Studies
- Preface
- Origins of the Digital Catalogue of Eynard’s Photographic Work
- Eynard and the birth of photography
- Eynard the Photographer (1840-1855)
- Chronologie
- The Role of Architecture in Eynard’s Work
- Fashion in the mirror of Eynard’s daguerreotypes
- Conservation and the material history of the daguerreotypes taken by Eynard
- Impressum
Annexes
Conservation and the material history of the daguerreotypes taken by Eynard
What is a daguerreotype?
The daguerreotype is the first photographic process to be entered in the public domain. It is the ancestor of today’s photographs. The daguerreotype produces an image captured by a thin layer of silver on a copper plate. The result of an exposure is therefore unique and non-multipliable, that is, each piece cannot be reproduced in two or more specimens (unlike other processes that were contemporaneously discovered and experimented with, such as the calotype). The quality of the images obtained by daguerreotype photography is exceptional. According to the “chemistry,” as preparing and developing the plate came to be called, and the degree of polish achieved on the plate’s surface beforehand, a result akin to the image in a mirror can be obtained. The particularity of the image captured on a daguerreotype is that it appears either as a negative or a positive. Indeed, according to the orientation of the plate and the angle it is viewed at, the image will appear to change as you handle it.
The daguerreotype was developed thanks to the research carried out by Louis-Jacques-Mandé Daguerre (1787-1851) and Nicéphore Niépce (1765-1833) starting in 1827. It was only after Niépce’s death, however, that Daguerre discovered, in 1835, a way of fixing the image on the plate. Several more years were needed to refine the process, then on 19 August 1839, during a session of the French Académie des sciences, François Arago officially presented the invention. Ever since, that day has been considered the birthdate of photography.
With the passing years and additional improvements to the invention, the time it took to pose was reduced from several minutes to a few seconds. The cost of the process would nevertheless remain high. The apparatus alone for taking daguerreotypes cost around four hundred francs, the equivalent of nearly four months’ pay for the average Parisian laborer at the time. Moreover, the different toxic fumes involved in the process were a serious health hazard. Little by little, daguerreotypy was replaced by simpler processes that also made it possible to realize several proofs from one and the same negative. It is thought that by the 1860s only a few nostalgic lovers of the process practiced it still.
The size of daguerreotypes does not exceed 21 × 16.5 cm. In this format they were called daguerréotypes pleine plaque, and “whole plates” in English. Daguerreotypists could purchase plates in smaller dimensions corresponding to the whole plates (in English the plates in smaller sizes were known as half, quarter, sixth, ninth, and sixteenth plates).[1]
Manufacturing process
Publicly announced in 1839, the daguerreotype represents one of the oldest photographic processes that enabled the user to obtain a unique image without the intermediary of a negative.
The process involves two major phases, i.e., first, capturing the image on a photosensitive support; then stabilizing, or fixing, that image. A series of operations demanding a high level of both precision and cleanliness was required because the least unsteady gesture could compromise the final outcome of the photograph.
First came the silver plating of the copper plate’s surface by lamination (rolling on of the silver) and/or galvanoplasty (that is, galvanizing, or coating, with a thin layer of metal – silver again – by electrochemical means). The plate was cleaned using “a few drops of any oil; then one add[ed], using a little muslin bag containing it, tripoli or violet iron peroxide.”[2] Application was done with a circular motion, then up and down, and left and right. This operation was completed by “drying” the plate using jeweler’s rouge (iron oxide) and acidic spirits of wine, made of ethyl alcohol and silver nitrate dissolved in distilled water or spirit of turpentine.
The plate was now ready for iodizing. With the formation of a thin layer of silver iodide, this operation served to sensitize the support to light. Sensitization resulted in the plate’s turning yellow, the intensity of which depended on the time of the reaction. The plate was then loaded into the camera obscura (literally dark chamber), the camera, the closed box with its one opening, and exposed to the light, and the latent image that formed on the surface would be revealed, that is developed, by exposure to mercury fumes.
The process ended with fixing the image. The plate was plunged into a saturated solution of water and sodium hyposulfite followed by a bath of distilled water alone.
