Fine Arts Museums of San Francisco Imaging and Conservation Departments

This lecture was presented at the 3D Digital Documentation Summit held July 10-12, 2012 at the Presidio, San Francisco, CA

Applications of Reflectance Transformation Imaging (RTI) in a Fine Arts Museum: Test, Documentation, and Beyond

In 2006, the Worcester Art Museum collaborated with Cultural Heritage Imaging (CHI) to develop reflectance transformation imaging (RTI) as a viable exam and documentation method for fine art collections. This included designing an RTI dome and establishing a digital workflow protocol for acquiring, processing, and storing RTI files. As the start American art museum to integrate RTI into conservation do, the Worcester/CHI collaborators presented their accomplishment at the 2009 Almanac Meeting of the American Institute for Conservation held in Los Angeles. Since then, the Museum has documented the surface topologies of a wide multifariousness of fine art materials, with a particular interest in finding new applications for RTI. This newspaper presents a brief sampling of examples of RTI utilize, with an accent on two unique examples in which the application of RTI went beyond the sole purpose of documentation to raise significantly our understanding of the artistic process.
The first example involves a research project that investigated a group of Greek ruby-figure vases and vase fragments in the collection of the Harvard Art Museums and the Worcester Fine art Museum. The project, which is a continuation of research presented by Worcester at the 2010 MRS conference in Boston, utilized RTI in conjunction with laser scanning confocal microscopy to help resolve a long-standing debate among scholars regarding the technique used to create the characteristic 'relief lines' of the surface ornament. This research also involved mock-ups for comparing to better understand the aboriginal applied science and ultimately led to the conclusion that the relief lines were not produced by an extruded method every bit previously postulated, but with a brush fabricated of 2 or very few hairs, termed linierhaar as first proposed by Gérard Seiterle in 1976. Ii distinct types of relief lines were observed: the laid line (proposed by Seiterle) which has a characteristic ridged profile, and the pulled line (proposed in a previous paper by the authors) which has a furrowed profile. Additionally, it was determined that the relief line used to outline figures was practical prior to the contour line. These findings are primarily based on surface topography evidence visible using RTI.
The 2d example involves the discovery of an original inscription on an early-career portrait by the Flemish Baroque master Anthony Van Dyck (1599-1641). The portrait, which belongs to the Royal Museum of Fine Arts in Antwerp, is of an unknown human being and is on long-term loan to the Worcester Art Museum. Obvious compositional changes to the sitter'southward neckband and groundwork prompted x-radiography and infrared reflectography examinations to evaluate the extent of changes throughout. Neither of these methods revealed the underlying inscription; however, during visual examination at Worcester's conservation department, a faint feature was noticed in the pigment surface topography that suggested the presence of the underlying inscription. The inscription likely was painted over at the aforementioned time modifications were made to the sitter'due south costume. Subsequent awarding of RTI enabled conservators to image the entirety of the previously unknown inscription, which now provides scholars with a firm date for the artist's original limerick and an example of how RTI can yield results where more established imaging techniques such as x-radiography and infrared reflectography do non.

Transcript

Church: Alright, next talk is "Applications of Reflectance Transformation Imaging, RTI, in a Fine Fine art Museum: Examination, Documentation, and Beyond" with Philip Klausmeyer. Philip earned an fine art history and a studio art degree from the University of Massachusetts Amherst, an 1000.S. from the Winterthur University of Delaware Programme in Art Conservation, specializing in paintings. In add-on to 15 years at the Worchester Art Museum, his conservation work includes time at the Strauss Center for Conservation, Harvard Museum of American Art, and Pennsylvania Academy of Fine Arts. He received his PhD from Clark University and is currently a Conservation Scientist and an Acquaintance Paintings Conservator.

Klausmeyer: Thanks Jason, OK, so today, I am speaking non in the capacity of a conservation scientist merely to add my voice to this growing chorus of terminate users and conservators virtually the value and use of RTI in our solar day to solar day practices and its importance in answering defined questions, thus the title today; "Applications of RTI in a Art Museum: Examination, Documentation, and Beyond."

