The Goldenrod (Solidago), an invasive alien plant which is also found in Slovenia, represents an environmental problem. Because it contains the dyes from the flavonoids group, its aqueous extract may be used for the textile dyeing. The dye has poor affinity for the cellulose fibres and this limitation can be improved with the mordanting or cationic pre-treatment of fibres. Within the diploma thesis, the influence of pre-treatment process on dyeability of cotton with natural dye obtained from the goldenrod inflorescence was studied. Dyeing was carried out on samples without cationic pre-treatment or mordanting (reference samples), with mordanting prior to dyeing, mordanting during dyeing and with cationic pre-treatment. The mordant used was potassium aluminium sulphate dodecahydrate (Kal(SO4)2 × 12 H2O) and the cationic agent was DENIMCOL FIX-OS. Dyeing was carried out in two repetitions at three different concentrations of the goldenrod aqueous extract, i.e. without dilution and by dilution with distilled water at the volume ratios 1:2 and 1:3. The spectrophotometric evaluation was performed on the dyed samples before and after repeated washings. The colour fastness to rubbing was evaluated visually according to the grey scale. The colour fastness to artificial light was evaluated according to the blue scale as well as spectrophotometrically on the dyed samples before and after illumination. The results show that the cationisation process of cotton fabric significantly increased the sorption of the goldenrod dye from the dye bath in comparison to the samples which were mordanted before or during dyeing as well as the untreated ones. The cationic pre-treated samples also had the highest colour fastness to washing, rubbing and light.
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