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Anyone interested in the finite and microscopic analysis of color can e-mail me and I'll refer them to John, he loves to ponder and is quite verbose
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The type of microscopic tests I was referring to do not even look at the color of the particles but the molecular structure and size of particles to identify specific pigments. These are also sometimes combined with chemical spectrum analysis. So, if say, a lead white was mixed with a chrome oxide, they would look for those pigments and chemical compounds and try to determine the amounts of each. They also would try and determine the binder or type of oil used, and if there was a varnish applied what type. This is a very scientific process that has more to do with molecular chemistry then color theory. You could even be color blind and do these tests.
Now this is different than a paint chip analysis, where they try to look at the different layers to find the hue and shade that a mix of pigments produced. For the same color hue and shade and value can be made from different pigments. It is important that conservators know the exact pigment used and the exact type of oil or other mediums used to bind those pigments. Also they need only a very small sample (small like the size of a pin point or the point of a dental tool) The microscopes they use are like an electron microscope that can see the molecular structure of a particle.
But even with all these advanced tools, they still have to make educated guesses as to the painting process. These tests have been used to try to determine the authenticity of paintings, and even with all of this, experts still can't always agree. As you might imagine, a painting that has been around for a few hundred years would have plenty of exposure to all kinds of contaminants that could disrupt the findings or cause enough doubt to make them inconclusive.