Tag: conservation science

45th Annual Meeting – Workshop, May, 29, 2017, “Effectively Using Portable IR and Raman Instruments for Art Object Analysis,” presented by Francesca Casadio and Tom Tague

My personal area of interest and intended future practice is in the conservation of historic interiors. Therefore, I am always keen on portability both in tools and materials as well as forms of analysis. The other advantage to the techniques presented in this workshop is that physical sampling is not required, which is always attractive and music to a curator’s ears.

The workshop met my personal expectations, but the title “Effectively Using…” could have suggested to some that this was going to be more of a “boot camp” for being able to implement these techniques back home. This style of workshop was more of an information/demonstration session and is great for anyone considering buying similar instrumentation and/or for gaining a better understanding of the general benefits and limitations of portable spectroscopy.

Given the short duration of this workshop, I was initially concerned that I might have signed up for a 2 ½ hour lecture without any hands-on component. Participants were encouraged to bring our own samples and indeed at least an hour was dedicated to looking at samples and exploring the instrumentation first-hand. Although we did run over the scheduled time, and were gently shuffled out of the room as hotel staff started to break down tables.

The workshop was led by Tom Tague, Ph.D. Applications Manager at Bruker, and Dr. Francesca Casadio, Director of the Conservation Science department at the Art Institute of Chicago. I really appreciated having these different perspectives. Tague did not assume the role of salesperson during the workshop, but as you would expect he was very positive in his description of the capabilities of the Bruker instrumentation. Casadio kept Tague grounded in the realities of our complex samples and what can be confidently identified using these techniques. At the same time, it was useful to have Tague there to speak to the specifics of the instrumentation and push Casadio a little bit to consider what some of the newer technology could offer. There was also a Bruker sales representative present to assist with running the instrumentation and software and offer information on pricing.

Overall the session was well organized. I know I was not the only attendee who was ecstatic that I got to take home a flash drive loaded with the presenters’ PowerPoint slides. The spectra from my samples that were analyzed were also loaded directly onto this flash drive before the end of the workshop.

The first part of the session did consist of pure lecture. Tague’s presentation focused on specifications of the Bruker portable instruments and descriptions of the techniques.

An interesting tip he offered was using sandpaper to take surface samples. He lightly abraded a painted surface and then placed the sandpaper in front of the portable FTIR (ALPHA)—no additional sample prep necessary.

Having just completed my Master’s degree in conservation I was able to follow the presentation fairly well, but I fear that it may have been overly technical and too fast for someone who does not work with these analytical techniques on a regular basis. Nonetheless, I anticipated this to be an intermediate-level workshop when I signed-up.

Tom Tague in front of demo table at the workshop. He has rotated the ALPHA in front of him so that the laser beam points downward and is working to raise the ALPHA up on some shims in order to fit the sample under the beam at the correct working distance.

 

As would be expected based on the organizers of the workshop, the instrumentation provided and discussed were all Bruker models. Two ALPHA portable FTIR spectrometers were present. The ALPHA is set up to receive different “snap-on” modules. The two modules available for demonstration were the “External Reflectance” module and the “Platinum ATR” module. The BRAVO Handheld Raman spectrometer was also available for interaction.

 

Here are some key facts about each instrument:

 

The base ALPHA starts around $14,000 and each module is on average $6,000 in addition.

 

 

 

ALPHA “External Reflectance”

  • Does not require direct contact with a sample/object
  • No size limitations as long as unit can be mounted/held in appropriate orientation to the sample

    ALPHA “External Reflectance” being used to analyze paper currency. This example was given in Tom Tague’s presentation.
  • Camera integrated in unit to help orient, find appropriate working distance/focus, and document sample location
  • Collects reflectance spectrum NOT absorbance
    • Can collect specular and diffuse reflection; reflective and non-reflective materials can be analyzed
  • Footprint of instrument is about 8” X 11”
  • Weighs about 13lbs.
  • Can be tethered to a laptop
  • About 6mm sampling area
  • Approximately 4cm-1 spectral resolution

ALPHA “Platinum ATR”

  • There is pressure/direct contact with the sample
  • The IR beam does penetrate into the sample

