Zoom in on a digital image, and it'll turn into a grid of pixels. Zoom in on a tapestry, and you'll discover a grid of interlocking threads, with each segment contributing a color and texture to the whole. From a distance, what looks like bright copper in the 16th century tapestry The Triumph of Bacchus is actually a combination of crimson silk, and gold threads. Micrographs of the tapestry, taken by conservators at The Getty, bring every minute detail to light: the undyed wool warps stretching horizontally, providing support to the overall structure, the crimson silk spiraling vertically, and alongside it, these incredibly thin strips of gilt silver wrapped around yellow silk. Zoom back out, and you'll discover—and better appreciate—the full composition:
Triumph of Bacchus, design overseen by Raphael, ca. 1518-19; design and cartoon by Giovanni da Udine in collaboration with other artists from the workshop of Raphael. Brussels, workshop of Frans Geubels, ca 1560. Le Mobilier National, Paris. Image © Le Mobilier National
Close study of woven threads can sometimes reveal even more than compositional data. At the Asian Art Museum in San Francisco, conservator Shiho Sasaki worked with Professor Chi-Sun Park, of the Jung-Jae Conservation Center in Seoul, to analyze a Buddhist painting from 18th century Korea. Even with a microscope of relatively low magnification (which Prof. Park brought with her from Korea, where it is commonly used by dermatologists or beauty technicians), they were able to see that the artist painted right onto the cloth, without applying a ground layer first, and gathered clues about the work's cultural context: "Confucianism was promoted by the government, so the imperial workshops would have produced paintings on tightly woven silk, with proper ground layers, that were Confucian in theme. Because they lacked government support, Buddhist themes were often represented using less expensive materials and techniques. Under a microscope, you can really see how roughly our painting was made in comparison to a high quality work made for the court," explains Sasaki.
"The threads were not carefully made or woven. With a microscope, you can see how they are inconsistent in their thickness—some have multiple strands of fiber, some only one or two. Some threads are twisted, while some are flat," adds the conservator. And while it's more than likely that this painting was made on cotton rather than silk, Sasaki notes that a more powerful microscope would be needed for "100% accurate fiber identification."
At 400x magnification or more, in polarized light, things become a lot clearer—and more colorful. Conservators can compare what they see under the microscope to known references, such as those found in the Fiber Reference Image Library, and identify whether they're dealing with silk, cotton, or hemp, for example. Natural fibers are usually easier to identify: If you spot nodes along the length of the fiber, it might be flax or jute, while cotton will look like a twisted ribbon. Manmade synthetic fibers, on the other hand, often look similar, so special attention must be paid to their few distinguishing characteristics in order to make an accurate assessment. At the Met's Costume Institute, fiber identification is a regular part of the job for conservators like Glenn Petersen, whose micrographs can be seen below. A magnified view of silk tulle from a wedding dress even shows how starch—which is added to stiffen fabric—is present in the triangle-shaped interstices of the netting.
You can follow The Getty's #artunderthemicroscope series on their Tumblr, learn more about the Asian Art Museum's survey of Korean paintings here, and go behind-the-scenes at the Costume Institute here.