Heritage conservation tends to focus on what has been admired for many centuries. Other specialties, such as photographic materials, have only been around for a relatively short period of time. Photography is nonetheless a compelling medium with an array of different processes and variants within them. Research in this field shares the same goals as the one done for other materials: to better understand how, when and where objects were made, what conditions caused them to deteriorate and ultimately how to best preserve them. Studies such as the one presented by Christine Andraud at the AIC-CAC conference aims to bridge the knowledge gap in the field.
As Andraud states in her abstract, color photographs, particularly those classified as chromogenic, lack the kind of study that black and white processes have already received. This is exactly what caught my attention: why is that? Although we are now in the digitally born media age, color photographs have been commercially available since the late 1940s. Until not that long ago, they were the most common type of photographic technique, used by artists and amateurs alike. Today we can find examples of chromogenic prints in fine-art museums as well as in personal archives. Their widespread use is exactly the reason why they should be studied further.
For the purpose of identifying these types of prints analytically, Andraud used fiber optical reflectance spectroscopy (FORS). This is a non-destructive and non-contact technique that has long been used to analyze pigments in paintings. The same technique can also help us in the identification of dyes used in photographic emulsions. Better results are obtained when the device is placed in contact with the sample, but according to Andraud, this doesn’t seem to cause damage.
Dyes used in photography were not always the most chemically stable. In fact, their formulas changed often precisely to change this trend and improve their reliability. The appearance of these photographs can be quite different from the one they had when they were made. Consequently, their visible spectra have almost certainly changed. It is therefore considered more accurate to characterize these dyes in the near infrared region, where the organic functional groups’ fingerprint can more accurately be identified.
Using samples from known manufacturers and dates and the Fischer criterion’s statistical model, the author created a chromogenic processes database, to which other samples of unknown provenance can be compared to. So far, data has been collected for prints made from the 1960s up to the 2000s, by different manufacturers. Kodak samples seem to be the ones that yield better results so far (within 3% error). The author’s goal is to continue this project by analyzing more samples (particularly produced in the 1950s to 1970s) and therefore increase the accuracy of the obtained results.
This method seems to be very promising and I personally hope to hear about it again in the future.
Category: Research and Technical Studies
Posts on research, materials & techniques used in and by conservators
44th Annual Meeting – Research and Technical Studies Session, May 16, "Looking Closer, Seeing More: Recent Developments in the Technical Documentation of Paintings", by Ron Spronk
In the morning session on May 16th, Ron Spronk, Professor of Art History in the Art Conservation Program at Queen’s University, shared his experiences with several recent endeavors to standardize the technical documentation of paintings and to make the resulting information both accessible and user-friendly.
Followers of the Rembrandt Research Project will be familiar with the missions of the projects Spronk describes in that they each generally aim to comprehensively study the oeuvre of a single artist. However, the crucial difference is that the more recent ventures are web-based, open-access, and shareable, and they are highly reliant on the compilation and comparison of images obtained using consistent methods across institutional boundaries.
Spronk spoke first about Closer to Van Eyck: Rediscovering the Ghent Altarpiece, an initiative made possible through the partnership of many organizations, including the Royal Institute for Cultural Heritage (KIK/IRPA), the Getty Foundation, and the Netherlands Organisation for Scientific Research. During the presentation, Spronk briefly toured the audience through the website, which is beautifully user-friendly and self-explanatory. Definitions are available for each of the analytical techniques used, and it is also possible to download condition, materials research, and dendrochronology reports.
The follow-up website, Even Closer to Van Eyck, is set to launch shortly and will focus more on the treatment of the altarpiece. As the Getty Foundation website pronounces, “This second phase of the Van Eyck project will incorporate high-resolution images produced during and after the full conservation of the altarpiece, which is currently underway. The web application is expected to set new standards for digital projects related to art history and conservation by providing access to the decision-making process for the treatment of the altarpiece and by disseminating the open-source technology behind the website to the museum community.” Another extension of the Closer to Van Eyck website is VERONA, or Van Eyck Research in OpeN Access, which has aimed to study and document all paintings securely attributed to Van Eyck in a standardized manner. The resulting scholarship will be published online.
