fluorescence microscopy
Fluorescence microscopy takes advantage of the ability of certain materials to absorb light at one wavelength and give it up or “fluoresce” the light at a longer wavelength to help characterize the constituent components of a material through routine microscopic examination. Fluorescent dyes, which carry reactive groups on them, have also been used in this regard to “tag” or make fluorescent certain common paint and varnish binding materials. Among these reactive dyes are Rhodamine B (which helps highlight oil-containing materials in paint and varnish samples); Alexafluor488 (which fluoresces proteins-containing layers); and TTC (triphenyltetrazolium chloride, which “tags” carbohydrates, such as gums). (Preservation Science, 2019)