IPERION CHIntegrated Platform for the European Research Infrastructure ON Cultural Heritage

Analysis and Research Methods In Management of Photographic Materials: Gelatin Glass Plate Collections

Users:  Alba Guerrero García, José Fernando Vázquez Casillas
Venue: IPCE, Spain


Analysis and Research Methods In Management of Photographic Materials: Gelatin Glass Plate Collections was created with the intention to give support to an ongoing research, as a part of a case study included in a Ph.D. Initially, we thought about the importance of exchanging knowledge and experiences and try to look for a support to research and collaborate with important institutions, such as in this case the FCG and the IPCE. It could be enriching for the investigation and finally, the project was definitely sent, after permission and consensus with the Calouste Gulbenkian Foundation and IPCE. Spain and Portugal, are two countries of the Iberian Peninsula through which, practically, the whole of this research is being carried out and are being taken as case studies in the field of photograph conservation.
Although in previous Ph.D. research we include in greater depth conservation criteria, management, values and the importance of research with photographic materials and analog archives, we decided to limit this ARCHLAB project only in a photographic typology by the limitations in time. Accordingly, with previous project needs, we decided together with IPCE members to focus our attention in an ARCHLAB proposal on these types of collections. This contribution to previous research aimed to focus on gelatin glass plate negatives processes and the study of deterioration and treatments. IPCE Photographic Archives have a big and important photographic collection about this type of materials and they have a lot of experience in preservation. Part of this research was intended to be nourished through an exchange of knowledge with institution´s staff, which have dedicated decades to these tasks and in order to complete the main project objectives: access and consultation of documentation, reports, data bases, photographic objects and issues related to the conservation treatments carried out by the ARCHLAB provider institution. During the access period, conservators in charge of preservation, research, and display, kindly aided to the investigation development showing the facilities, reports, and documentation related to the photographic objects of interest. In collaboration with them, analytical and critical views were developed on some conservation treatments that had been performed, especially on glass plates photographic objects. During the stay, other IPCE departments were also visited to discuss some specific related issues such as digitization, preventive conservation, graphic documents, and biodeterioration.
Thanks to GGPN ARCHLAB project in IPCE, it has been possible to develop part of this research and to know more about glass plate negatives collections management. It will contribute a lot of positive aspects to the future development and help to finish a complete glossary deterioration in gelatin glass plate negatives which we would like to include in a Ph.D. research at the University of Murcia. Results of this access are now an important part of previous research in this topic and case study.
ARCHLAB Access in IPCE and previous research provided several questions about preservation and deterioration of glass plates negatives which led to multiple discussions and arguments:

  • Why is important to know how to identify glass plate negatives? Why conservators or people in charge of collections must be capable to properly identify photographic processes and his deterioration?
  • What is the influence and how it affects storage systems and environmental conditions in glass plates collections?- Can we recognize, exactly, what are deteriorations in glass plate process in both parts, emulsion, and support?
  • If glass support deteriorates, how other components affect, coats and emulsions binders? What are the main deteriorations that affect glass? How does biodeterioration affect glass?
  • To what extent is important to take into account the photographic process, albumen (most rarely in glass plate), collodion or gelatin, when making decisions about the type of treatment? What are the main arguments we have to take into account when we are going to do a conservation treatment in a deteriorated glass plate?
  • What is the “best option” or conservation treatment for a broken and severely damaged glass plate? Which things will be needed to take into account to establish the criteria for our decision?
  • In the case of broken and emulsion cracks plates, housing or sandwich mount? Cardboard or Glass? What are the problems that each one presents? Can we use other types of materials in sandwich mounts? What could be the most suitable?
  • What do we have to take into account when making a sandwich? Is a full seal recommended?
  • What is the “ideal” climate and environment for photographic objects of this type? Is the historical climate of objects taken into account in the preventive conservation of photographic materials an important thing to make a choice? How would an abrupt, even controlled, change of “ideal” environment affect glass plates?