A quick overview of my presentation includes an introduction and so it is divided into two parts, the first part is using RTI to study Greek attic pottery, and the second office is an awarding of RTI in an ongoing conservation handling of an early work by Anthony van Dyck. The last three talks today are from iii conservators from three different institutions, one of which is the Smithsonian, 1 of which is the Metropolitan Museum of Fine art, and and then there is the Worcester Art Museum. So I expect of these three, yous might demand a little bit of an introduction to ane of them.

So the Worcester Art Museum is about an hour drive due west of Boston and information technology is a classic American art museum founded correct effectually the plow of the final century. The museum drove is actually encyclopedic in nature and although it doesn't accept the numbers of the Smithsonian past whatever ways, it's got well over 35,000 objects in its collection representing everything from painting, sculptures, decorative arts, photography, prints, drawings, and more, and ranging from ancient to mod. On the left you see the facade of the 1930's building and on the right you run across a view of our beloved Renaissance Courtroom with its centerpiece, the famous Worcester Hunt Mosaic, which is the largest ancient mosaic in Due north America.

So the Worcester Fine art Museum has a history in conservation that is one that we tin be proud of, and it is cheers in large office to these two gentlemen that you see hither. The conservators in the room will probably recognize George Stout, who'due south pictured on the left; they probably don't know that he was the director of the Worcester Art Museum starting in 1947. He was very instrumental in bringing up the gentleman you see on the right. His name is Edmond de Beaumont and you encounter him working with some land of the art
X-ray equipment from the 1940'due south. Edmund, I really desire to give him props in this talk today considering and so much of what we are talking about is documentation. For all the opportunities I might have to differ in opinion in terms of the conservation treatments that took identify during his tenure, Edmund was an incredible documenter. He left an incredible record of all the things that he did and the value to usa today is really hard to underestimate.

Today, the conservation lab remains a vibrant part of the museum's mission to preserve, collect, and exhibit works. There are two labs to the museum. Pictured here is the main lab that houses our objects, conservation center, and the paintings conservation. On the far left, yous see the head of the section, Primary Conservator Rita Albertson, myself, and on the far right is Birgit Strähle, our assistant paintings conservator. Winifred Murray is shown at the microscopes standing. She is 1 of two Andrew Mellon fellows that we have. We have these rotating positions of fellowships and they are typically a three twelvemonth position and they rotate between specialties of paintings, objects, and paper. In the distance yous volition see Paula Artal-Isbrand who is our objects conservator.

The museum has tried to remain true to its proud heritage of conservation and in 2004, we got the beginning of three grants from the Andrew W. Mellon Foundation and that enabled us to purchase some scientific instrumentation. That included an FTIR spectrometer, an XRF spectrometer, improvements to our existing polarized light microscope, infrared reflectography and what was the original line item was budgeted for a more high-powered X-ray tube. That was really the interest of Lawrence Becker, who some of you might know equally the head of the objects conservation department at the Metropolitan. He was, at that time, head of our department at Worcester.

When Larry left for the Met, and then did the involvement for the high-powered X-ray tube because no ane was going to be carrying out the projection of looking at the statuary sculptures. So we deemed our current Lorad 10-ray tube, which is a Lorad 200, as sufficient for our purposes. I lobbied heavily to re-appropriate that money into the budget for equipment to get towards starting upwardly the museum in what was and then kind of a fledgling applied science of RTI and PTM. That took a lot of letters and reports to Angelica Rudenstine. Some of yous may know her every bit a previous head of the Mellon'south Museum Department. Correspondence could be a very trying thing sometimes with Angelica, only I am glad to say she became a laic in this technology, and and so I went out, and information technology was a fleck of serendipity, just I went to a talk where Tom Malzbender was and merely happened to find myself side by side to him at the dejeuner table. He put me in touch with the squad at Chi, Carla and Mark and it wasn't long before a fantastic collaboration started up. We designed, in 2007, the RTI stock-still light assortment dome that you see here. By 2008 it was installed and we were upward and running with it. And then by 2009, we gave the presentation listed below:
Reflectance Transformation Imaging: A New Conservation Tool for Examination and Documentation.

