Data & Analytics

22 views

International research on the conservation and restoration of face-mounted photographs

International research on the conservation and restoration of face-mounted photographs
of 7

Please download to get full document.

View again

All materials on our website are shared by users. If you have any questions about copyright issues, please report us to resolve them. We are always happy to assist you.
Share
Tags
Transcript
  V  OL IIPhotographic materials 665 International research on the conservation andrestoration of face-mounted photographs  W Wei Netherlands Institute for Cultural Heritage (ICN)PO Box 76709NL-1070 KA Amsterdam The Netherlands Keywords  face-mounting, Diasec®, photograph conservation, aging, cleaning, acetic acid Introduction Beginning with the patented Diasec® method, face-mounting of photographshas become popular among artists for displaying their works. Increasing numbers of such works are finding their way into important collectionsaround the world. Face-mounting provides depth and colour saturation tophotographs, similar to varnish on a painting. It supposedly also providesprotection against ultraviolet (UV ) light degradation, and lends mechanicalsupport for the often large photographs (well over 2 × 2 m), e.g. some of the srcinal works by Demand, Gursky, Ruff, and Struth. The face-mounting process has been described in detail elsewhere (Jürgens2001, Pénichon and Jürgens 2001, Pénichon, Jürgens and Murray 2002,Pénichon and Jürgens 2005). A face-mounted photograph consists of a poly (methyl methacrylate)-PMMA sheet adhered directly to the emulsion (face) of the photograph, often a chromogenic print, see Figure 1. The composition of the adhesive is proprietary, but is a type of silicone sealant. Prints can besupported with a backing plate, sometimes aluminium or Dibond® which isa composite panel comprising an aluminium face and backed with athermoplastic core. Some systems use double-sided adhesive sheets instead of a sealant.  Abstract   The face-mounting of photographs with PMMA, poly (methylmethacrylate), sheets has becomepopular among contemporary photographers for mounting their work. Face-mounting provides asaturation of colour and a sensation of depth, similar to varnish on a painting. Although some have claimed that face-mounting is a protective measure,recent observations indicate thatdamage and ageing  will be futureproblems. Furthermore, because thePMMA is part of the object, and not asheet placed in front of thephotograph, cleaning is also a majorissue. An international network iscarrying out research to developguidelines for the conservation andrestoration of face-mountedphotographs. The initial results of thisproject are discussed in thiscommunication. Résumé  Le collage de face des photographiessur des feuilles de PMMA (méthacrylatede polyméthyle), est devenu populaireparmi les photographes contemporainspour encadrer leurs travaux. Le collagede face fournit une saturation descouleurs et une sensation deprofondeur, semblable au vernis surune peinture. Même si certains ontrevendiqué que le collage de face est unemesure de protection, des observationsrécentes indiquent que les dégâts et le vieillissement seront les problèmesfuturs. De plus, étant donné que lePMMA est partie de l’objet et non unefeuille posée devant la photographie, lenettoyage est aussi un problèmemajeur. Un réseau internationalaccomplit des recherches pourdévelopper des lignes de conduite en cequi concerne la conservation et larestauration des photographies colléesde face. Les premiers résultats de cetterecherche sont débattus dans cecommuniqué. Synopsis  El trabajo de montaje de fotografíascon láminas de PMMA, poli(metilmetacrilato), se ha popularizado entrelos fotógrafos contemporáneos paramontar su trabajo. El trabajo demontaje ofrece una saturación de colory una sensación de profundidad,similar al barniz en una pintura. Aunque algunos han afirmado que eltrabajo de montaje es una medida Figure 1. Schematic cross-section of a face-mounted photograph   As with other contemporary works of art containing new materials andtechniques, questions are being raised about the conservation of face-mountedphotographs. Two issues in particular appear to be troubling. The first is thatthe sealant used in the Diasec® process releases acetic acid during curing whichis trapped between the PMMA sheet and the photograph, possibly accelerating damage to the one or the other. The acid also escapes by diffusion throughthe edges of the object, or through the PMMA or photograph if there is nobacking board, creating storage problems with nearby objects sensitive toacetic acid, or with the photographs themselves if kept in closed containers. The second issue facing photograph conservators is surface treatment.PMMA is known to attract dust, and is extremely sensitive to scratching andchemical attack. The PMMA sheet is irreversibly mounted to the photo-graph and is thus part of the object. It is subject to the same ethical criteriafor making treatment decisions as for other art objects. Face-mountedphotographs can therefore not be treated in the same way as sheets of   protective PMMA