One of the important objectives of this proposal was to contribute, promote and disseminate photograph conservation research in Spain because in this field there are still many limitations (educational, professional and working opportunities) when compared to other countries. This research aims to provide a better knowledge about the photographic process through the exchange of experiences between institutions as well as reviews of previous research carried out in this field. Also, as previously mentioned, it is intended to carry out a deteriorations study that affects all parts that compose photographic objects, support, and emulsion, that leads us to a better understanding of the artifacts. By knowing these aspects, we can make better decisions regarding conservation treatments. Another topic of this research was to perform a review of types of storage made in glass plate negatives, as well as the behavior of glass (as a photographic support and a mounting material) before environmental conditions, good and adverse, even conducive to biodeterioration and how this factor could affect to the material. A previous glass deterioration also affects emulsion in multiples factors. Another fundamental aspect is to shed more light about the choice of materials used for mounting deteriorated plates, besides the importance of being able to distinguish the type of photographic process before making a decision on how to carry out an assembly. In short, to study the behavior of all materials that make up glass plates, focus in this case gelatin glass plate, and to contribute to investigations in conservation treatments as well as to determine the importance of the environmental factors and climate in the life of the object to take them into account before any choice.
Different processes were analyzed and compared their characteristics, collodion and gelatin glass plate negatives, establishing different considerations and guidelines in the treatment for each one. The main treatments developed in IPCE in these materials were related to general conditioning: cataloging, cleaning, and storage. We took into account especially objects with greater deterioration such as broken plates, some of them provided with different housings like differently customized sinks matts, sandwiches between glasses, etc.
Special attention was also given to glass deterioration, both, as a photographic medium and as a conservation material used in mountings (sandwich between new glasses), which was studied and observed its behavior in adverse environmental conditions such as high relative humidity and inadequate storage. This, logically, results in deteriorations in the material that affected its physical-chemical stability and aesthetic characteristics. The proliferation of microorganisms and mold, whose releasing acids that attack the surface, deteriorate the glass by modifying its texture, weakening and losing its transparency. Crizzling is another chemical deterioration that occurs, above all, in high RH conditions, in which glass progressively acquires a milky color, becoming translucent and fragile. Unprotected storage that leaves the glass in contact with others glasses, is also one reason for deterioration, giving rise to the annoying Newton rings, creating iridescence on the glass surface and altering aesthetics values of the object.
Also, when we talk about sandwich mountings we need to understand that the behavior between two glasses, one new and the original old, is different, and both keep in contact could cause reactions because objects movement are not the same. For all these reasons, is very important the fact that two glasses do not touch each other in a mounting, as well as to leave a small air space between both. This will help to avoid stains or mold growth and the transfer of emulsion too. To know these particularities and how to detect these behaviors about glass as a support and as a material of assembly is very important for photographic glass plates collections preservation because any irregularity detected in materials will be a warning sign that something is not going well. In the case of glass as a photographic medium, if it deteriorates, it will directly affect the emulsion and advance of this deterioration will weaken it, even going to expel photographic coat from the glass support.
In analysis and evaluation of conservation treatments, we discuss advantages and disadvantages in the use of glass as a mounting material (sandwich) for deteriorated plates, like another kind of housing. It is very important to take into account the type of glass that we are going to use (most stable in chemical terms), photographic emulsion on which we are going to make the plate sandwich (due to different chemistry and behaviors between photographic objects), type and level of deterioration and the importance of placement separators between glasses so that the aforementioned deteriorations do not occur. Likewise, a permanent total sealed of the assembly is not recommended and is very discussed between conservators, because a change of environmental conditions together with other factors inherent in photographic processes (for example, vapors that can release some photographic processes like collodion emulsions) could create a microclimate and condensation inside, being hazardous for the object. The inside of the glass may experience condensation of the moisture, which can be transferred to the photographic object. Therefore, some conservators recommend and it is desirable, to leave a little window on each edge (parallel) in order to create a small air circulation in the sandwich between new glasses and the negative. In IPCE glass plate negatives, different mountings are employed. This conservation mounting system is one of them in some cases.
The use of consolidation adhesives in broken plates mounting is also very discussed and is not really clear about his convenience. Several kinds of research have obtained different results. An important thing when we sealed a glass plate, instead of this, is the use of cardboard spacer or separator to leave a small air flow between both glasses. In addition, cardboards spacers allow the movement of gelatin and glass, dampening the variations of temperature and moisture both external and internal. Also, accompanies the irregularities of the emulsion without the folds being pressed or the tears increasing with the thickness difference of the spacer. These conservation mountings provide above all stability to the glass plate, allow a more safety handling and it is even possible the digitization of the most deteriorated plates in safer conditions. In the case of sink mats and housing, the paper is a very stable and inert material when has a good quality, does not usually cause problems or reactions in photographic materials. It is safe but its physical stability and handling can be more complicated because, in the case of broken plates, the fragments are loose. However, sometimes, opting for these types of storage systems is safer and is the best option if we are not aware of how the other materials will react. In the case of use, other types of materials like glass substitutes such as acrylics plastics, methacrylates (Plexiglas, Acrylite etc. used also in mountings, displays in object conservation), in plate sandwiches are not a safe option. Plastics also present problems such as electrostatic charge (which, in the case of raised emulsions this can be attracted as well as other particles) the great adhesion of dust, the tendency to abrasions etc., in spite of the advantage of less cost and less weight than glass and UV filters that containing some of them. This variety of more new materials still needs more research. Borosilicate glasses such as Pyrex are the most suitable for sandwiches between glasses due to its great chemical stability and good resistance to temperatures and environment. Similarly, as we have pointed out several times, insist that further research on this subject is needed.
Although glass plate negatives are obsolete objects, it is important to preserve them since they are photographic originals and both, positive and negative, are very important for research because they contain valuable information that can not be appreciated simply in a copy image or digital archive.
In summary, it is still necessary to continue the research on these issues in order to improve storages, mounting systems and conservation treatments of some photographic objects. We need to collaborate not only with other conservators but with experts in other disciplines that give us differents points of view and to enrich our conservation work. Similarly, the most important of all, in addition to conservation treatments, will always be the environmental conditions where our collections are preserved. This environment and the objects inside must be periodically controlled, avoiding HR and temperature fluctuations, and establishing a balance that respect the parameters suitable for each photographic process as well as the historical climate in the life of the artifacts where they have been previously (if known), because one of the most potentially hazardous in stability of photographic materials are in environmental abrupt changes.

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