Analyzing Color Samples
A number of scientific tools are used to identify and analyze pigments and dyes. Polarized light microscopy (PLM) is one of them. Using PLM, we can examine pigment particles on a microscopic level, taking a small paint sample that’s been carefully removed from an artifact and viewing it through transmitted, polarized light under a microscope.
Other techniques — like Fourier transform infrared (FTIR) spectroscopy — identify color by measuring the responses of an unknown color sample to different forms of radiation, including x-rays and infrared radiation. These measurements are recorded as a chart — called a spectrum — that can be compared to the spectra of known samples. The molecular structures and even the isotopic signatures of pigment samples can be measured and compared to known examples in order to identify the type and, in some cases, the geographic sources of pigments and dyes used on an artifact.