Spectroscopy Helps Us to Chronicle Our Past
With the advent of new technologies, great strides have been made in the scientific study, identification, preservation, and restoration of historical documents. And by historical documents, I’m not simply talking about written documents like the Dead Sea Scrolls or a deed registry from 19th Century Tombstone, Arizona. Before modern visual media and now, the Internet, the representations available to chronicle the human condition were often of the visual kind: paintings.
To better understand the origin and authenticity of these historical “documents” that bear witness to the human saga, it is essential to understand their origins and composition. In the past, field experts have relied on knowledge of period history as well as an artist’s style, brushstroke nuance, and available pigments. While a grasp of this knowledge remains ever so important, over the last decade, new spectroscopic tools have become available to historians, curators, and collectors of fine art.
Results from shortwave infrared reflectance imaging spectroscopy of Picasso's The Tragedy (1903).
Spectroscopy, or the measurement of spectra produced when an object interacts or emits light, has been around for over a century. By evaluating the specific wavelengths of light reflected or emitted by an object, you get a very good understanding of its elemental components. It’s used both terrestrially and cosmically to figure out whether there’s rust on the Golden Gate Bridge or the surface of Mars. And because it can assist in determining the makeup of most anything exposed to light, it is an exceptional tool to identify the type of canvas, pigments, and methods used by long departed artists.
If you take a quick look online, any respectable art museum involved in the provenance and conservation of fine art has a long list of esoteric equipment at their disposal. Among these devices are sophisticated spectrometers that operate in the ultraviolet, visible, and infrared parts of the spectrum – all crucial for the investigation and identification of artworks. These devices and methods are tried and true, but even over the last decade, new and capable hyperspectral imaging (HSI) equipment and techniques have greatly enhanced the science. HSI takes spectroscopy to the next level and allows you to quickly map your spectrometric results as the target appears. This spatial organization is comfortable, organizing spectral data in the form of the target. Not only can you see the layers and use of pigments in van Gogh’s The Starry Night, but the data persists in a familiar arrangement, offering an opportunity for the scientist to further interpret an artist’s methods and intent.
There are several HSI solutions now on the market offering this capability for both in-situ and lab analysis. None is perfect and often sacrifices capability for cost, size, or speed. Remember that camera resolution and measurement modality remain important factors for the earnest investigator, so beware the ultra-compact solution as they are often lacking in spectral resolution and flexibility. And software matters – off-the-shelf solutions are manageable, but proper software for efficient discovery and diagnosis is the fine line between success and failure.
Artists pursue their craft in an effort to pique our senses with light and color. Little did they know how much more information they were sharing both on and below the painting’s surface – information beyond what can be seen or touched. Ever-improving HSI technology is the key to revealing this oft overlooked essential, unbiased data, unveiling histories hiding in plain sight.
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