Different batches of color printing plants have different densities in the same location.

Dalian color printing plant includes box board paper, cement bag paper, high strength corrugated paper and brown board. Kraft paper is made of softwood kraft pulp with tough texture, strong strength and yellowish-brown paper surface. It can be divided into single-sided, double-sided, striped and non-striped varieties in appearance. The quality requirements are slightly different. Kraft paper is mainly used for the inner packaging of small paper bags, document bags and industrial products, textiles and daily department stores. Kraft paper is divided into U, A and B3 grades. In fact, it refers to the comprehensive effect of various appearance characteristics of printed matter.

From the perspective of reproduction technology, the quality of printing should be based on the standard of "faithful reproduction of original manuscripts". Whether in the traditional printing process or in the digital process, faithful reproduction of original manuscripts should be achieved for printed matter. There are four control factors for printed matter: color, level, clarity and consistency.

Color is the basis of product quality, which directly determines the quality of products. Color control or management has always been a hot topic and key technology in the research and analysis of printing professionals. Hierarchy, or step, refers to the change of color gradation that can be recognized by an image. It is the basis of accurate color reproduction. Cleaning degree refers to the clarity of image details, including three aspects: the clarity of image details, the clarity of image contour edges and the clarity of image details.

Consistency is uniformity, which includes two aspects. On the one hand, it refers to the consistency of ink volume in different parts of the same batch of printed matter, i.e. different ink areas. Generally, it is measured by the consistency of vertical and horizontal field density of printed matter. It reflects the stability of different parts of printed matter printed at the same time. On the other hand, it refers to the consistency of the density of different batches of printed matter in the same position, which reflects the stability of the printing press.