Cotinus coggygria extract has been used as a dye for silk, wool and leather in Eurasia, including Azerbaijan, since ancient times. In order to be an artisanal staining of these products it is used raw – crude extract of fisetin obtained from the wood of smoke trees. To obtain a uniform color in certain product batches a dyeing bath with a certain density of fisetin is prepared. Our experiments show that in the spectrum of the crude extract fisetin in 95% ethanol, there are two characteristic UV/VIS bands. The band of the first group located, with a maximum of about 314 nm, arising from the B ring, the second – with a maximum around 412 nm arising from the A ring. This gives us reason to say that in order to establish the amount of fisetin in the dye solution, one of the earliest methods of ultraviolet and visible spectroscopy can be successfully used.