BRAVO Handheld Raman

  • $45,000-$55,000
  • Slightly narrower than 8” X 11” (looks like an oversized ELSEC environmental data monitor; less heavy than the Alpha)
  • Class I safe laser
  • 2mm sampling spot size
    • No camera or viewing capability to help align collection area
  • Object needs to be in contact, but no pressure required
  • Approximately 8cm-1 spectral resolution
  • Fluorescence mitigation built into software/data collection
  • Dual lasers built in and used/activated simultaneously
    • Optimal wavelength and reduced risk of damaging sample
  • Touch screen allows for control and data collection without tethering to laptop
    • Tethering also capable via WiFi to laptop
Example from Tom Tague’s presentation of the BRAVO being used to analyze medieval manuscripts at the Morgan Library and Museum.

 

In terms of the ALPHA “External Reflectance” one of the big selling points is that there is no size restriction or need to balance the object on a stage. The trade-off in allowing data collection without physical sampling is that the spectra generated are in % reflectance. The majority of reference spectra available for free and through the Infrared and Raman Users Group (IRUG) are % absorbance or % transmittance (its inverse). The Bruker software does offer the capability to convert the data using the Kramers-Kronig Transformation. Francesca Casadio seemed to prefer to analyze data from its original state in reflectance. Characteristic peaks for bonds are slightly shifted from their location in transmittance spectra, but at Casadio’s level of experience she is able to take these nuances into account with some ease. She was honest with the attendees summarizing that this form of IR spectroscopy is “not like portable XRF; one needs to have experience and repetition for familiarity with interpreting spectra.”

For those interested in more on interpreting reflectance spectra of art objects Casadio recommended the following publications from a research group in Perugia Italy:

“Reflection infrared spectroscopy for the non-invasive in situ study of artists’ pigments.” C. Miliani, F. Rosi, A. Daveri & B. Brunetti, Appl. Phys. Mater. Sci. Process. 106, 295–307 (2012) (http://dx.doi.org/10.1007/s00339-011-6708-2)
“In Situ Noninvasive Study of Artworks: The MOLAB Multitechnique Approach.” C. Miliani, F. Rosi, B.G. Brunetti & A. Sgamellotti, Acc. Chem. Res. 43, 728–738 (2010) (http://dx.doi.org/10.1021/ar100010t)
“Non-invasive identification of metal-oxalate complexes on polychrome artwork surfaces by reflection mid-infrared spectroscopy.” L. Monico, F. Rosi, C. Miliani, A. Daveri & B.G. Brunetti, Spectrochim. Acta Part -Mol. Biomol. Spectrosc. 116, 270–280 (2013)
“In-situ identification of copper-based green pigments on paintings and manuscripts by reflection FTIR.” D. Buti, F. Rosi, B.G. Brunetti & C. Miliani, Anal. Bioanal. Chem. 405, 2699–2711 (2013)

 

It is important to keep in mind the basis of data collection to understand the limitations of what can be analyzed with the ALPHA “External Reflectance” on a given object. For example, with a varnished painting the spectral reflectance of the varnish will typically only allow the varnish itself to be detected (with some exceptions depending on thickness of the varnish and underlying pigment composition). Similar reflective material properties make plastics easily detectable with this technique. Matte objects are still good candidates for analysis with the ALPHA, but the data will be collected via diffuse reflection. The ALPHA does not seem like an appropriate technique for discerning between individual layers within a given structure unless coupled with other techniques.

One of the ALPHA’s at the workshop was supplied by Casadio from the Art Institute’s lab, and she has extensive experience using the ALPHA. Her presentation was more about working knowledge of the instrumentation. She polled the attendees and focused on case studies mainly of pigment analysis and identification of plastics. Casadio emphasized the benefit of the ALPHA as a mapping tool that does not require sampling. Perhaps one or two samples could be taken from a work of art and more confidently characterized with bench top FTIR and/or GC-MS and then the use of specific materials could be mapped without additional sampling using the ALPHA. Casadio’s case studies often combined multiple analytical techniques. She finds the ALPHA to be a nice compliment to XRF. Overall, Casadio has found the ALPHA to be very useful in characterizing different plastics and also good at detecting deterioration surface products (e.g. zinc soaps) especially with modern and contemporary collections. Casadio noted that the ALPHA detects very strong signal and peaks for waxes and PVA coatings. Casadio has been able to use the ALPHA for collaborations with other institutions and collections, which is another boon of its portability.

