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How can spectrographic analysis identify the elements in a tiny paint sample?

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Hear about William Henry Ireland's fake manuscripts of William Shakespeare including a letter written to his wife — Forgery A look at a letter supposedly written by William Shakespeare to his wife, Anne Hathaway; it was, in fact, faked by William-Henry Ireland.

Spectrographic analysis is a highly sensitive chemical analysis technique used to identify the elemental composition of materials, such as a tiny paint sample, without requiring the destruction of large amounts of evidence.12

When a minute sample—sometimes as small as the head of a pin—is burned, the atoms within it are vaporized and excited to higher energy levels. As these excited atoms return to their lower, stable energy states, they emit light at characteristic frequencies unique to each element.12

This emitted light is then dispersed into an ordered sequence, or spectrum, using a prism or diffraction grating. By capturing a photographic record of this spectrum, researchers can analyze the specific wavelengths present to identify the elements in the sample and determine their relative percentages. This objective data allows experts to compare the pigments found in a suspected forgery against those known to be used by an artist during a specific historical period, helping to reveal inconsistencies such as the presence of modern synthetic chemicals in works purported to be ancient.21