This week, a group of us attended a lab session regarding the restoration and conservation of art with Dr. Sonia Mugnani. The day started with complimentary bags, and progressed with a tour of the geology laboratory, which contained a variety of scientific instruments, including a mass spectrometer and XRF machines, both of which have been discussed in class. The most interesting part though was learning the versatility of these machines, in that geologists on a regular basis used them. Though in retrospect it seems rather obvious that geologists would utilize tools to analyze the structure of rocks and such, it was fascinating to see how applicable it truly was, not only in geology but art as well. For example, Dr. Mugnani handed out two XRF plots for two different pigments; red and orange. It was our task to use Bragg’s equation to determine the chemical composition of these pigments. Bragg’s equation uses the angle at which an x-ray is diffracted through an object, and then uses the values for slit length to determine what the compound was.
Bragg’s Equation:
2 d sinø = λ, where:
d = diffraction gradient
ø = angle of beam
λ = wavelength
The outcome of our pigment, which was a red color, was mercury sulfide or vermillion....ironic, huh?
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We did powder x-ray diffraction, not XRF.
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