I was disappointed that Casadio had not had previous experience with the BRAVO Handheld Raman. At the Art Institute she has a bench top Raman unit. She seemed skeptical about the BRAVO’s capabilities and some of the claims that Tague was making that it could “see” indigo and other organic pigments without surface enhanced Raman spectroscopy (SERS). Casadio stated that in her personal opinion with Raman it is better to bring the art to the unit than the other way around. By the end of the workshop she did seem impressed with the quality of spectra the BRAVO was generating, but there was not enough time to have further discussion and to tease out Casadio’s candid opinion on the instrument.

I was most excited for the practical demonstration with the instruments especially because I had come armed with over 10 samples. I was anticipating that I may not even get to analyze one sample, but was very pleased that I was able to look at 7 samples with the BRAVO portable Raman. This much time with the instrument was due in part to many participants not bringing samples.

If a similar workshop is organized in the future, it might be good to have participants sign up ahead of time for slots with the instrument if they are interested in analyzing a specific sample. It was a fairly large group – about 18 participants. Attendees that did not bring samples were still interested in watching the process of collecting data and interpreting the spectra. This was challenging; even with three instruments there tended to be 5-7 people crowding around a laptop screen. Dividing us into smaller groups, having the laptops hooked up to a projection screen, or further limiting the number of participants may be additional considerations for future workshops.

It seemed like the majority of participants were conservators rather than conservation scientists. I personally do not work with spectroscopic techniques on a regular enough basis to be able to confidently interpret spectra on the fly. Francesca Casadio was able to offer her expertise and interpretation while working with samples from the participants, but neither Tom Tague nor his Bruker colleague could offer specialized interpretation. Some of the participants seemed frustrated that the instruments were not connected to an art materials database for instant gratification and matching.

Both Tague and Casadio strongly emphasized the importance of each institution building its own reference database specific to the collection. The IRUG database was promoted, but as a supplement to an institution’s own reference database. Neither of the instructors felt that the database that comes with the Bruker software was appropriate for art materials.

My personal goal during the workshop was to pit these portable instruments against their stationary counterparts and to pit the two complimentary techniques against each other. Therefore, I brought known samples from my institution’s reference collection of traditional paints. All the paints were oil-based and mixed with some degree of lead white. The reference pigments I chose were mostly organics (indigo, madder, cochineal). Colonial Williamsburg has had the opportunity to partner with the College of William and Mary in order to perform SERS on objects in the paintings collection. My colleagues and I were curious to see how this portable unit compared to spectra produced with SERS. With the minimal time, I chose to focus on the BRAVO because our institution already has a bench top FTIR.

Tom Tague was set-up at the BRAVO “station” during the practical session, and as I stated previously he was not comfortable offering any interpretation of the data. I was excited to review the spectra we collected back at my home institution (Colonial Williamsburg Foundation/CWF) alongside Kirsten Travers Moffitt, the conservator in charge of our materials analysis lab. Moffitt performs a lot of FTIR analysis on our collection, but has less experience with Raman.

All the organic paint spectra from the BRAVO were certainly “neater” than what I am used to seeing in terms of raw data from a bench top Raman with oil paint samples. I personally would attribute the quality of the spectra to the dual laser capability. I’m not sure how much impact the fluorescence mitigation had because the spectra were still pretty noisy and it was challenging even for Moffitt to distinguish significant peaks. It appears that the fluorescence of an oil binder is still problematic with the BRAVO. In Tague’s presentation he showed an example of indigo detection with the BRAVO, but this was on an illuminated manuscript, where fluorescence of the binding media would be less of an issue.

