43rd Annual Meeting-Book and Paper Session, May 15, 2015, "16-17th Century Italian Chiaroscuro Woodcuts: Instrumental Analysis, Degradation and Conservation" by Linda Stiber Morenus, Charlotte Eng, Naoko Takahatake, and Diana Rambaldi

The presenter, Linda Stiber Morenus, began her discussion of these complex prints with a description of the printing process. Chiaroscuro woodcuts were intended to emulate chiaroscuro drawings, which were comprised of black chalk shadows and white chalk highlights on colored paper. Color oil-based printing inks were first used to print 14th-century textiles, being used on paper by the mid 15th-century. The chiaroscuro woodblock prints required two to five separate woodblocks, inked with different shades lighter and darker than the midtone colored paper.
In order to better characterize the media, Morenus collaborated with art historian Takahata, and conservation scientists Eng and Rimbaldi from the Los Angeles County Museum of Art (LACMA). In addition to prints at LACMA, the team studied prints from the British Museum and Library of Congress. Out of over 2000 surveyed woodcuts, 72 were studied in depth, with X-ray Fluorescence (XRF), Fiber Optic Reflectance Spectroscopy (FORS), and Raman spectroscopy. Inorganic compounds were indicated by XRF analysis. FORS was especially helpful for detection of indigo. Raman spectroscopy provided additional information about organic colorants.
Renaissance artists’ manuals, such as Cennino Cennini’s Libro dell’Arte guided the research by providing information on the most likely colorants for printing inks. Inorganic pigments included lamp black, lead white, ochres, vermillion, verdigris, and orpiment. Organic pigments included indigo and a variety of lake pigments.
After providing background information, the presenter began to focus on deterioration and conservation of the chiaroscuro prints. The prints from the Niccolo Vicentino workshop had a high lead content. The inks typically had a low vehicle-to-pigment ratio, tending to turn gray around the edges, due to the presence of lead sulphide. Verdigris corrosion was also a common problem, as found on “Christ Healing the Paralytic Man” by Giuseppe Niccolo Vicentino, as well as 13 other prints from the same workshop. Typical copper-induced paper degradation included yellow-brown halos around inked areas and cracks in the paper.
Fading and discoloration were major problems for the organic colorants, such as indigo and the yellow lakes. Morenus compared copies of Ugo da Carpi’s “Sybil Reading a Book” in the British Museum and the Library of Congress, finding clear evidence that the indigo in the British copy had faded. The British Museum had confirmed the presence of indigo through Raman spectroscopy. At least 8 of the prints were found through XRF to have high levels of calcium in the same areas where indigo had been identified, suggesting the presence of chalk-based lakes. Organic greens had shifted to blue or brown where organic yellows had faded or become discolored.
The presenter concluded with suggestions and caveats for conservation treatment. First, she advised conservators to exercise caution in aqueous treatment, in order the preserve the topography of the prints. The woodblock creates a relief impression in the paper, and the layering of the inks adds another level of texture that might be altered by humidification, flattening, washing, or lining treatments. The low binder content also makes the inks more vulnerable to saponification and loss during alkaline water washing. Morenus warned that the hydrogen peroxide color reversion treatment for darkened lead white would be particularly risky, because the white lead sulphate end product has a lower refractive index than basic lead carbonate original pigment. This means that treated lead white becomes more translucent, and the lower “hiding power” shifts the tonal balance of the print to appear darker overall.
For exhibit recommendations, Morenus suggested that we should always expect to find fugitive organic colorants in chiaroscuro prints, so exhibit rotations should be planned accordingly. Maximum exhibit conditions should be 5 foot-candles (50 lux) of visible light for 12 weeks of exposure, no more often than every three years. She also indicated that overmatting should be avoided to reduce the risk of differential discoloration.
During the Question and Answer period, Morenus clarified the color order used in printing. Some prints were inked from dark to light, but most were printed with the lightest color first.
I thoroughly enjoyed learning about these beautiful prints, but I think that the discussion of the lead white conversion treatment-induced refractive index shift was the most important “take-away” from the presentation.

