Application of Derivative Spectrophotometry to Determine the Relation Between Color Intensity and Dye Concentration of Madder

The Derivative Spectrophotometry usually improves resolution bands, eliminates the influence of background and provides more defined fingerprints than original spectra, hence enhancing the detectability of minor spectral features. In this work, different madder types were collected and applied for dyeing woolen yarns used in Persian carpet in conventional pre-mordanting and dyeing process with different amounts of the dye. The second derivative of the Kubelka-Munk function of dyed samples has been calculated and implemented for eliciting a function that relates the color intensity of madder to dye concentration used in dyeing of Persian woolen carpets. It was found that for all selected madders, an exponential function could be appropriately adjusted to control this relation. Thus the concentration of madder used in an unknown woolen yarn could be approximately determined with the fitted function.