or glass used as glazing in front of paintings or photographs.Unfortunately, many museums are not aware of these issues, and there aremany examples of face-mounted photographs which show patterns of finebut large (circular) scratches characteristic of personnel wiping the photographas if it were a window.In order to address these and other important issues related to theconservation of these objects, an international network was set up in 2004 toassess and conduct research into this area. The member institutions and many of the current participants of this “Global Face-Mounting Initiative”, can befound in the preface to this paper. The ultimate goal of the research is to augmentand further develop sound guidelines for the preservation and conservationof face-mounted photographs. The network is looking at the following areas:1. Survey of known problems:   Development of a damage atlas for face-mountedphotographs2.Cleaning and restoration/repair of surface damage•Practical tests to determine the effect of cleaning methods on thecondition of face-mounted photographs•Find methods for “invisibly” filling and/or polishing out surface scratches3.Aging and storage•Artificial/natural ageing, and diffusion experiments to determineproper display and storage conditions. The main results and preliminary conclusions of all of the network efforts todate are briefly reviewed here. Damage atlas  The technique of face-mounting photographs has only existed for around 30years (Jürgens 2001, Pénichon and Jürgens 2001, Pénichon, Jürgens andMurray 2002, Pénichon and Jürgens 2005). The conservation issues are thusbeing studied in order to anticipate and avoid possible future problems. Inorder to guide this research, a survey is being taken of the kinds of “damage”and long-term ageing which can already be found on face-mountedphotographs. Formal inventories have been conducted in Belgium (Grieten2005), the Netherlands (von Waldthausen and Wei 2007) and Switzerland(Zorn 2004) and the United States (Murphy 2002), using specially designedquestionnaires. Furthermore, observations have been made during other ad hoc   visits to other museums and galleries around the world. Thus far, “damage” which has been observed can be roughly divided intothe following four groups:• Surface contamination:   Some form of surface contamination was found onall objects, including dust, grime, smudges, droplets, oil films, traces of  wrapping materials (see Figure 2a), fingerprints, and other markings. Theprotective film used on PMMA when it is first delivered also seems toleave invisible traces, which appear later (von Waldthausen and Wei 2007).• Surface damage: Many face-mounted photographs show scratches orabrasion. These range from the occasional nick, see Figure 2b, to broaderpatterns of shallow scratches due to cleaning, as mentioned previously.• Transport damage: Many forms of surface contamination and scratches are aresult of poor handling in transport. In addition, corner damage has alsobeen observed where a heavy face-mounted photograph was dropped. Works have been pierced by forklifts, causing irrevocable damage.• Colour changes and aging: Only a few cases of long-term ageing (yellowing)of face-mounted colour photographs have been found. This may be dueto the fact that the oldest face-mounted photograph examined to date,dates from 1989. (For this discussion, “long-term” ageing refers here togeneral discolouration or fading associated with the natural ageing of unmounted photographs.) protectora, observaciones recientesindican que el daño y el envejecimientoserán futuros problemas. Además,como el PMMA es parte del objeto, y no una lámina situada delante de lafotografía, la limpieza también resultauna cuestión importante. Una redinternacional está realizandoinvestigaciones para desarrollardirectrices de conservación y restauración de fotografías de trabajomontado. Los resultados iniciales deeste proyecto se debaten en estacomunicación. 666 ICOM C OMMITTEE   FOR   C ONSERVATION , 2008V  OL II  V  OL IIPhotographic materials 667Occasionally, “spots” of discolouration are observed, see Figure 2c. Whether or not this should be called “long-term” ageing is open todiscussion. However, the cause is most likely an imperfection occurring during the developing or mounting processes. A further form of ageing isdelamination of the photograph from the PMMA sheet along the edge, seeFigure 2d. This may be caused by ageing of the sealant or double-sidedadhesive, or thermal expansion/contraction. It has been suggested that storing heavy photographs on edge may cause or accelerate delamination. Cleaning and conservation of face-mounted photographs Practical cleaning tests are being conducted by a number of partners. Over60 combinations of materials and methods are being considered to handle the various types of surface contamination found thus far. A summary list of materials is shown in Table 1, divided into dry and wet techniques, including those already in use in conservation practice, and commercial products. Ingeneral, the techniques are first applied to samples one time to determine how effective they are. They are then applied a number