Color build up is considered one of the colorant qualitative characteristics, and it is proportional to the amount of saturated colorant, so that colorant materials with the same structure and color index number which produced by different companies, also don’t have the same build up. The most common method of determining color build up the empirical and visual experiments, but all of the visual assessments depend on the observer judgement and test conditions, therefore repeatability of the test results may be decreased. This study aims to present a new method for evaluating build up of colorant materials and determining the appropriate criteria to describe amount of build up using principal component analysis method for spectral data. Primarly, the standard depth of 1/1 for each dyestuff was determined separately, due to operate this evaluation and with respect to color build up definition. Samples were dyed with different proportions of 1/1 standard depth and their spectral reflectance values were measured. Afterward the scalable region of K/S function for dyes samples at different concentrations was determined. The main direction of data and their eigenvalues were determined using principel components analysis of the K/S functio and reflecting data separately and percent of cumulative variance has been calculated to express the amount of color build up. As well as K/S function variation versus concentration were also evaluated due to further analysis of suggested method results. Furthermore utilize of color data and their color difference values were also examined, concerning standard depth for each dyes and have been compared with results obtained by using principal component analysis. Finally, validation of obtained criteria operation via the stated method was also examined by comparing the results of visual tests have been done. The results show that the proposed criteria using this method can quantitatively determin the amount of color build up through spectral data. Keywords: Color build up, Principal component analysis, 1/1 standard depth, K/S function
