The quality of printing paper is mainly judged from the following aspects

(1) Appearance quality. Appearance quality refers to the defects that can be observed by the naked eye such as dust, hole, needle eye, transparent point, wrinkle, ruffle, striation, net print, hair cloth mark, spot, slurry, cloud flower, crack, and inconsistent color.

(2) basic physical characters. Basic physical characters include paper weight, thickness, compactness, smoothness, hardness, softness, compressibility, absorptivity, and other common characters.

(3) Mechanical properties. The mechanical properties are also called mechanical properties or strength properties, which are divided into two types: static strength and dynamic strength. 

The static strength of the paper is the maximum force that the paper can bear under the condition of slow stress, and is also called the final strength. It includes the following quality indicators: tensile strength, durability, tear, tolerance, stiffness, etc. 

The dynamic strength of the paper means the strength of the paper which can be subjected to the instantaneous impact, which reflects the dynamic state of the instantaneous diffusion after the paper is stressed. The dynamic strength mainly includes the following indexes: the puncture strength, the ring pressure strength, the compression strength and so on, which is the most important quality index of the packaging paper and the paper board.

(4) Optical properties. Optical performance refers to whiteness (brightness), luster, gloss, transparency, opacity, etc. For printed paper, the optical properties of paper is very important, it directly affects the quality of printed matter.

(5) Chemical properties. Chemical properties of paper include chemical composition, hygroscopicity, ash, sizing, acidity and durability.