Author: Paige Schmidt

The presentation by William P. Brown and Dr. Adele De Cruz was an awe inspiring glimpse at the future of conservation. Through the collaboration of the North Carolina Museum of Art and conservation scientists from the University of Pisa and Duke University, an intractable layer of cross-linked drying oil, animal glues, and pigmented varnish was removed from the surface of Spanish painter Lluis Borrassa’s panel painting, Christ Before Pilate, 1420-25.
The painting, which had not been exhibited for over 40 years, was the victim of previous cleaning and coating campaigns, and several layers of consolidation materials and paints and glazes had been applied to the blue passages of Christ’s robe. As a result of the cross-linking of these consolidants and the dark pigmentation of a conealing varnish layer, Christs’s robe appeared almost black.
During treatment at the North Carolina Museum of Art, solvents were successful in removing the toned varnish from the painting. However, the reduction of the complex layer of intractable material covering Christ’s robe (the abstract describes this as a composite of old consolidant, cross-linked drying oil, and restoration materials) was not so straighforward. Conservation scientists (from the aforementioned institutions) used FTIR, SEM, and GC-MS analysis to identify the components of the intractable layer and to discern them from original material, which consistsed of lapis, indigo, and orpiment pigments in egg tempera and glue or bee pollen.
Dr. De Cruz took the podium at this point in the talk to describe the methods used to reduce the intractable composite material. Essentially, laser ablation was employed, which before this talk I was only familiar with in the context of dentistry. I have to admit that my intitial reaction to hearing the terms ‘laser’ and ‘art conservation’ used together might have been a wary one, but a refamiliarzing with the techniques involved with laser ablation (and recalling the established use of this technique on the delicate enamel surfaces of our teeth) was an encouraging and exciting reminder of the vast potential of interdisiplanary approaches to art conservation.
Dr. De Cruz explained that the 2940 nm  Er:YAG (erbium) operates using an intense monochromatic wave of light (2.94 microwatts) at 15 pulses per second to vaporize the intractable material. The depth of penetration is very controllable, maintaining a shallow depth of penetration between 3-5 microns. This light pulse is highly absorbed by water, and produced a near instantaneous steam distillation. A glass cover slip is placed over the dirt, varnish, and paint layer. The laser is used to break up the intractable surface, which is ejected and contained by the glass cover slip. The debris is then swabbed from the surface of the painting and can be used for analysis.
There are several immediately obvious benefits to this method. It eliminates the need for toxic solvents, it allows for a highly controllable and low shallow depth of penetration. There is also no risk of chemical change to the substrate, and the reaction is low temperature.
Dr. De Cruz went in to incredible depth during this talk, and I realize that my summary only touches on the ammount of information she provided. I was furiously scribbling notes the entire time, and certainly wished I had a camera to take photos of her slides. I certainly look forward to hearing more about this topic in the future, and am excited for the future and ongoing collaboration of conservation and science.

As a conservation student entering my first year of graduate study this fall, I was at first intimidated by the topic at hand and the thought of relaying this information to the conservation community, potentially including research scientists, techs, and seasoned conservators who may have a jump-start on understanding these concepts, their implementation, and design execution. However, Paolo Dionisi Vici’s presentation not only made the material pertinent and compelling, but also accessible to a layman like myself. I only hope I can do justice to the complexities of the issue.
The talk abstract provides a great summary as to the ‘why’ of hygromechanical monitoring of panel paintings. Mathematical models and theoretical systems regarding the short and long term effects of environmental conditions on objects need to be substantiated by real life data sets in order to move forward with our understanding of the impact of microclimates (and their fluctuations) on objects. This topic is in direct diologue with the conference theme, Conscientious Conservation: Sustainable Choices in Collection Care, and harkens back to the opening session talks broadly titled Exploring Sustainable Preservation Environments, in which the generally accepted environmental paramaters of the museum were discussed, questioned, and even at times directly challenged. Data-logging by experimental measures, as exemplified by Vici’s talk, is paramount to the future of this conversation.
Vici posed an excellent question at the beginning of his talk by asking “What does stability really mean?” As an example of the potential complexity of this issue, he refered to the localized monitoring of one of the viking ships in Oslo, in which different data responses were logged based on the instrumentations’ location on the ship. The abstract aptly states, “Due to the specificity of each artwork… the analysis of an artifact’s response… can supply useful information about its “individual” sensitivity to the exhibition microclimate….” As the viking ship demonstrates, the complexity of individual responses can even vary within a single (albeit enormous in this case) object.
Now to get to the nitty gritty of the talk, and the part where I formally apologize for my unavoidable oversimplication (of what I suspect Vici already drastically simplified) of the sophisticated instrumentation used to monitor panel paintings. I should mention that while this instrumentation can be used to monitor a variety of wooden objects (such as the viking ship), the abstract notes that “panel paintings are useful in representing the complexity of possible reactions.”
The system of monitoring, the Deformometric Kit (DK), employs two displacement transducers, attached perpendicularly to the grain of the wooden panel. Linear deformations in the panel can be measured based on the proportional change of length of the transducers and subsequent trigonometric calculations. The transducers can be mounted on the back of a panel in different configurations and are not visible while the object is on exhibition.
The DK has undergone several design modifications to improve the specificity of the data being collected and its practicality in a museum context. In earlier models, the transducers were screwed directly into the panels. This complicated the data, because the specifics of what was being measured (surface vs. interior deformations and fluctations) could not be determined. Improvements at the Metroplitan Museum of Art were tested, and the transducers were eventually glued to the surface of the panel. According to Vici, minor shifts in the mounting glue would not negatively reflect the recorded data, because the information being gathered between the two vertical elements reflects general, averaged fluctuations.  A further improvement was made when the base of the system was split, with ‘clips’ being glued to the surface of the panel and the transducers then being attached to these clips, making the transducers removable for transportation of the panel.
Vici provided several examples of the DK in action. Simulations of the potential asymmetry of a panel’s surfaces were conducted by connecting transducers to both sides of test panels. The effects of the movement of moisture as it reached equilibrium within the panel could then be monitored. The data Vici shared with us from these trials spanned hundreds of days, and the applicability of this system’s monitoring to both short and long term condition fluctuations should not go unmentioned. The DK also assisted in inform conservators regarding the appropriate crosspieces needed to provide auxiliary support for a long crack running through The Annunciation, oil on wood, Peter Candid, 1585. The DK was able to assist in determining how rigid the cross pieces needed to be and what kind of connection to the panel would be most appropriate.
I would like to reiterate that Vici did an incredible job engaging the audience with what could have been a very esoteric topic. And, yes, while it could be said that this is AIC, and perhaps only we could be ‘enthusiastic about dust’ (a group of people of which I am proud to be among), I felt the room earnestly abuzz after his talk. One of the most important thoughts that I took away from this talk was the importance of empirical validation of theoretical modeling. It is this sort of empirical validation that will inform our decisions as conservators and museum specialists moving forward with the care of our collections.