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X-Ray Visions

Fused mosaic plaque; Ptolemaic dynasty to Roman period; 100 BCE–100 CE; Egypt; F1909.506

Fused mosaic plaque; Ptolemaic dynasty to Roman period; 100 BCE–100 CE; Egypt; F1909.506

Ellen M. Nigro is an intern in the Department of Conservation and Scientific Research at Freer|Sackler.

In 1909, Charles Lang Freer made his third trip to Egypt and bought a collection of nearly 1,400 ancient glass beads, vessels, and mosaic fragments in Cairo. The objects are mainly XVIII dynasty, Ptolemaic, and Roman period Egyptian pieces, but include some later Islamic fragments. Although the collection varies a bit in geographic origin and time period, all the pieces are colorful examples of fine craftsmanship, from intricate millefiori inlays to cast amulets. Freer shipped the collection straight to the Smithsonian in 1910; since then, some of it has been exhibited, but the vast majority was left unstudied. However, the current installation The Nile and Ancient Egypt features selected glass vessels from this collection. Concurrently, a scientific study of the glass collection using x-ray fluorescence (XRF) is helping researchers at Freer|Sackler understand better the elemental composition of the objects.

This image was taken with the XRF spectrometer camera of the glass object at top.  The instrument allows us to focus the x-ray beam using a laser and video camera.

This image was taken with the XRF spectrometer camera of the glass object at top.

XRF is a non-destructive, scientific, analytical method that is capable of detecting inorganic elements with certain atomic weights. The colorants in glass are mainly transition metals (those found in the middle of the periodic table such as manganese, iron, cobalt, and copper); therefore, XRF is a good way to learn about what materials the ancient glassmakers used to make the vibrant colors in this collection. (It is not able to determine chemical structures or detect organic compounds, chemicals mainly composed of carbon, hydrogen, and oxygen.) XRF uses an x-ray beam generated inside the instrument to displace inner shell electrons in the elements of the analyzed material. Higher energy electrons then cascade down to lower energy levels and release energy in the form of fluorescence. As this fluorescence is released, the instrument detects the signals and creates a line graph on a computer program, where the analyst can see the results. The x-axis represents the energy of each signal in kiloelectronvolts (keV), while the y-axis represents the intensity in number of pulses. Since each element produces a characteristic set of peaks at specific energies, the scientists can determine what elements are present in the material.

The graph gathered from the blue area in the fused mosaic. The cobalt peak is highlighted because it is likely the main colorant.

The graph gathered from the blue area in the fused mosaic. The cobalt peak is highlighted because
it is likely the main colorant.

Knowing the colorant can also provide clues about the time and culture in which a piece originated. For example, if a white glass produces strong antimony and calcium peaks, it could be colored with calcium antimonate, a common white colorant in XVIII dynasty Egypt. But if a white glass sample produces prominent tin peaks, the results suggest the colorant could be tin oxide, a material used starting around the fifth century CE. At the end of this XRF survey, the scientists at Freer|Sackler will have a much better understanding of the elemental composition of these glass objects. Although the results from XRF alone only give a small glimpse into the history of these objects, this study can help guide further scientific and art historical research.

Learn more about Conservation and Scientific Research at Freer|Sackler and check out another blog post on x-ray art.

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Zooming In: Geometric Patterns in Islamic Paintings

Magnification reveals geometric patterns in a detail of a painting of a stained glass window from
the Haft Awrang by Jami. F1946.12.147

Amanda Malkin is the Hagop Kevorkian Fund Fellow Paper Conservator at the Freer|Sackler. This is the first in a series of blog posts that explores geometric patterns in Islamic paintings.

While viewing Islamic paintings under the microscope, I developed a great interest in the tiny geometric patterns I observed throughout the folios and set out to learn more about them. Prior to my research, I had not studied the history of Islamic culture and was completely unaware of the Islamic Golden Age, an innovative, experimental, and forward-thinking time in early Islam, which spanned from the ninth to the thirteenth century. During this time, there was a boom in the study of mathematics, physics, geometry, optics, vision, astrology, and many related disciplines. This efflorescence of discovery resulted in the development of new concepts and an expansion of ideas first posited in ancient Greece and Rome.