That was at the 37th Annual Meeting of AIC that was held in L.A. that twelvemonth.    So, since then, we've had time to integrate it into our own workflow and what I am thankful I don't have to talk about today are the principles behind the method. Only what I desire to talk about is two case studies really where information technology became a actually powerful tool in our investigations. The motion-picture show here is of Paula Artol-Isbrand, who is our objects conservator, and every bit the photograph suggests, she has a very swell involvement in Greek attic pottery. Well, she had known about a long standing debate most the product of Greek attic pottery, and it launched our own investigations that ultimately led to a presentation at the 2010 MRS fall meeting, and the title of that you run into here.

Thankfully, we've had the opportunity to expand on this research since 2010. Originally it was based on works from the Worcester Art Museum, just because of this inquiry, the Harvard Art Museums had fabricated accessible to united states about 18 other Greek vase shards or vases to stack up against our findings of this original inquiry.   At present, some of you lot probably could give this talk a lot meliorate than I can, but Greek attic pottery just a general overview, represents a period from 600 B.C.E to 330 B.C.Eastward, and it is by and large divided into two major areas; the black figure period and the red figure flow. Both of these works are in the Worcester Art Museum's drove, and we were particularly interested in looking at some features on the surface of the scarlet effigy vases so the Stamnos that you see on the correct, from the Tyszkiewicz painter, which had recently been conserved and asked for loan by the Getty became really, the centerpiece of this original research.

Then the product of this red figure ware and the black effigy ware really does correspond a mile stone in the history of ceramic production. It wasn't until 1970's or 1980's when a scholar really rediscovered this technique of how these things were made, and it'south really a series of different steps in the firing process under three dissimilar conditions. The outset status is an oxidation condition, and the decorative paintwork that is applied to this surface, I should say from the beginning, has more of a silica content than the residual of the vessel itself. And then in the oxidation stage, both the vessel and the surface decoration turn cherry, and so the firing weather are changed to a reduction condition and both of those surfaces plow black. But at that indicate, the temperature reached such a loftier signal that the silica in the glaze cloth becomes vitrified and is no longer really reacting with oxygen. And so and so information technology goes nether another condition of re-oxidation and the vessel turns dorsum to red once more and thus we get what we typically know as the red figure vessels. Then between the cerise effigy and the black figure vessels the technique I just described tin can be used for both of them, and the surface ornament itself, although varied and certainly beautiful in and so many unlike ways, the materials and the techniques that they used were really limited in number.

Ane technique in particular that we were interested in investigating is how did they achieve what'southward called the relief lines? The relief lines are those thin black lines in the garments and to describe the collar and the features of the face; the eyes, the nose, and eyebrows, those are called relief lines. It has been a long standing argue nigh how were those are achieved. What method is used to attain them? Scholars differed on what tools were used. So we wanted to go back and reopen the debate and run into if nosotros could add any information to what was known based on an investigation into the morphology of the lines.

The 2 techniques that we used, we figured were pretty complimentary. I already told you we were up and running with RTI within our lab, but nosotros also had admission via some bully colleagues over at WPI to the use of a light amplification by stimulated emission of radiation scanner confocal microscope. So, you're getting pretty familiar with all the pros and cons of RTI today. Laser scanning confocal microscopy, I think, although more than of a quantitative technique, whereas RTI is more of an paradigm-based technique. Light amplification by stimulated emission of radiation scanning, one of the big limitations of this project is just the gear up. You lot can see we were limited to merely shards. We are not going to put vessels on that stage and there is not really any opportunity with that particular instrument that we had admission to, to alter the musical instrument to accommodate for larger objects. And then working with shards was actually a pretty user-friendly apply of the confocal microscope. Whereas RTI allowed usa to wait at whole vessels.

So we continued with that and you've seen some live RTI'south today. These are all the same captures. The ane on the correct is a still capture, where it's really specular enhanced, it's actually a map of the surface normals and these images were so rich and informative, we were picking upwardly on things right away. And again, it'due south the way it facilitated comparing, easy comparison, you lot capture these things, and and then you had them on file, you could wait at them, go back and along, no need to get to the objects, and it was all correct at that place on the computer screen. You can from the surface normal image that the specular enhancement really improved our view of the surface and even with this lousy image, I call back you can see that already the incised lines are jumping out, y'all know those initial lines that were made to exercise the sketch of what the image was going to be, and so you also see the relief lines live up to their name. At that place is a three dimensional property to them.

