Using 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, since it enhances the detectability of minor spectral features. In this project different madder types were collected and applied for dyeing woolen yarns used in Persian carpet in the same pre-mordanting and dyeing process with different amount of 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 used in dyeing of Persian woolen carpets to dye concentration. It was discovered 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.