I began to examine how artisans and manuscript illustrators interacted with mathematicians, and if the techniques used to create geometric patterns in manuscript paintings were a result of those connections. It’s clear from several scholarly articles and publications written on this productive era in Islamic history that artisans and mathematicians were in contact with one another. One treatise, written by the Persian mathematician and astronomer Abul Wafa al-Buzjani (940–998) during the Golden Age, has been used by many scholars to provide evidence of this exposure of artists to mathematicians and those studying geometry. The title of his work, On those Parts of Geometry Needed by Craftsmen, alludes to this interaction. He describes many instances in which he had observed craftsmen practicing geometric constructions and ornamental patterns with mathematicians.

It is also clear from the scholarly literature on this subject that not all artisans were invited to join in these gatherings. The math and scientific communities held those artisans of scientific equipment in much higher regard than artists of other trades, who were considered a lower class. This bias likely excluded many artisans from working directly with mathematicians. The collective ingenuity of the time, however, leads one to assume that they must have discovered many other avenues to acquire and piece together the basic concepts of geometric design and pattern construction.

It’s amazing what an image under a microscope can reveal. In the next post in the series, I’ll take a closer look at the tools and techniques used to create miniature geometric designs.

Learn more about Conservation and Scientific Research and the Islamic art collections at the Freer|Sackler.

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Spring Cleaning in Paper Conservation

Emily Jacobson, paper conservsator at Freer|Sackler cleans a painting using a vacuum pick-up tool.

F|S paper conservator Emily Jacobson cleans a painting using a vacuum pick-up tool.

Emily Jacobson is paper conservator at Freer|Sackler.

Everyone knows that spring is the time to clean house: throw open the windows and doors, let in the fresh air, and shake off the cobwebs of winter. Well, we may gently remove the cobwebs here at the Freer|Sackler, but we don’t throw open the doors and windows. There are a number of reasons why it’s critical to control the environment in a museum, most importantly to help preserve the collections and slow down deterioration. It is particularly important for works on paper, as they include some of the most vulnerable materials used to create art. Works on paper need to be protected from dust and particulate matter that might settle on the surface. The temperature can’t become too hot, as that could accelerate reactions leading to the discoloration of paper or desiccation of paint binders. The relative humidity needs to remain moderate and stable; if it gets too high, mold can grow on the surface of the paper or paint.

Detail of fuzzy, brown-colored mold on a pastel drawing which obscures the black and blue media beneath.

Detail of fuzzy, brown-colored mold on a pastel drawing, obscuring the black and blue media beneath it.

While we have excellent temperature and relative humidity controls in the museums, many works in our collection arrived here after being stored in poor environments. One of the problems we occasionally encounter is old, dry mold on the surface of a painting. While the mold, which looks like powdery fuzz, may not be actively damaging the surface, it could be reactivated by high humidity. In many cases, the mold also obscures details and colors in an artwork. So, we remove the mold to prevent the possibility of problems down the road and to improve the art’s appearance.

Mold-before-and-after

Mold on a painting (left) and after cleaning (right).

Mold is an irritant and can even be toxic, so we don’t just brush it off into the air. We remove it using a small device called a vacuum pick-up tool, which incorporates an aquarium pump. The pump has been modified: instead of pushing air into a tank of water, it pulls air through a needle-nosed tool at the end of some tubing. The suction is extremely gentle, so it can be used on delicate paint with cracks and insecure media. Using a soft brush, we move the mold toward the tool’s tip, where it is drawn into the tubing.

In conservation, spring cleaning doesn’t just happen in the spring. The care of objects and attention to detail goes on year-round. Stay tuned to Bento for more inside looks at our work.

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X-Ray Art: The Conservator Will See You Now

An x-ray of Bodhisattva Avalokitesvara (Guanyin) in the guise of a Buddha reveals three wood support screws; China; F1957.25

An x-ray of Bodhisattva Avalokitesvara (Guanyin) in the guise of a Buddha reveals three wood support screws. F1957.25

Eve Rosekind, an art history major at Johns Hopkins University, was a summer intern in the Department of Conservation and Scientific Research at Freer|Sackler.

For the past sixty-two years, the Department of Conservation and Scientific Research has used x-radiography in its study and treatment of Freer|Sackler objects. The department houses approximately 4,170 x-rays of paintings, sculptures, ceramics, and prints that have been examined by the museums’ conservators and curators.

