Pigments with Personality

This month I have been pulling old batches of silver nanoparticles from their warm resting place in a storage cabinet and putting them to the test. I wanted to see if the particles still function after aging for a long period of time and how the performance of these old particles compare to the most recent batches that are nestled in a cold refrigerator. The series of tests that I put each batch of particles through range in difficulty from amplifying the signal of a pigment with a reputation of yielding intense spectra to amplifying the signal of a more stubborn pigment within a paint chip. Getting a strong signal from an organic pigment that is surrounded by layers of varnish, oil, or other components of paints, is more difficult than getting a signal from pigment alone. Thus, the optimal batch of silver nanoparticles would easily amplify both a lone pigment and a pigment as a component of paint. While there was not a clear winner across the board of the tests, I was pleased that every batch was still functional in some capacity.

With this comfort that the particles seemed to be less erratic than I originally thought, I decided to turn my attention from optimizing the silver nanoparticles to optimizing a protocol to pretreat art samples to extract pigments of interest. I focus on identifying red pigments that are known to fade over time. Briefly mentioned above, some pigments’ signals are more difficult to amplify than others. Carmine is one example of a pigment that yields a nice spectrum consistently. On the other hand, madder lake is more challenging in that I cannot always count on getting a nice spectrum. I intend to continue efforts that the lab has already begun in trying to make madder lake easier to find, and I look forward to looking at precious samples from real works of art soon.

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