It has fallen on textile conservators to keep historic textiles preserved, and a surprising amount of science aids them in this quest.
By Fernanda Ferreira
PhD Candidate in Virology
Harvard Medical School
Introduction
In one of the lower-level exhibition rooms of the Museum of Fine Arts (MFA) in Boston is a large red and blue mantle from Peru made of camelid wool. Stylized faces embroidered in yellow, blue, green, and red smile back at you from behind the thick glass, while blue and red bands alternate across the mantle, giving it a decidedly modern feel that belies its true age: this mantle was weaved approximately 2,000 years ago by the Paracas, an Andean culture that preceded the Incas.
If you have spent any time walking past ancient textiles in museums, you know that the bright colors of the Paracas mantle at the MFA are unusual; in many ancient textiles, the colors have become muted, going from vivid blues and reds to dusty azures and maroons. The Paracas mantles were discovered in burial sites along the arid coast of Peru where, away from sunlight and the UV rays that break down chemical bonds in chromophores (the color bodies of dyes), their rich colors were preserved for millennia. Since their excavation in the 20th century, however, these mantles have become vulnerable to light, heat, moisture, and microbes, which hasten their degradation. It has now fallen on textile conservators to keep these mantles and other historic textiles preserved, and a surprising amount of science aids them in this quest.
All Come from Dust, All Return to Dust
In museums, far away from the throngs of museum goers, are entire labs dedicated to the conservation of a museum’s collection. After all, every physical work of art degrades over time: dust obscures paint; celluloid in old photographs crack; metal sculptures corrode; sunlight bleaches tapestries. Conservation is the act of trying to slow this degradation so that the art can continue to be enjoyed and studied.
While degradation is inevitable for all materials, it is especially damaging to organic materials, which the majority of textiles are woven from and dyed with (Figure 1). The camelid wool of the Paracas mantle came from llamas or alpacas, and the dyes used to create the bright colors in it came from plants and insects.
To minimize degradation, conservators create stable environments that protect the textile from further degradation. These stable environments are tweaked depending on the type of textile, so before conservators can construct these environments, they must first understand what they are dealing with.
Investigating Textiles
Look at the pair of Huron-Wendat moccasins from Quebéc in the “Collecting Stories: Native American Art” exhibition at the MFA. With your untrained eye, you will notice the colorful beads and red fibers that decorate the moccasin, as well as the dark leather material that forms the shoe. A conservator will see much more: the fibrous material is animal hair that has been dyed red; the “beads” are actually porcupine quills; and the shoes are made of more than just leather, there’s also wool and silk.
Every piece that enters a museum collection goes through a condition evaluation. “In this process, we’re trying to document the materials and the technology used to create the piece,” Meredith Montague, Head of Textile Conservation at the MFA, told me last month. She added that this also helps to place the piece within a time period and culture.
There are many scientific techniques that can be used to investigate the nature of a textile, ranging from chromatography—which identifies dyes—to dipping a sample of the textile in sulfuric acid and observing how it reacts; cotton (a natural fiber) will dissolve, while polyester (a synthetic) will not.
In the Harvard Art Museums, Dr. Georgina Rayner, a conservation scientist, often uses matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, or MALDI, to investigate the protein makeup of pieces in Harvard’s collections. For example, natural fibers like wool and animal fur are mainly composed of keratin, a protein that is the principal structural component in our hair and nails. Rayner explains that keratin samples from different species have unique markers that can identify the animal that a natural fiber came from.
Sometimes, the condition of the sample dictates which techniques are used. In a 2000 study of textile artifacts recovered from Pompeii, Herculaneum, and Scafeti—three cities that were buried under ash after Vesuvius’ eruption in 79 AD—scanning electron microscopy (SEM), optical microscopy, and wide angle X-ray scattering were all used to investigate the nature of the textile fibers. These methods were chosen because most of the textiles had been burned and chemically altered by hot volcanic ash, so chemical tests were out of the picture. Furthermore, because these were precious archaeological materials, researchers had to work with tiny samples weighing less than 3.0 milligrams (~0.0001 ounces). Despite these limitations, these three techniques have allowed researchers to look at the morphological characteristics of the fibers making up the textiles (Figure 2), showing that ancient Romans used a variety of materials, from common cotton and wool, to the more exotic kapok and coir, in their textiles.
Goldilocks Textiles: The “Just Right” Environment
Once a textile’s nature and origin have been thoroughly investigated, conservators move to the next step: slowing degradation. Here again, science plays a role. “We use [science] to understand deterioration mechanisms of organic material, and we use scientific principles to help stabilize environments so that the textiles will last longer,” explains Montague.
A moist environment can lead to mold, while a dry environment can embrittle a textile, Montague notes. As such, textiles must be comfortably stored in a narrow spectrum of temperature and humidity that’s just right for that piece.
Light is another big factor in deterioration. “Sunlight we exclude altogether,” emphasizes Montague. As for artificial lighting, UV rays are removed either by using filters or specific light sources that lack them entirely. In storage, pieces are kept in the dark, but if a piece is on display in the museum, conservators will control the amount of time a textile is on exhibit to preserve it for future generations. After all, all light—even light where UV rays have been removed—can cause irreparable and cumulative damage to a textile.
Science and Art
Science is applied in all steps of textile conservation from the moment a piece enters the museum’s collection to the decision of how long it remains on display. After all, as Montague explains, science is an integral skill set for conservators: “The three legs of the stool for conservation are: hand skills, appreciation of art history, and then there’s the science.” And, while lot of the science in textile conservation, and in art conservation in general, is applied science, research is always ongoing in museum labs with the intent of finding even better conservation techniques.
So, the next time you’re at a museum, stop and really look at a textile on display. Whether it’s a Jan Moy tapestry or a brocade from Japan, many areas of science were used to understand the work before you and to make sure that both you and future generations can continue to enjoy it.
Originally published by SITNBoston (Science in the News), 12.01.2018, Harvard University, under the terms of a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International license.
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