Natural dyes for textile dyeing;A comparison of methods to assess the quality of Canadian golden rod plant material

摘要

The introduction of natural dyes into modern textile dyehouses requires the classification of products of standardised quality with regard to colour depth and shade of the dyeings.Canadian golden rod was chosen as a representative example to test the methods that are available to assess the quality of different crops of plant material which had been collected over a period of five years.Aqueous solutions containing the extracted flavonoid dyes were characterised by means of direct photometry,measurement of absorbance after addition of FeCl2,analysis of total phenolics(TPH)in the extract and dyeings on wool yarn.TPH calculated as gallic acid varied from 62 g/kg to 97 g/kg of plant material;only one sample exceeded this range with a value for TPH of 142 g/kg.Correlation among TPH,photometry in the presence of FeCl2 and lightness of the dyeings can be used to characterise samples.However,correlation between the photometric results and colour depth of dyeings is not sufficient to permit characterisation of the plant material with regard to the final dyeing.At present,a combination of laboratory dyeings and CIELab coordinates was found to be suitable to establish an experimental basis for standardisation of plant material.