The Bosch Research and Conservation Project similarly attempts to consistently document the entire oeuvre of Hieronymus Bosch and includes restoration of nine works. Several structural treatments were supported by the Getty Panel Painting Initiative. The Bosch website shows three works represented by high-resolution photographs in normal light, infrared images, and X-radiographs, with a three-pane slider moving between them. Spronk described the method by which all of the images were obtained using a window frame, which lets the camera remain completely parallel, and showed a video demonstrating the documentation process. A larger website application is set to be launched at an indeterminate date.
Although not covered during the presentation, the abstract also lists the “Hand of the Master on panels by Pieter Bruegel the Elder,” a comprehensive workshop on Bruegel that took place at the Kunsthistorisches Museum in Vienna from November 24-25, 2015. The workshop program and a presentation by Angela Cerasuolo on The Parable of the Blind and The Misanthrope in the Museo Nazionale di Capodimonte, Naples may be found on Academia.edu.
In searching for these websites after Spronk’s presentation, it became clear that these projects are all very much in progress, and only partial information is, as of yet, available. However, these endeavors appear to be extremely promising. The Even Closer to Van Eyck website in particular is eagerly anticipated because it will share the methodology used to treat the altarpiece. Much as the altarpiece during treatment is itself on display, this website should set a new precedent for transparency and should further raise public awareness of conservation activities. The founding concept of comprehensive, standardized, and open-access documentation on which these projects are based presents an encouraging model that will hopefully one day become more common practice, providing greater opportunities for interdisciplinary research and collaboration.
AIC 44th Annual Meeting – Paintings Session, May 15, “The Painting Materials and Techniques of J.E.H. MacDonald: Oil Sketches from 1909-1922” presented by Kate Helwig, Senior Conservation Scientist at CCI, and Alison Douglas, Conservator at the McMichael Canadian Art Collection
Conservation scientists at the Canadian Conservation Institute (CCI) continue to examine artists’ works and contribute each year to the growing database of information on Canadian artists’ working methods and materials.
One of their latest projects is the characterization of the materials used by painter J.E.H. MacDonald (1873-1932). The study looks at the supports, grounds and paint formulations MacDonald used during the period 1909-1922. This study compliments an important retrospective of the artist’s work planned for 2018 at the McMichael Collection of Canadian Art.
MacDonald was a founding member of the famed cohort of Canadian landscape painters known as the Group of Seven, and was closely associated with the celebrated painters, Lawren Harris and Tom Thomson
In all, 32 works from Ontario museum collections were examined, comprising 11 oil paintings and 21 oil sketches. The goal of this study is to gain a better understanding of the artist’s working methods and materials, and to assemble some reference data to help attribute works of uncertain date or origin. This particular presentation focused on observations and results from 13 of these works.
Throughout the period under study, MacDonald used a variety of rigid painting supports, including fiberboard, pulpboard, laminated pulpboard, and thin bookbinder’s board, which may have been his preferred support.
The study reveals that there was a shift in the size of the support he favoured through this period. Early works before 1914 were varied in size, often small, less than 7 x 9 inches. Through the years 1914-1917, he often chose a standard 8 x 10 inch format, and after 1918 he chose a slightly larger size, 8.5 x 10.5 inches, which was also the size favoured by his friend Tom Thomson, who died mysteriously in 1917.
This change in size of the support was also paralleled by a gradual change in his preparatory layers and painting technique. A variety of materials were found in the grounds of his early works. Sometimes he employed coloured double grounds. After 1918, he abandoned traditional grounds, preferring simply to seal the board surfaces with shellac. It was noted that this layer could prove to be solvent-sensitive during future varnish removal operations.
There was a gradual shift in his painting technique as well: his palette changed from muted colours, layered wet into wet, to a bolder paint application. By 1918 in his Algoma paintings, the brushstrokes are more confident and vigorous, often applied using complimentary-coloured paint strokes. An interesting feature of these works is the fact he often left the support or underlayers visible at the edges of his brushstrokes. Bold outlines of oil paint underdrawing are also sometimes seen through the brush strokes of the upper layers of paint.