At CWF we only have a reference database for IR spectra, but looking at possible peaks in the indigo/lead white sample spectrum, the characteristic peaks for indigo that Tague mentioned (545, 1463, 1578) do not appear to be present. It seems that the lead white is dominant, with a strong peak around 1050. In conclusion, Tague is partially right that the BRAVO can detect some organic pigments, but likely only if they are present in high enough concentrations (not mixed) and are not in highly fluorescent binding media (like oil).

Spectra (representing a shorter and longer collection time) from the BRAVO of the CWF reference of indigo and lead white in oil.tic peaks for indigo that Tague mentioned (545, 1463, 1578) do not appear to be present. It seems that the lead white is dominant, with a strong peak around 1050. In conclusion, Tague is partially right that the BRAVO can detect some organic pigments, but likely only if they are present in high enough concentrations (not mixed) and are not in highly fluorescent binding media (like oil).

The other samples I looked at were reproduction wallpaper samples from Adelphi. I was curious to see if we could detect anything useful about the pigments on an object that would normally be challenging to sample and could not be brought to the lab if it were installed in a historic interior.

The resulting spectra were less noisy than those of the oil paint reference samples, again likely due to the non-oil binding medium on the wallpaper.

 

 

Spectra collected from two different greens on a wallpaper reproduction from Adelphi using the Bruker BRAVO. Peaks are labeled, but a match has not been identified.

 

 

Despite the better quality of the spectra, we still did not have the resources (i.e. a good reference database for Raman and experience working with Raman spectra) to confidently characterize the pigments present. I am sharing this to illustrate Casadio’s point that the ALPHA and BRAVO require a certain level of expertise and do not provide instant answers.

One of the other participants, Ann Getts, a textile conservator at the De Young Museum in San Francisco, brought various sequins from a costume in storage with a suspicious vinegar odor. Getts had time to look at one of the sequins with both ALPHA modules, and her case study demonstrates some of the trade-offs with the non-contact “External Reflectance” module.

She began with the “External Reflectance” module and the first hurdle was getting the instrument positioned at the appropriate working distance from the sample. Without an adjustable stand, we had to use trial and error to shim up the ALPHA so that the camera could focus on the sequin. The resulting spectrum suggested cellulose acetate (as suspected by Getts initially), but even Casadio still felt insecure about drawing any concrete conclusions based on this spectrum. Then the sequin was analyzed with the “Platinum ATR” module and right away Casadio concluded that indeed it was cellulose acetate.

Each of these instruments has their advantages and disadvantages. Overall the ALPHA seems like a good bang for your buck given the duality of the modules. The price point is pretty reasonable also considering the portability.

The BRAVO is fairly new technology and the dual lasers seem promising, but at this point it does not seem like a must have for the average institution. I would encourage anyone thinking about purchasing any of these instruments to consult with both of the workshop leaders.

Francesca Casadio using the ALPHA to analyze a Roy Lichtenstein painting installed on the wall.

 

In general I would specifically recommend the ALPHA to:

  • Institutions that have a lot of sampling restrictions
  • Institutions with a lot of oversized works
  • Institutions that focus on modern and contemporary art (especially with plastics and large Color Field paintings)
  • Institutions with a conservation scientist on staff

 

In general I would specifically recommend the BRAVO to:

  • Institutions that have a lot of sampling restrictions
  • Institutions wanting to focus on analysis of paper-based art
  • Institutions with a lot of oversized works
  • Institutions that already have staff with Raman expertise
  • Institutions looking to purchase a Raman instrument

This blog represents my personal conclusions and understanding of the workshop. I would encourage any of the other participants and the instructors to post in the comments if they have differing opinions or think that I have misunderstood any of the technical aspects of the instrumentation.

