The purpose of this diploma thesis was to prepare a screen printing ink with a natural colourant obtained from the rhizome of the Japanese knotweed and to check its applicability for printing on paper and textiles. Printing inks were prepared in six different dye concentrations. The following materials were used for printing: 4 papers made from the stem of a Japanese knotweed of different grammage, 2 papers meant for general use (one from primary cellulose and one from secondary cellulose), cotton and polyester fabric. All printed samples were colourimetrically evaluated. The prints of the papers were checked for rubbing resistance and tested for colour fastness to light. The textile prints were, in addition to light and rubbing resistance, also checked for resistance to wet ironing and household washing. All prints with ready-made printing ink are coloured yellow on all printing materials. After being exposed to artificial light the prints darkened and turned to orange-brown colour. The darkening was greater with the prints who had higher concentrations of the dye. The durability of the prints on fabrics for washing and other wet treatments is very poor, which limits the use of printing ink for printing on fabrics. All paper prints are very resistant to dry rubbing; cotton and polyester fabric prints also have excellent resistance to dry rubbing, but their wet rubbing resistance is quite poor. The colour fastness of the prints on cotton and polyester fabric to wet-hot ironing is good only with the lowest ink concentration in the printing ink.