A series of improvements were introduced over time. The use of a prism during the exposure notably made it possible to reverse the image, which was normally a mirror (laterally reversed) image of reality. As for gilding, also called gold toning, this technique allowed the daguerreotypist to heighten contrasts while chemically stabilizing the image. Finally, exposure times were shortened thanks to the use of certain halides and ongoing improvements in optics.
To conclude the process, the image obtained was inserted in a hard case, a protective casing to preserve it from physical and environmental damage. Numerous models were available but the two most widely used were the “European” case and the “Union” case. The former was done using églomisé glass (back painted or back gilded; in the case of daguerreotypes, the center of the glass was untouched and only the outer area around what would be the photographic image was painted) and an ornamental cardboard mat (also called a passe-partout), the whole being sealed with gummed paper. The Union case was similar to the ones already being used to embellish miniature paintings. The plate would be positioned in a brass passe-partout and placed under a protective glass cover. This was then set in a case made of wood, papier-mâché, or a material that was malleable when heated (what would later come to be called a thermoplastic material). With Union cases it was usually a steam-heated mixture of colored sawdust and shellac. This material would be covered with copper and decorated with ornamental motifs.
The state of conservation of the Eynard Collection
The daguerreotype is a composite object then that brings together materials with different characteristics. It is a very fragile object as well, one liable to be irreparably damaged simply by being exposed to air.
The daguerreotypes from the Eynard Collection have been the focus of a restauration campaign that began in 2011 and is ongoing as of this writing (2020-2021). The campaign has been an opportunity to assess and list the damage occasioned over the years by handling and inadequate conditions in conserving these early photographs.
The daguerreotypes showed various states of conservation. The objects were covered in dust and grime. Torn or incomplete sealing strips allowed oxidizing agents in the air to penetrate the housing and come into contact with the plate, causing oxidation and sulfurization of the layer of silver that constitutes the image, and forming series of cloudy tarnished areas. The colors, darkening over the years and ranging from yellow to reddish violet, even bluish black, indicate both how thick the layer of corrosion is and how far the deterioration has advanced. Significant deterioration can therefore render the image totally illegible.
These areas of fogging due to oxidation are generally concentrated near the edges of the piece or correspond to possible fissures in the protective glass, where the air can penetrate the protective casing.
The manufacturing process can also cause other visible alterations to the image. For example, certain stains can be attributed to a poorly rinsed plate or to the presence of deposits occasioned by the deterioration of the glass; green dots correspond to oxidation of the copper in areas where the layer of silver is wanting. Flaking of the silvered plate can also be ascribed to imperfections in one or more of the steps in the production process.
On most of the plates, damage of a physical, rather than chemical, nature is also visible. It is well known that the least touch, the barest hint of a fingerprint, or simple rubbing can cause irreparable damage to the image; scratches and abrasions can also appear in this way.
Furthermore, the presence of mold was observed in a significant part of the collection. The spores, borne by air and dust entering through gaps in the seals, were deposited on the plate, where they subsequently grew and spread.
Finally, the protective glass plates sometimes display an ongoing process of deterioration called crizzling (known by several names, including sick glass and weeping glass). In the case of the daguerreotype cases, this is seen in networks of cracks on the paint of églomisé glass coverings and results in a compromised protective glass covering and contact with the air. Broken and cracked glass coverings were also found and listed. In the majority of the cases, the plate showed an oxidation of the layer of silver oxide mirroring the damaged area of the glass.
The conservation-restoration project
Numerous treatments have been tested and studied over the years. The earliest efforts basically strove for a better aesthetic restoration of the object, leading to the removal of original elements and the use of materials for which precious little documentation existed showing how they would interact with the support.
Today we have a better understanding of the mechanisms of physical and chemical change; together with the mission to transmit this heritage to future generations, this knowledge guides a prudent minimalist approach to the conservation-restoration treatments that can be employed. An intervention aims first to stabilize the piece and only act when the damage is progressive as in the case, for example, of damaged housings that allow air, dust, and/or humidity to reach the photographic plate.