of times to simulaterepeated cleaning over many years. Table 1. Materials being considered for cleaning PMMA face-mounting materials  DryWet Antistatic clothsCloths with various solvents such asBrushes/dusters• acetoneChamois cloths• ethanolCompressed air• tolueneMicrofibre cloths• water (distilled)Sticky rollersCommercial PMMA cleaners WipesCommercial glass cleaners Further testing is being conducted to find methods to either polish outshallow scratches, or to fill deeper scratches in the PMMA surface. Ideally theresults must be invisible. Over 20 commercially available polishing compoundsand filler materials are being tested. The results are being evaluated using visual examination, optical microscopy,and surface roughness measurements. The latter are particularly useful forquantifying changes in the surface of PMMA. The roughness of commercialPMMA sheets lies in the sub-micron range, and many of the initial changes may thus be invisible to the naked eye. Non-contact methods such as interferometry and confocal white light profilometry can provide quantitative informationabout surface roughness changes at resolutions down to several nanometres(e.g. Lange, Jennings and Shah 1993, Wei, De Tagle and Hummelen 2005). The results of specific cleaning, polishing, and filling tests are or will bereported separately (see, e.g. Murphy 2004). These results do, however, show a number of general trends. • Dry cleaning methods scratch the surface of PMMA to some extent,mostly in the form of fine, shallow scratches (see Figure 3). (Zorn 2004,Murphy 2004, Grieten 2005, Casella, Kim, Moore and Kennedy 2007).Scratching is generally only visible under specific lighting conditions in theoptical microscope. Occasional deep scratches were observed for almostall dry cleaning methods, see arrows in Figure 3. After several cleanings,scratching becomes more obvious to the naked eye for the less suitablemethods. Interferometric roughness measurements confirm this, as well asfor less aggressive methods (Grieten 2005). More deep scratches are seen,especially when cleaning cloths are reused. This could be due to embeddedparticles, or new particles which land on the PMMA between cleaning.•A number of wet cleaning methods appear to improve the performanceof dry cleaning materials, reducing the amount of scratching (Grieten Figure 2. Examples of surface contamination, damage, and “ageing” of  face-mounted photographs (a) Evidence of bubble wrap (encircled); (b) Scratching and abrasion (encircled); (c) Local discolouration (arrow); (d) Delamination of the PMMA sheet (arrows)(a)(b)(c)(d)  2005, Casella, Koning, Moore and Kennedy 2007). This may be due tothe lubricating effect of the liquids used. However, many of the liquidstend to streak upon drying, and the occasional deep scratch was stillobserved.•Experiments on filling scratches have not been successful (Zorn 2004,Koseki and Mustardo 2004, Grieten 2005), although some materials andmethods show promise (Kim and Breitung 2007). Filled scratches alwaysremain somewhat visible, even if the filling material has approximately thesame refractive index as PMMA. This could be due to (internal) reflectionfrom the surface of the scratch itself or the filler, and the visibility of theedge of the filled area. The handling and application of the filling materialsis also a problem.•Theoretically, polishing will always change the surface of the PMMA, nomatter what the material or method, since polishing materials have particlesizes which exceed the surface roughness of the sheet. However, somepromising results have been obtained (Breitung and Stenman 2007).  Ageing of face-mounted photographs  While little evidence of long-term ageing of photographs in museums orgalleries has been found, initial accelerated aging studies indicate that face-mounted photographs do discolour.•Zorn (2004) has shown that chromogenic photographs face-mountedusing the Diasec® method discolour faster than unmounted photographsin 4000 K white light. The magenta and yellow dyes are most affectedafter 100 MLux hours. However, inkjet prints mounted the same way donot discolour faster than their unmounted counterparts.•The Museum of Modern Art in New York reports changes to face-mounted samples during natural light aging (Daffner and Barro 2007).Initial results are still within the range of measurement error, but show atendency towards darkening. Unmounted photographs show possiblefading of the cyan dye.•Dark aging tests conducted over two years at temperatures between50 °C and 85 °C, and 50% RH, also show slight discolouration of Diasec®photographs (Jürgens 2001, Wei, Van Bommel and Pouilley 2007). Thecyan dye fades, resulting in a shift in the colour balance towards red/magenta. This effect was evident in an actual face-mounted photograph, which showed slight reddening near the edges.