Paint pigments and fillers were also characterized for the paintings and sketches studied. MacDonald’s paints were generally complex mixtures made of multiple colours, composed of 2 or 3 main colours, adjusted by the presence of small amounts of 2 or 3 more colours. A distinguishing element of his favoured palette include a characteristic mixture of lead sulfate and zinc oxide for his whites – a mixture that was commonly used by Tom Thomson and members of the Group of Seven. This particular white is likely the new “Flake White” paint manufactured by the renowned British colourmen, Madderton & Co. (founded by A.P. Laurie) used for its Cambridge Colours paints that were sold worldwide in the first three decades of the 20th century. Viridian was the only truly green pigment the artist used, while various blues and yellows were also combined to make other shades of green. Yellows, blacks, reds and blues were also characterized. Of interest is the bright yellow paint, likely a Winsor and Newton tube paint, since it contained chrome yellow and a magnesium carbonate filler, materials not found together in the Cambridge paints line.
The publication of this information on MacDonald’s materials will be a welcome contribution to the advancement of our knowledge of the artist’s working methods. This information will also be essential as scientists begin to examine and ponder the materials used in a controversial group of small oil sketches that were purportedly buried for decades on the artist’s estate, before they finally entered (in recent months) the collection of a major Canadian institution. Tip of the iceberg indeed…
44th Annual Meeting- Joint Photographic Materials + Research and Technical Studies Session- Surface Roughness, Appearance and Identification of AGFA-Gevaert Photograph Samples- by Dr. W. Wei and Sanneke Stigter
Having encountered some very bizarre textures in matte Gevaluxe prints during a National Portrait Gallery internship several years ago, I was eager to learn more about the characterization of these interesting papers. The popular Gevaluxe papers (made by Belgian company Gevaert) often had a velvety matte appearance that was desired by many mid-twentieth century photographers.
This project was inspired by a concern that the increasing reliance of museums on digital surrogates for original photographs might not capture all of the original properties of the photograph. Even where a traditional silver-gelatin or chromogenic photograph has been used as a surrogate, the textured surface of the replacement paper might not match the original. The work Hoe Hoeker Hoe Platter by Dutch artist Ger Van Elk was used as an example of a mixed media photographic work where texture played an important role in conservation decisions. Texture can influence the perception of color, so it was important to characterize the essential properties of the paper’s texture.
Paul Messier’s research was considered an important first step, but Bill Wei’s research team in the Netherlands sought to leverage some of the technology from other industries where surface texture and roughness are systematically quantified (such as the auto industry). First, Wei gave an overview of some of the techniques employed in texture measurement: polynomial texture mapping and confocal white light profilometry. In this project, confocal white light profilometry was used to create a non-contact contour map with a resolution of 60 nanometers. Gloss measurements were also used; on a matte surface the difference between incident and reflected light is the light scattered, so the glossiness (or lack thereof) can be quantified.
The study compared human perception with quantitative texture measurements in observations of textured paper and their apparent roughness or smoothness. An Agfa-Gevaert sample book from the 1970’s served as the source material. Only three of the samples were color papers, so they were more difficult to evaluate. The 25 samples were categorized into 5 groups. Some of the groups had a “macro” texture of waviness, versus a “micro” texture of roughness on a much smaller scale. Group 1 was smooth. Group 2 papers had a very fine texture. Papers assigned to Group 3 displayed the fine texturing in the Group 2 papers, combined with a large-scale waviness. Group 4 exhibited the waviness of Group 3, without the fine texture. Group 5, which included some of the color papers, was comprised of a very regular pattern of raised circular nubs or dots. For anyone who has a lot of family photos from the 1970’s, that dot texture will seem quite familiar.
The research is ongoing, so the presenter mentioned some preliminary observations, without drawing any conclusions. There was not a direct relationship between roughness and gloss. For example, samples from Groups 4 and 5 were just behind group 1 in gloss. The human observers demonstrated that their perceptions of smoothness did not always correlate with the quantitative measurements, especially for some papers in Group 2. It will be interesting to hear the follow-up results as the research team continues the project.
44th Annual Meeting – Research and Technical Studies, May 17, "Characterizing the Age of Ancient Egyptian Manuscripts through micro-Raman Spectroscopy" by Sarah Goler
This is another session that I tweeted (@taradkennedy), so not a long post, but enough to give you the gist at least.
