The color printing process of washed kraft paper involves multiple aspects, including ink selection, printing techniques, paper processing, etc., to ensure the desired printing effect.

Firstly, due to the inherent color of kraft paper, in order to make the printed colors more vivid, it is best to use brightly colored ink and use more eye-catching colors, which can achieve better color effects. In addition, adding a little white to the ink first can achieve a light color effect, which is beneficial for color reproduction.

In terms of printing techniques, due to the strong permeability of kraft paper, flexographic printing is generally used, and offset printing machines are not suitable for printing because the latter is prone to the phenomenon of paper shedding during printing. Meanwhile, improving the surface smoothness of kraft paper can also help reduce the generation of dust and avoid harm.

In terms of paper processing, kraft paper needs to be hung, dried, and humidified before printing to remove torn paper and uneven surface paper, clean impurities, and maintain the same temperature and humidity as the offset printing workshop to prevent the phenomenon of paper curling up and scraping down due to uneven moisture content. In addition, choosing the appropriate printing machine is also very important. For thicker kraft paper, using a split offset press or a full open offset press will produce better printing results.

To solve the problems of color darkening and insufficient whiteness, white background ink can be applied below the colored part to cover the natural color of the kraft paper, and the ink can be stacked repeatedly to achieve satisfactory thickness and whiteness. However, it should be noted that paper shrinkage and deformation may occur during the process of printing with stacked ink, resulting in inaccurate color matching, which needs to be resolved through other methods.