So, what were some of the techniques proposed? Well, it was all over the board, from reeds to brushes to single haired or very few haired brushes, and even syringes where it was more of an extrusion technique. And this paradigm on the right of a bladder and some sort of delivery nozzle was taken from i of the major scholarly publications on how were the relief lines produced.

So, the other component of our enquiry, other than looking at things with RTI and laser scanning confocal microscopy, was to do mock ups for ourselves, investigate the  research, can nosotros reproduce what were are seeing, what we have a amend standing of through RTI? Can we reproduce it correct in the lab with our ain instruments or tools?   One of the things that RTI was showing correct from the beginning was that the relief lines were starting to split up out pretty consistently as ii distinct types of lines. There was a ridged line, so either a rounded topography to the line, or there was a furrowed line and some of the straight lines, the straight diagonal lines that you come across, those are the furrowed lines. If you look closely yous'll run across a little trough that runs down the middle of that line. Whereas the lines on the serpent head and around the middle or the curved lines to describe the ends of the garment,  those are the ridged or domed lines. So, we're thinking there'south got to exist a inkling in the fact that there is these 2 dissimilar profiles that we're seeing.

And then again, ridged line versus furrowed lines and went back to our RTI's and did further investigations. The little dots hither, that'southward a separate word I'k non going to get into right at present, but I want to call your attention to the loops at the top and the mode the specular enhancement with these RTI images actually brought out the physical properties that characterize these types of lines. How the way the ridge itself folded over around the tight curve at the loop.   Well we launched into a serial of different mockups. Here's i of our setups. The image on the left shows our extrusion musical instrument is basically a tube but for the nozzle we had used the shaft of a feather and using basically like a Gesso mixture in this case, tried to start producing the types of lines that we were seeing on the surface of the Greek vases. The image on the correct, those are two different stitched images from our confocal work where we are looking for our mock-ups, and non finding out annihilation cracking, but I but wanted to point out that information technology's pretty irregular and once more and again, no matter how hard we tried, at the starting time of the line in that location would be a heavy eolith right in the outset and information technology was almost impossible to eliminate that feature.

Then brushes didn't work, you couldn't become the turnover backdrop of that and then we got into these single hair brushes that had been proposed past a Greek vase scholar, Zadeli decades before. Hither these are all different brushes that Paula made upwardly. They included horse hair, homo hair, cat hair, pig bristles, and she really put information technology through the paces and hither is a charged brush. Here she is laying the brush downwardly in a manner proposed past Zadeli. He talked nigh laying the hair down and just lifting it upwards. And so, it'due south laid down and and then lifted up, and sure enough nosotros were getting that ridged characteristic, over and over once again with that technique. But we couldn't get that furrowed line using that aforementioned technique. Here's a small-scale bristle that we used to produce the loops and an analysis of those loops with confocal images really provided some pretty compelling evidence that the features produced with what is a mod reproduction on the left compared well with what we say in aboriginal loops on the right.

And so, what well-nigh that furrowed line? Well, we proposed that at that place is actually a distinction between techniques, the laid line and a pulled line. A pulled line is when y'all put in the single hairs down or double hairs, and pulling it across that surface, you achieve a trough profile. Hither'south two dissimilar confocal elevation maps and once again the testify for the similarities in the profiles are really compelling.

I'thou going to skip through these parts, more than metrology stuff. One of the other parts of the investigation was to look at the contour line. The contour line is that large thick line which you wouldn't see without RTI, but right along here is a ridge that get-go inscribed or cut out a larger shape. So nosotros wanted to know what came first, the relief lines of the figure, or these contour lines? And so RTI was pretty smashing at assuasive us to zoom into these features and pick-up properties that had to do with sequence. You see these relief lines extended into the groundwork and and then yous see this contour line overlapping and again and once more we saw that. Plenty so that nosotros felt that at that place was a pretty standard chronology used here. Very gratifying to go downward the Mass. pike and go to the Boston MFA and encounter a shard that has been the study from a lot of Greek vase experts, called the kylix fragment and there you lot meet a painter using who knows what kind of tool to decorate the surface, you know scribes, brushes, everything has been proposed but with RTI information technology was actually prissy to run across that the ridge there, betwixt the instrument held in the hand and the vessel, really pretty much describes that of the Linierhaar single haired castor.