Contemporary Print Identification Workshop

Print workshop looking at Intaglio-Type prints brought by Keith Howard
Print workshop looking at Intaglio-Type prints brought by Keith Howard

I was very happy to be part of the group of paper conservators gathered in Washington, DC from October 16th- 19th, 2013 for an in-depth study of print identification.
On day 1 and the first part of day 2, the workshop hosts Scott Homolka and Stephanie Lussier, led us through the different categories of print processes, starting with traditional, familiar techniques; then looking at examples of variations and recent developments that might be harder to identify unless you know what you are looking for. We also had several guest lecturers on day 2. Shelley Langdale, Associate Curator of Prints and Drawings at the Philadelphia Museum of Art, gave a lecture on the history of American printmaking studios in the 20th century. Keith Howard, Head of Printmaking and Research at the Rochester Institute of Technology, and Bernice Cross, master printmaker and owner of White Cross Press, brought in examples of contemporary prints created by them and their students in a variety of techniques for us to examine closely. Keith Howard invented the field of non-toxic printmaking with a process he named Intaglio-Type. He has published several books about his techniques and kindly gave each participant a copy of his most recent one, entitled The Contemporary Printmaker: Intaglio-Type & Acrylic Resist Etching, which is considered an essential manual by many people in the field of printmaking today. Lastly, the three printmakers behind the printmaking website Printeresting; Amze Emmons, R.L. Tillman and Jason Urban, gave a talk about the world of printmaking today.
Scott Homolka explains Richard Serra's process of applying paintstick through silkscreenScott Homolka explains Richard Serra’s process of applying paintstick through silkscreen
Day 3 was spent at the National Gallery of Art. Lucky for us, the government shutdown ended just in time to spend our final day at our planned venue. Our first exercise in the morning was to identify the processes behind some prints in their collection. Some of the prints were particularly tricky, while others were deceptively easy. Then we went to the galleries for a tour of the exhibit Yes, No, Maybe: Artists Working at Crown Point Press given first by the curators Judith Brodie, head of modern prints and drawings, and Adam Greenhalgh, Andrew W. Mellon Postdoctoral Curatorial Fellow; then by one of Crown Point Press’ Master Printers, Emily York. This show features both working proofs and final prints in order to show the process that goes into making a print. Not all of the projects resulted in a print that the artist considered exhibitable, but all showed the creative and technical process behind the creation of prints and in some cases expanded what was possible in printmaking by pushing at the boundaries of the techniques.
Then it was back to the lab to look at Marian Dirda’s collection of printmaking papers from the late 20th and early 21st century. She is a great resource for information about fine art paper mills, and the papers that particular artists or printmaking studios prefer. In fact, I should emphasize that all of the lecturers of this workshop are very accessible and happy to share their knowledge with the conservation community. I recommend reaching out if you have questions about contemporary prints.
Rosemary Fallon practices a non-toxic version of the 'acid bite' techniqueRosemary Fallon practices a non-toxic version of the ‘spit bite’ technique
On day 4, we travelled to Pyramid Atlantic in Silver Spring, MD, where we got to try out Intaglio-Type printmaking for ourselves. Keith Howard and Bernice Cross led us through plate preparation, exposure, development, and printing. After 4 hours, we each had 1-2 prints to keep as references. Day 4 was absolutely my favorite part of the entire workshop. I learned that many studios offer summer weeklong intensive courses in printmaking. I hope to take one someday.
Thanks again to everyone who worked behind the scenes to make this workshop possible despite the government shutdown.
Bernice Cross demonstrates 4-color printing from plexiglass plates
Bernice Cross demonstrates 4-color printing from plexiglass plates



Contemporary Print ID Workshop Begins Despite Government Shutdown

We were all looking forward to spending three days at the National Gallery and one day at Pyramid Atlantic looking at prints, but just as the start of the workshop approached, the government shutdown began. With the National Gallery closed indefinitely, the workshop organizers had to scramble to make alternate arrangements.
As one of the participants, I am happy to report that they were successful. The Corcoran Gallery of Art was able to provide space for us, and we had a great first day.  We reviewed familiar print techniques and terminology, and learned some new ones (for me, anyway), such as CNC, or computer numerical control- using a computer to achieve detail and precision that would be difficult or impossible by hand; soap ground, or white ground- a technique using a mixture of soap flakes, linseed oil, and water to create painterly white areas; and water bite- using an acid/water mixture on a tilted plate to create subtle gradations in depth.
We have begun day two and will be going more in-depth on contemporary print processes and hear from some guest lecturers, including: Marian Dirda from the National Gallery; Shelley Langdale, of the Philadelphia Museum of Art; and Amze Emmons, R.L. Tillman and Jason Urban from the website Printeresting.
Thanks to Stephanie Lussier, Scott Homolka, Abigail Choudry, and everyone from AIC and the Corcoran that made this workshop possible despite the shutdown.