at this result varies, however. Le Gray achieved the final image colour through careful manipulation of certain steps during print processing. When asked by Marc-Antoine Gaudin during a visit to his studio about how he achieved his ‘exceptional tones’, Le Gray emphasized the lengthy exposure times and prolonged use of hypo with added silver salts. The time-consuming nature of these methods appeared not to
have disturbed Le Gray, whose primary goal was always the creation of a magnificent print.
Exposure
Le Gray significantly overexposed his prints, sometimes leaving the negative and sensitized paper out in the light for one or more days in winter (Gaudin 1853). In his treatise, he described the series of print-out colours produced using these colours to gauge the proper exposure time: ‘Gris-bleu—teinte neutre—violet-bleu— noir bleu—noir—noir bistré—bistre—sépia colorée—sépia jaunâtre—jaune feuillemorte— gris-verdâtre’ (Le Gray 1851). When thoroughly overexposed, high-density regions begin to revert, taking on a lighter look with a metallic bronzy sheen. It was standard practice to expose beyond the final density desired, due to the loss of density caused during fixation. This is described by Baldus as exposing until the whites began to cloud over. However, Le Gray greatly exceeded thesestandard exposure times, describing the bronzing stage as a desirable goal. Blanquart-Évrard warned never to expose the print to the point of bronzing. In contrast, Le Gray exposed the print until the colour was ‘two steps’ beyond the desired tonality for the high and low-density areas. For example, to obtain black tones in the final print, the printed-out colour during exposure for the maximum densities would be sepia and for the highlights, greyish blue.
The old hypo method
Le Gray intentionally used an ‘artificially aged’ sodium thiosulfate bath to fix his prints.1 Using only this bath, Le Gray argued that all gradations of tones were possible, ‘the abundance of which is inexhaustible in the hands of a skillfulpractitioner’. Exposed silver chloride was added to the hypo to imitate a used bath containing silver salts from the processing of many prints. Le Gray was not alone in this practice, though only he specifies use of the exposed chloride salt. Both Blanquart-Évrard and Baldus suggest the use of ‘aged hypo’ and British photographers commonly referred to this type of bath as an ‘old hypo bath’. In essence, it combined fixing with a toning action. According to Le Gray, one could obtain almost all image tonalities, from ‘red to black to light yellow’ by using bath times from less than one hour up to four days, the latter producing the sepia or yellow tones (Le Gray 1851). The older the bath, the better it was, according to Le Gray. However, it was important to add fresh hypo to it when it became ‘cloudy’ so a concern for proper fixation as well as toning is apparent (Le Gray 1851). In a typical fresh hypo bath with an excess of thiosulfate ion, the thiosulfate reacts with unexposed silver chloride to produce soluble silver thiosulfate complexes. If, on the other hand, the equilibrium shifts and there is more silver in the bath, as in an old hypo bath, the thiosulfate reacts with the silver chloride to create an insoluble silver thiosulfate complex that may decompose to form silver sulfide over time (Haist 1979, Ware 1994). If the hypo bath was aged by adding acid, a method that Le Gray recommended against (Le Gray 1852) but was used by Blanquart-Évrard, the acid would decompose the thiosulfate complexes in the bath to liberate sulfur which would react directly with the metallic silver in an image (Haist 1979). In Le Gray’s successful prints, the aged
hypo bath presumably still contained sufficient thiosulfate to clear unexposed silver chloride salts, the extended bath times perhaps compensating for the unfavourable chemical equilibrium. Experimental samples fixed either in the aged or the fresh hypo solutions showed equal resistance to further printing-out when exposed to light. In his 1852 treatise, Le Gray responded to photographers concerned about stability problems with prints made using old hypo baths. Practitioners reported that prints ‘gradually fade and sometimes completely annihilate themselves … particularly in the prints with black-sepia and yellow tones’ (Le Gray 1852). According to Le Gray, the cause for this deterioration was either insufficient time in the hypo bath or a thiosulfate solution with too great a proportion of exposed silver salts. Le Gray responded to these concerns by adding a new section, ‘Procedés Nouveau’ to the treatise in 1852. Here he also adds an acidified gold toning bath prior to the aged hypo. In the previous edition of the treatise the gold bath had been an option post-fixation. He also suggests that if the old hypo bath was to be used, it was ‘absolutely necessary to put the print for an instant in a fresh hypo bath’ as a final step, thus rendering soluble any residual silver chloride or insoluble silver thiosulfate complexes (Le Gray 1852).
Gold toning
Le Gray was among the earliest photographers to gold-tone salted paper prints. Neither Baldus nor Blanquart-Évrard mentions the use of gold in their photographic treatises. Le Gray’s methods for gold-toning changed in each of his treatises. In 1850, as one of a few methods suggested for adjusting image colour, Le Gray recommends a post-fixation sel d’or bath to obtain ‘beautiful velvety tones’ (Le Gray 1850). Sel d’or was a combined gold thiosulfate salt that was first used by photographers to make daguerreotypes more stable.2 The term can also refer to a fixing-toning bath in which a gold chloride solution has been combined with a hypo fixing bath. In 1851, Le Gray changed his directions for achieving the same ‘beautiful velvety tones’ with the post-fixation gold toning bath by adding 5 g of nitrohydrochloric acid or aqua regia to the sel d’or with a reference to ‘Chlorured’Or Acide’ or ‘Acidic Gold Chloride’ listed within the appendices (Le Gray 1851). The recommended proportions, listed in the appendix, are the same except for the use of the term chlorure d’or instead of sel d’or. Therefore, the directions in the appendix contradict those in the body of the text, making it uncertain whether he used sel d’or or chlorure d’or. That said, Le Gray’s descriptions of the gold in the first and second treatise are unclear, particularly as he did not add the acid in 1850. In 1852 in his ‘New Processes’ section, Le Gray switches the toning bath order VOL II Photographic records 535 and recommends toning with acidified gold chloride pre-fixation, expanding the range of possible final image tonalities (Le Gray 1852, 1854). The new process also involves the use of both old and fresh hypo described above. He continues to use one litre of distilled water with one gram of ‘chlorure d’or’, but this time with 25 g of hydrochloric acid. In 1854, Le Gray made one final change to the ‘New Processes’ section. In addition to the separate gold-toning bath, he listed gold chloride as an additive to the old hypo bath. This is essentially a type of sel d’or bath although Le Gray does not describe it as such. The bath still contains the exposed silver chloride salts as in previous editions.
Le Gray’s contemporaries
The techniques and quantities used by Le Gray were compared with those of his French contemporaries and to Talbot, as the first practitioner to publish his methods (Table I). One of the English translations of Le Gray’s 1854 treatise is included to demonstrate the occasional variation in quantity from original to translation. In some cases photographers may have modified bath times to accommodate differences in solution concentration. Le Gray himself significantly increased the quantity of exposed silver chloride added to the hypo bath in 1852 and at the same time recommended a dip in the fresh hypo bath to insure full clearing. Other than his 1850 treatise, the concentration of Le Gray’s hypo bath was higher than that of his contemporaries.