Eight daguerreotypes from the collection were already restored between 1995 and 1998. Unfortunately, the treatment wasn’t documented and – apart from what could be established visually and during succeeding interventions to restore the object – very little information was transmitted to us orally. During this earlier operation, the original mats were partly removed and replaced by facsimiles. The original borders were also removed and replaced by new sealing strips. Some of these elements, notably the passe-partouts, have come down to us and we were able to reinstall them during a more recent preservation operation. The plates would be placed in a snug cardboard holder, preventing any movement, while the original elements were cleaned of all dust and put back in place. The back mat boards was also replaced by conservation-quality ones.
With the aim of long-term conservation, a new restoration campaign for the 148 daguerreotypes was launched in 2011. Each piece was given a detailed examination in terms of restoration priorities and the types of treatment being considered. Nowadays the predominant view favors conserving the plate inside an airtight structure in which the original elements are inserted between new elements while the aesthetic aspect of the object is retained. This structure allows us to isolate the plate from the air and keep it in a stable climate-controlled micro-environment.
Nevertheless, disassembling objects remains a very delicate operation that is to be applied only when conservation of the plate is threatened.
Because their sealing strips show occasional gaps, fifty-nine of the daguerreotypes have been consolidated and disassembly was not considered. Constant monitoring of these objects allows us to verify that the deterioration is stable and not progressing.
The rest of the collection has been given a more advanced treatment. These are the steps involved:
- Case history and condition report of the object: this is a moment of fundamental importance because it allows one to study the materials in their original place, identify the technology employed in producing the object (hallmarks, marks, annotations, labels, etc.), and analyze its material history by carefully examining any visible damage. This information enables us to grasp the causes of the damage that can be seen, plan an intervention, and implement the most appropriate environmental parameters for storing, handling, and displaying the item. Visual documentation of the object starts with this phase: photographs before the intervention enable one to document the state of the piece. This documentation then incorporates additional photos shot during and after the intervention, and serves, along with the restoration report, as a basis for future monitoring of the objects.
- Disassembly of the casing: the “dry” method is preferable, although at times it is impossible to apply. In certain cases, slowly and gradually humidifying the elements in question is called for. This is carried out with the use of gel and special membranes.
- Once the piece has been disassembled, all the elements are separated and cleaned. This entails removing dust and any other extraneous deposits found on the surface of the materials. “Dry” cleaning of elements made of paper or card is preferred because it avoids dissolving surface particles and their subsequent penetration of the support. On the other hand, “wet” cleaning was recommended for the areas of the protective glass originally untouched by paint. No cleaning treatment was performed other than puffs of air from a blower bulb that never touched the plate.
- Weakened and compromised elements have been consolidated. The choice of consolidant was based on its compatibility with a range of supports and the deterioration to be treated.
- Remounting made it possible to isolate the plate from the other material parts and custom-make, if need be, new elements to be integrated with the original mounting. This also allowed us to incorporate original elements that had been replaced during the first restoration. Physically and chemically, the materials integrated in the casing are free of acids and peroxides, and boast a heightened chemical stability. These features are described in ISO 18902:2013 (Imaging materials — Processed imaging materials — Albums, framing and storage materials). Although this International Standard refers to modern phototypes, the field of application can be extended to historical phototypes. This doesn’t only concern the basic materials like the paper and plastic materials (“plastic” in the pre-organic polymer sense of course) used in the casings, but also products that might have been added during reassembly, like glues, pigments used in restoring, even adhesive tapes.
- Finally, each phototype is now stored in an archival box custom designed for the piece in question to ensure the long-term preservation of the item.
All of these efforts, however, would be for naught without the series of preservation measures that were put in place to maintain controlled climate conditions in the storage environment (18°C, 40% relative humidity, and the absence of atmospheric pollutants), and appropriate handling during (limited) consultation or when any of the objects is put on display. Finally, these preventive measures will be capped, once the conservation initiative is completed, by a program for monitoring the current state of conservation and any changes that might occur, to ensure that these pieces will resist the ravages of time long into the future.
[1] Introduction written by the Centre d'iconographie of the Bibliothèque de Genève. For the English vocabulary of daguerreotype sizes here, see, for example, the helpful page on the American Antiquarian Society’s website (https://www.americanantiquarian.org/daguerreotypes-0).
[2] M.A. Gaudin, Traité pratique de photographie, exposé complet des procédés relatifs au daguerréotype, Paris, J.-J. Dubochet et Ce, 1844.