So, this is going to be lightning speed but if y'all'll let me. This is an ongoing treatment at the Worcester Fine art Museum and it's on loan to us from the Purple Museum of Fine Arts in Antwerp. You'll run into right away that there is something odd virtually the portrait. It's said to be by early Van Dyke and it is pretty much agreed past all scholars that it is, but you'll see some pentiment around the neckband and around the sleeves which merited our investigations using infrared reflectography. Yous commencement to see even more of the pentiment, the fact that the man originally had one of his millstone collars that extended all the way effectually and existence a slave to manner, he brought the artist back when the styles changed and inverse the collar completely. So in ten-ray, it really jumps out. The two vertical bands are strips of canvas that are on the console joints, but you see that millstone collar and you can also see plenty of changes around the sleeves. But neither of those techniques brought our attention to something that was noticed in the lab by somebody who was less than v feet tall, standing in front of this painting on a sunny day, and noticed a little feature in the surface of this painting. We thought and we looked at it and yeah, there is something there. There might be an inscription underneath in that location that was covered over at the time of the changes to the portrait. And then we went back to the x-ray and right into that detail surface area which was in the summit left, and there was nil at that place on x-ray. Nosotros went into IR, at that place was nothing there in IR. Nosotros even did a multi-spectral approach with false color IR, UV induced physical florescence, fake colour UV, none of this was showing upwards, but of course topography and having RTI in the lab, we were hungry to wait at this with RTI. Hither again, the particular in visible light and then in RTI, you lot can see, this might be an human action of faith on your function, but you can encounter some features in here that advise an inscription.

Meanwhile this is being carried out past Matt Cushman, and I suggested to Matt, let'southward go back, let's look at our RTI, we tin can never see the whole inscription in view all at one viewpoint. But, because it's interactive, let's motility around the lighting and you can, with confidence, outline those areas you feel are definitely features. So we went ahead with that and this is the overlay that he came upward with. This represents multiple views or multiple captures taken from the RTI and then compiled equally overlays later. So information technology was great that we could go dorsum to the museum, the lending establishment, and say, you know, your painting that you've often wondered what year it was painted, nosotros now take evidence to tell you that information technology was painted in exactly 1619.

Only a terminal affair is that nosotros did map scanning with XRF, elemental map scanning, nothing in lead, naught in mercury, nothing in copper, but this is all subsurface analysis. I wanted to exercise a full map of that area. It was pretty great to come to fe. This is the surface area, but focused on one of the letters which is shaped as a J. You'll see that aforementioned letter comes up. Not only in iron, merely in manganese, which suggested it was washed with a iron oxide in umber pigment. So, information technology was pretty bully that we could go that far in RTI, having facilitated it.   Then the conclusion, maybe information technology's coming out like a mantra today. RTI can in some cases, provide insight where other established methods, such as X-rays and infrared reflectography cannot and therefore is a actually valuable method in the larger field of technical art history.

Thank you very much.

Speaker Bio

Philip Klausmeyer earned art history and studio art degrees from the University of Massachusetts, Amherst, and an MS from the Winterthur/Academy of Delaware Program in Art Conservation, specializing in paintings. In add-on to fifteen years at the Worcester Art Museum, his conservation piece of work includes fourth dimension at the Strauss Centre for Conservation, Harvard Academy and the Museum of American Fine art at the Pennsylvania University of Fine Arts, Philadelphia. In 2009, he received a PhD from Clark University where he focused on applications of immunological methods in the assay of fine art materials. He is currently Worcester's conservation scientist and associate paintings conservator.

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Source: https://ncptt.nps.gov/blog/applications-of-reflectance-transformation-imaging-rti-in-a-fine-arts-museum-examination-documentation-and-beyond/

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