Ms. Goler was using micro-Raman spectroscopy for dating of Egyptian manuscript material.This is super cool because normally we’d have to take a sample of a manuscript and do carbon dating in order to determine a date of an unknown. With this method, we don’t!
So, how does it work? Essentially measurements are taken of the carbon black ink on a particular manuscript using micro-Raman spectroscopy. Using the difference in the dominant peak heights in the spectrograph with ink samples where the date is known, ratios are plotted and graphed to show dates:
So, the more plots you have, the more dates you have; and the more dates you have, the easier it is to determine the date range of an unknown manuscript.
To test that this would work, Ms. Goler analyzed a manuscript where she didn’t know the date range, but the librarian/ curator did. Using this method, she was able to date the manuscript within a 70 year range!
It was nondestructive in that the energy level of the laser used didn’t “burn up” the ink sample. One of the issues that a conservator from the University of Michigan else mentioned during the Q&A portion was that in order to get the peak response that Ms. Goler got, she would destroy the sample. Since my experience with Raman spectroscopy is zero, I can’t really speculate why Ms. Goler was successful and this other woman from U of M was not.
I did think this is a really promising technique, provided I understood the content correctly. If people have edits or corrections, be sure to comment below!
44th Annual Meeting, May 16, Research and Technical Studies, Visible-Induced Luminescence Imaging: Past, Current and Future Applications in Conservation Research, Dawn Kriss and Anna Serotta
I was excited to see the most recent update on VIL imaging as it is an accessible imaging technique that can be used to localize pigments with specific characteristics. It is useful for anyone interested in painted surfaces, and can be used in conjunction with other multispectral imaging, or as a standalone technique.
The basic idea is that you need a light source to produce visible light, a camera with its infrared filter removed, and a bandpass filter to limit the type of light that gets to the camera sensor, along with some standards to help process the images. The pigment particles on the object are excited in the visible range, and emit infrared radiation which is detected by the modified camera. This technique can be used to detect trace remains of pigments that are all but undetectable to the naked eye. The technique was developed by scientists from the British Museum and the Courtauld Institute (see Verri et al., 2009) [1].
In the case studies shown in Dawn and Anna’s presentation the focus was on Egyptian blue, which produces luminescence in the infrared (~910nm) when exposed to visible light. Optimizing the capture and processing protocols will mean better results and hopefully, a means of standardizing and sharing information between conservators working in different labs. While VIL is gaining popularity as more museums add it to their workflow (for example. as part of the APPEAR project spearheaded by the Getty), the technique is still being developed, with much more progress on the horizon. Dawn and Anna reported on results of a survey of VIL users to show where progress has been made and where we can still expect some improvements in the technique.
Capture: varying light sources
There are many options for lights used for excitation, so choosing a light source that is targeted to your research question is critical. As an example, the authors described work by my classmate Brian Castriota showing that red LEDs with an output centered at 630 nm caused greater luminescence of Egyptian blue compared to white LEDs. More research on the luminescence characteristics of other pigments will help users optimize their light sources to target specific pigments.
Processing: calibration, standards, and protocols
While many conservators using VIL use the CHARISMA protocols (developed by the British Museum), others are using Photoshop to process the images. Egyptian blue VIL images are usually shown in monochrome, but as the technique is expanded different overlays or crossfades will help communicate the results by registering the images with other photographs, as Dawn and Anna did for the images shown in their presentation. This is one of the greatest advantages of VIL: it’s very easy to understand the images that are generated and easy to communicate the results to the public. However, capturing good metadata and using appropriate standards are critical for the intercomparability of these data in the future. It will be crucial to develop a luminescence scale or target in order to compare images from institutions who may not be using the exact same capture or processing parameters.
What do we have to look forward to?
While its initial development as a tool for identifying Egyptian blue has led to its popularity among archaeological conservators, it seems like the technique is ripe for more widespread adoption for research into modern pigments, some of which also have unique luminescence properties.
