A technique of separating colored substances and analyzing their chemical structure by chromotographic adsorption. Differences in the rate of movement along a liquid or solid column are noted and used for the identification of organic substances. Archaeologically this can be useful for identifying sources, as for amber. There are several methods of chromatography, but particularly used in archaeology are paper and gas. In the former, a solution of the substance to be examined is placed at the end of a piece of filter paper; the end is then dipped into a solvent which moves the constituents of the sample along the paper by capillary action. Different substances reach different points on the filter paper and, by comparison with reference substances, can be identified. Gas chromatography is done by introducing the mixture into a column of material. The mixture is carried through by gases and measurements of the gas coming through over time are made by a gas detector. The use of gas chromatography in the study of amber has shown that different sources produce different chromatograms.