Printing with Natural Dye Extract from Japanese Knotweed Leaves

Abstract Invasive alien plants are detrimentally displacing native plant species and pose a challenge in terms of how their overgrowth can be utilized effectively. In our study, the leaves of one of the world’s worst invasive species, Japanese knotweed, were used to produce a green natural dye. This dye was screen-printed onto various substrates, including cotton and polyester fabrics, commercial cellulose papers, and innovative papers made from the stems of Japanese knotweed. The printed substrates were evaluated using color measurements and fastness properties. The aim of the study was also to investigate the influence of additives in the printing inks, such as sodium carbonate, citric acid, copper and aluminum sulfates, on the color and fastness properties of the prints. The colors of the prints obtained varied, ranging from primarily yellowish-green to brownish-yellow with the addition of citric acid, orange-brown with sodium carbonate, orange-yellow with aluminum sulfate, and brown with copper sulfate. The prints had excellent fastness to dry rubbing and moderate fastness to light. The prints of lower and medium dye concentrations on fabrics had very good fastness to wet rubbing and wet ironing, and on cotton even good fastness to washing. The additives in the printing inks, such as sodium carbonate and metal sulfates, reduced the abrasion resistance of the prints on paper and the wet fastness of the prints on fabrics, but only the metal sulfates had a positive effect on the light fastness of the prints.