Conservators can use a variety of wavelengths using targeted or tunable light sources (e.g. the CrimeScope, adapted from the forensics field) to survey visible-induced luminescent pigments (other examples of which include dragon’s blood, Indian yellow, Han blue, cadmium red and yellow). Dawn and Anna showed an example of imaging surveying cadmium pigments used in Stuart Davis’s Mellow Pad carried out by their Brooklyn colleague Jessica Ford. For more on the work from the team at the Brooklyn Museum, see their recent blog post here.
Conservators can use a variety of wavelengths using targeted or tunable light sources (e.g. the CrimeScope, adapted from the forensics field) to survey visible-induced luminescent pigments (other examples of which include dragon’s blood, Indian yellow, Han blue, cadmium red and yellow). Dawn and Anna showed an example of imaging surveying cadmium pigments used in Stuart Davis’s Mellow Pad carried out by their Brooklyn colleague Jessica Ford. For more on the work from the team at the Brooklyn Museum, see their recent blog post here.
References.
[1] Verri, Giovanni, et al. “Assyrian Colours: Pigments on a Neo-Assyrian Relief of a Parade Horse.” The British Museum Technical Research Bulletin 3 (2009): 57–62.
44th Annual Meeting – Research and Technical Studies, May 17, "Investigation of Fogging Glass Display Cases at the Royal Ontario Museum" by Helen Coxon et al
This was one of the sessions I tweeted (@taradkennedy), so this won’t be a long post, but I will give you a summary with lots of slide images!
So the problem: these brand-new exhibit cases were mysteriously fogging up for no apparent reason. And even better: once they were cleaned, the fog would roll right in; coming right back like a bad check. Some awesome examples of what was popping up on the inside AND the outside of the glass:
So what was this mysterious fog? Turns out it is a mix of things (it always is): definitely free sodium from the glass along with lactic acid, plasticizers, aromatic hydrocarbons… the digital shots of the GC/MS results are mostly illegible unless you have the peak locations memorized, but I did get a shot of where all of this stuff came from:
So, everything from the air around the cases to the materials that they were cleaned with to the goo that they lubricated big, heavy machines with that moved the glass pieces around like this:
So, now what? Luckily Stephen Koob, King of the Glass Conservators, had a nonionic formula that worked!
Here’s the recipe. I hope you can read it.
Hilariously, the glass manufacturer felt bad and came up with this six-stage cleaning kit for the museum to use. The museum was like… um, thanks, but no thanks. Yeah, not even the fussiest of conservators wants to do that much cleaning.
This talk was one of my favorite talks of the conference: folks presenting a practical problem in an accessible way that was thoroughly researched with a practical (nonionic) solution… SOLUTION, get it???
OK, I’ll stop now.
ECPN spring webinar: Pathways into Conservation Science
The Emerging Conservation Professionals Network (ECPN) is pleased to announce that our next webinar “Pathways into Conservation Science” will take place on Friday, April 22nd from 12-1pm (EST).
The program will feature three speakers: Dr. Tom Learner, Head of Science at the Getty Conservation Institute; Dr. Gregory Smith, the Otto N. Frenzel III Senior Conservation Scientist at the Indianapolis Museum of Art; and Dr. Robyn Hodgkins, the Charles E. Culpeper Fellow in the Scientific Research Department at the National Gallery of Art. The presenters will share their own diverse training experiences, touching on the history of education in conservation science and the current pathways into the field. ECPN hopes that the webinar will provide guidance to individuals considering careers in conservation science, current students and post-doctorates entering the field, as well as inform emerging conservators.
The format of this webinar will be Q&A style. ECPN is seeking question submissions prior to the webinar broadcast. Please submit your questions as comments to this post, or contact ECPN’s Professional Education and Training co-Officer, Elyse Driscoll at elysedriscoll@gmail.com. Questions will be accepted until the morning of the webinar. Selected unanswered questions may be addressed in an AIC blog post following the webinar.
This webinar is free and open to all AIC members but you must register! To register, please click here. You will receive an email with information on how to connect to the webinar shortly before April 22nd.
If you miss “Pathways into Conservation Science” or wish to watch it again later, it will be recorded and uploaded onto the AIC YouTube channel. For a listing of past ECPN webinars, please visit our archive on AIC’s blog Conservators Converse, our Wiki page, or AIC’s YouTube channel.