Joint 44th AIC Annual Meeting and 42nd CAC-ACCR Annual Conference – Research and Technical Studies Session, May 17th – “Ensuring Maximum Impact for Conservation Science” by Marie-Claude Corbeil

Right off the bat, Dr. Corbeil noted that the title of the talk should probably be a question rather than a statement, because nobody has all of the answers, and this talk was not going to be a definitive guide to conservation science. She noted that conservation science still has some issues – it can be very expensive to complete scientific research projects, and thus there is a reliance on government funding, which can be fickle in a number of ways. Through these challenges, Dr. Corbeil’s aim was to show how the CCI operates, raise questions about the efficiency of the approach, and understand how best to ensure maximum impact for conservation science.
The CCI has three main categories of work: research and development, expert services, and knowledge sharing, all of which are interconnected, and which relate to the community that CCI serves. Dr. Corbeil spoke specifically about a number of examples of this work, including dripping paint on works by Alfred Pellan; authentification of works by Jean Paul Riopelle in conjunction with the Getty; fading paint on Rothko murals; and various pesticide surveys of textiles.
Of these cases, the Rothko question had interesting implications. With the Rothko, the institution asked for the analysis to be completed, and result showed the presence of a fugitive pigment. A monitoring program was enacted in response to this. Dr. Corbeil mused on a few topics – was the analysis really necessary, given that many Rothko works have these fugitive pigments? Would the exhibition decision have been different without analysis? Is the monitoring necessary, given that degradation of these fugitive pigments is inevitable?
The pesticide surveys also brought up an interesting chain of discussion, involving the repetition of analysis for different clients. If enough data has already been collected to generate guidelines and predict the results of surveys, is it necessary to continue to analyze separate collections? Dr. Corbeil noted that it has been an inescapable fact that people want to test their own collections, even if previous applicable results are available. This is not necessarily a bad thing, but it also points to the idea that services rendered for one client may be broadly applicable, and that dissemination of results will always be significant.
Dr. Corbeil concluded that the key elements for success involve choosing the right research question, engaging in collaboration, transparency in methodology, and effective dissemination. Within this context, one of her previous statements resonated with me – she stated that results are disseminated “in the traditional way” at CCI. I wonder if there is a benefit to looking into non-traditional routes for the sharing of knowledge, since that is one of the areas Dr. Corbeil indicated was most important for the success of conservation science? I look forward to future discussion of this topic, and the bright future of conservation science as a whole. Keep up the great work, CCI!

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.

41st Annual Meeting – Research & Technical Studies, June 1, “Contemporary Conservation for Contemporary Materials” by Yvonne Shashoua

Attending a lecture by Yvonne Shashoua, Senior Researcher in the Department of Conservation at the National Museum of Denmark, was such a treat, since she is so well-known in the field of plastics conservation, and her session did not disappoint.  Her calm, precise, and very approachable speaking style was impressive as she covered a scientific discussion on her current research into cellulose acetate degradation and its interaction with gas absorbents.  Since she will be presenting her findings in upcoming journals, I will only briefly go over what I learned and what you missed at this Research & Technical Studies AIC session.
Shashoua began by reminding us that plastics comprise an increasing proportion of museum collections.  Since it is difficult to detect plastic degradation until it reaches an advanced stage, a preventative approach, by either removing the factors causing or accelerating degradation, is usually taken.   Gas absorbents (silica gel, activated charcoal, Zeolite 4A, and Corrosion Intercept) are frequently used in museum storage and display situations to create a microclimate by removing specific gases.  She discussed how these materials are used and how they absorb pollutants, which I found very interesting.
Focusing on cellulose acetate, Shashoua discussed the mechanism of degradation (and the breakdown by-product acetic acid) and how additives (plasticizers and fire retardants, which are weakly bonded within the matrix) migrate out ultimately ending in shrinkage.  She was curious why the degradation process even begins in a museum environment, which began her in-depth research project. Cellulose acetate, has been used since 1910, but by the 1960s could be found in many objects: imitation mother of pearl, cigarette filters, early Lego bricks,  movie film bases and rayon.  By conducting a systematic study on the adsorbents’  interaction with cellulose acetate, she has found some startling results.  The adsorbents in some cases did slow down the onset of autocatalysis, however some also adsorbed the plasticizer and/or flame inhibitor, resulting in damage.  Her results suggest that commonly used absorbents in museums are non-specific and ineffective for cellulose acetate and, by extrapolation, other plastics.  She did rate the adsorbents  on a sliding scale; so reading her more in-depth post-prints will be a good lesson and/or review for all of us.  All this is startling news!  An archival acid-free box might simply be the best defense.  Wow.  I cannot wait to read her in-depth post-prints and journal articles concerning this fascinating subject.