To preserve these images, the Smithsonian’s Office of the Chief Information Officer funded a project to digitize all of the department’s x-ray films. Digitization also makes the images more accessible and easier to use in studying the collection. My summer efforts focused on cataloguing and organizing the x-ray films and their corresponding digital images.

In x-radiography, film is placed beneath a work of art, which is exposed to x-rays in order to create an image on the film. A visual record of the condition of the piece at the time it was taken, an x-ray can reveal how an object was constructed, as well as any subsequent treatments or changes.

X-ray: Dagger-axe, China, bronze with iron ore, F1934.11

An x-ray of a dagger-axe from China showing signs of “channeling.” F1934.11

A number of our x-rays are on a cellulose acetate film-base and are now deteriorating. The deterioration is characterized by three main symptoms:

1. The film becomes brittle and small parts begin to break off.
2. Known as “channeling,” the different layers of the x-ray shrink at different rates, causing air pockets in the film. In the image above, the lines on the film are examples of channels on the surface of the x-ray.
3. The “vinegar syndrome.” The deterioration of acetate film is due to chemical decomposition that produces acids—in this case, acetic acid—that escape from the film in the form of a gas, causing a vinegar-like smell.

One example of how an x-ray can show the construction of an object is the image of a Chinese ivory standing Buddha (pictured at top and digitized so that it could be included in this blog post!). The x-ray is a close-up of the Buddha’s head and upper torso. In the middle of the head, the large wooden screw that attaches the head to the rest of the body can be seen along with two other wooden screws in the shoulder. These wooden screws are part of the original construction of the ivory statue and are used to hold the multiple pieces together.

X-ray of  Long Lagoon by James McNeill Whistler, F1887.10

The x-ray of “Long Lagoon” by James McNeill Whistler reveals the watermark. F1887.10

The x-ray pictured above is of a Whistler etching on paper. In this image, the paper’s watermark is visible. A watermark is made by impressing a thin wire design into the paper when it is being constructed. The wire thins the paper, and when light passes through the design is visible. This specific mark, containing a fleur-de-lis beneath a crown, is known as the Strasburg Lily, which was used on paper throughout Europe from the seventeenth to the nineteenth century. The letters LVG, seen below the lily, most likely refer to Lubbertus van Gerrevinck, a paper manufacturer in Holland and possibly in England. Revealing the watermark can help determine who made the paper, as well as when and where it was made.

We can learn a lot from a work of art, and some of what we learn lies beneath the surface. Each x-ray image is unique and shows the object in a new light. Now that the films are digitized, it will be easier to share these images with researchers and the public. This summer, my project gave me an incredible perspective on an aspect of the museums’ collections rarely accessible to others.

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Squeezing is Believing

 

Detail of cuneiform squeeze. Ernst Herzfeld papers, Freer Gallery of Art and Arthur M. Sackler Gallery Archives.

Larry DeVore is a retired lawyer who became a docent at Freer|Sackler twenty years ago. Shortly thereafter, he began volunteering in the Department of Conservation and Scientific Research. For the last fourteen years he has been working with our paper conservators, first Martha Smith and now Emily Jacobson. He has been involved in many different projects, including the repair of a collection of “squeezes.”  

A squeeze is a paper cast of an inscription or picture that has been incised on an outdoor monument or building. In this way the inscription, which could become eroded or destroyed over time and cannot be moved to another location, can be preserved. Large sheets of wet paper are pounded into the recesses of the inscribed surface and once the wet paper dries it is peeled off the surface.

The F|S Archives was given more than three hundred squeezes by Ernst Herzfeld, an archaeologist who worked in a number of Middle Eastern countries, including Iran, during the 1920s and 1930s. Over time many of the squeezes, of cuneiform inscriptions from sites such as Persepolis, had suffered damages. There were tears in a number of different places, the cuneiform was frequently compressed, and often sections of the cast were missing. In addition, repairs made previously used poor-quality materials, such as scotch tape or brown paper tape, which had to be removed before new repairs could be made. Tears and holes were mended using Japanese paper and a good-quality adhesive and the cuneiforms that had been crushed or damaged were restored to their original height where possible.

If you want to see for yourself what a squeeze looks like, come to the Feast Your Eyes: A Taste for Luxury in Ancient Iran exhibition that is currently on display at Freer|Sackler. If you look closely, you might even see where some of the repairs were made.

Learn more about the Squeeze Imaging Project at the museum.

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