•Initial accelerated ageing tests indicate that there may be long-term effectsof the acetic acid released by the silicone-based sealant. Crazing wasobserved for PMMA stored in acetic acid vapour at room temperatureand 50 °C, though the partial pressure was unrealistically high for thesefirst experiments (Wei, Van Bommel and Pouilley 2007). The fact thatdiscolouration appears near   the edge of the face-mounted photographdescribed above, but not at   the edge, indicates that a combination of acetic acid and oxidation may accelerate the ageing process observed inthe middle of the photograph. Acetic acid readily escapes from the edges,but oxygen also enters easily there. If both contribute to the near-edgediscolouration, this would first occur some distance from the edge. It hasalso been shown that the release of acetic acid is strongly temperaturedependent. Virtually all acetic acid is released within two months at 50 °C, whereas acetic acid was still detected for specimens held at roomtemperature or 3 °C months later. Discussion  The results of initial work on the conservation of face-mounted photographsindicate that there are indeed a number of concerns specific to this type of object which must be addressed. The treatment of the PMMA sheet certainly  Figure 3. Damage due to (dry) cleaning of PMMA: fine scratching, and deepscratches (arrows) probably due to hard  particles  668 ICOM C OMMITTEE   FOR   C ONSERVATION , 2008V  OL II  V  OL IIPhotographic materials 669presents difficulties. Virtually, all cleaning and scratch removal methodsdamage the surface to some extent. This therefore raises the ethical questionof whether treatments must really be “invisible”, or that a certain amount of damage is acceptable. For example, many face-mounted photographs containonly sporadic surface contamination which is not at all obvious unless observedat a raking angle. If proper care of such objects is ensured in the future, itmay not be necessary to treat that damage. On the other hand, if treatment isrequired, it should be as local, reversible and non-invasive as possible. Accelerated ageing tests also show that face-mounted photographsdiscolour. It is not yet known if the mechanism of aging is the same as forunmounted photographs. The network partners thus currently recommend aconservative approach to the preservation and treatment of face-mountedphotographs.1.Preventive measures taken to prevent damage have precedence over allactive treatment methods. The need for good storage procedures andpractices, quality materials and handling is fundamental. Cool storage suchas for unmounted photographs is a possible option for storing face-mounted photographs. Although it may keep the acetic acid in the systemlonger, it would significantly slow all thermally activated ageing effects.2.Cleaning should be conducted as little as possible. Specific cleaning methods cannot as yet be recommended in a review publication of thistype. However, in general, dusting should be performed before any othercleaning steps, preferably using a non-contact method such as the use of an air bulb. For subsequent cleaning, only fresh, new materials should beused, and the cleaning motion should be in one direction and made only once.3.For more stubborn surface contamination, cleaning should only be local. Avoid cleaning solutions which are known to be aggressive to PMMA.4.For handling, use gloves to avoid fingerprints, and care should be taken toavoid scratches, abrasion, and hard impact.5.For transport, wrapping face-mounted photographs is not recommended. The Museum of Modern Art has developed a special case in which thephotograph is suspended or placed in a pressure-fit crate (Murphy,Daffner 2004).6.For display, guidelines for unmounted photographs should be followedfor their face-mounted counterparts until further research indicatesotherwise.Clearly, more research is required, and the network partners welcome allcomments, suggestions, and new participants. Conclusions  An international network of conservators and conservation scientists iscarrying out research to augment and further develop sound guidelines forthe conservation and restoration of face-mounted photographs. Experimental work is being conducted to determine the effect of surface treatments on thecondition of the PMMA sheet used for face-mounting. Studies are also being conducted on the aging of such objects, and how that compares tounmounted photographs. The initial results show that there are specific issues which must beconsidered in the treatment of face-mounted photographs. A conservativeapproach is recommended; in fact, given the relative young age of suchobjects, the focus at the moment should be more on preservation anddamage prevention. In particular, care must be used with any method usedfor cleaning the PMMA sheet in order to keep additional surface damage toan “acceptable” minimum. Face-mounted photographs should be displayedunder conditions suited for unmounted photographs, but it is not yet clearhow such photographs should be stored. Cold storage will slow aging processes, but may present problems for such laminated packages. Further
Advertisement
Related Documents
View more
Related Search
We Need Your Support
Thank you for visiting our website and your interest in our free products and services. We are nonprofit website to share and download documents. To the running of this website, we need your help to support us.

Thanks to everyone for your continued support.

No, Thanks