About the Presenters:
Tom Learner is head of the Science Department at the Getty Conservation Institute (GCI); he oversees all of the Institute’s scientific research, developing and implementing projects that advance conservation practice in the visual arts. As a GCI senior scientist from 2007 to 2013, he oversaw the Modern and Contemporary Art Research initiative, during which time he developed an international research agenda related to the conservation of modern paints, plastics, and contemporary outdoor sculpture. Before this, he served as a senior conservation scientist at Tate, London, where he developed Tate’s analytical and research strategies for modern materials and led the Modern Paints project in collaboration with the GCI and National Gallery of Art in Washington DC. Dr. Learner holds a PhD in chemistry from Birkbeck College, University of London, and a diploma in the conservation of easel paintings from the Courtauld Institute of Art.
Dr. Gregory Dale Smith received a B.S. degree from Centre College of Kentucky in anthropology/sociology and chemistry before pursuing graduate studies at Duke University, where he was as a National Science Foundation graduate fellow in time-domain vibrational spectroscopy and archaeological fieldwork. He held postgraduate positions at the British Library, the V & A Museum, the National Synchrotron Light Source, and the National Gallery of Art. In 2004, Dr. Smith joined the faculty of the conservation training program at Buffalo State College as the Andrew W. Mellon Assistant Professor of Conservation Science. In 2010, Dr. Smith was hired as the Otto N. Frenzel III Senior Conservation Scientist at the Indianapolis Museum of Art where he established and now operates a state-of-the-art research facility to study and preserve the museum’s encyclopedic collection. Dr. Smith’s research interests include undergraduate education at the Arts-Science interface, assessing pollution off-gassing of museum construction materials, and understanding the chemical degradation of artists’ materials. Greg is a Professional Associate of the AIC and has served as an associate editor of JAIC for the past 10 years.
Dr. Robyn Hodgkins is the Charles E. Culpeper Fellow in the Scientific Research Department at the National Gallery of Art (NGA), Washington, DC. She received her PhD in Chemistry from the University of California, Los Angeles. Before starting at the NGA, Dr. Hodgkins completed a conservation science internship at Tate Britain, and conservation science fellowships at the Metropolitan Museum of Art, the Smithsonian’s National Museum of the American Indian, and the Smithsonian’s Museum Conservation Institute. Dr. Hodgkins’ interests include understanding the effect of environmental conditions and pollutants on museum objects and artists’ materials using corrosion studies and environmental monitoring, and developing methods for the identification of paint constituents.
CENIM-CSIC Research Group seeks to survey Professionals
We are a research group from the CENIM-CSIC and we are carrying out a study about the methods of cleaning and protection of historical lead.
As part of this study, we want to know the methods more applied by professionals and their personal experience about them.
The survey should take 10-15 minutes and it is available in the next link. Please feel free to pass it on.
<URL:http://goo.gl/forms/80sJsl3Nx9>
If you are interested in the results, please leave your email in the section of contact details. If you want more information, please feel free to contact me at t.palomar@csic.es. Thank you in advance for your collaboration.
Dr. Teresa Palomar Sanz
Centro Nacional de Investigaciones Metalalurgicas (CENIM) Consejo Superior de Investigaciones Cientaficas (CSIC)
Survey on methods for cleaning and protecting historical lead
A research team from the National Center for Metallurgical Research (CENIM-CSIC) is carrying out a study about the methods of cleaning and protection of historical lead. As part of this study, the investigators hope to learn about the methods applied by professionals and their personal experience with them. The survey should take 10-15 minutes and it is available until July 15th at: http://goo.gl/forms/80sJsl3Nx9 Please feel free to forward the link to interested colleagues.
The results will be published afterwards, and will be sent to interested participants. To receive results, please leave your email in the contact details section of the survey. For more information about this study, please contact t.palomar@csic.es. Thank you in advance for your collaboration.
Dr. Teresa Palomar Sanz
Centro Nacional de Investigaciones Metalurgicas (CENIM) Consejo Superior de Investigaciones Cientificas (CSIC) Avenida Gregorio del Amo, 8.
28040 Madrid
Spain