The paper is the major printing material of book printing. The book printing color is depend on the ink and paper. Thus, the paper characteristic will affect the book printing quality.

1. The whiteness of book printing paper

The paper's whiteness refers to how reflective the paper is to visible light. We often express as a percentage. If the paper nearly reflects all color light of a range of visible light wavelengths. Its color is close to pure white, and the whiteness is very high. The high whiteness paper can reflect all the remaining parts of color light after the ink selective absorption. So that to achieve printing book's color reproduce and make the ink color full play. Since the pulp raw material, the paper with not high whiteness, gray, and some paper is yellowish. If add the fluorescent whitening agent, the paper often has a bit of bluish. The paper with lower whiteness, strong absorption, it will make the book printing color look dim. And it will reduce the brightness and saturation. If the paper is color cast, it can't reflect the various wavelengths of light uniform. It as well as bring the color cast for book printing.

Because the color lightness and the paper's whiteness will affect the screen layering. From the view of color vision, the paper is more white; the ink is more deep. The clearness is more better and the layers are more highlight. Otherwise, the paper is more gray, the printing color is dim, the contrast and picture will be poor. Such as children's book printing, to make the book color more bright, and screen layering are more rich. We often with high whiteness coated paper to print children's book.

2. The smooth, gloss, absorbency of book printing paper

The paper's smooth refers to the degree of paper surface is flat, uniform and smooth.

The paper's glossy refers to the degree of paper's surface mirror reflection. We can express as a percentage. High glossy, and the mirror reflections are dominant, slow reflections are less. 

The paper's absorbency refers to the degree of paper's absorption of the binder and its solvent in the ink.

Coated paper with coating on the surface. After super calendaring, the surface is very smooth. When we print the ink on the paper, capillary absorption in the coating layer is uniform. Even the volume of ink is less, it also can ensure a high rate of transfer. When change the ink volume, the ink transfer rate is still keep stable. And then can form a uniform, dry ink film quickly. So that the printed books surface with high glossy, bright color, rich layers. 

The paper has high smoothness, strong mirror reflection and good gloss. When the light passes through the ink layer and irradiates the paper. Most of the light will re-penetrate the ink layer in mirror reflection and enter the observer's eyes. Only this part of the light can reflect the ink's color rendering properties. So when printing the book with rich pictures or colors inside. Such as art book printing, photo book printing, board book printing, etc. Often use coated paper to print such of books. So that can make the books achieve the effect of high glossy, bright color and rich layers.

Offset paper and other un-coating paper. Their surface with characteristic of large pores, uneven, poor smoothness, low gloss. When the ink volume is less, the paper can't full touching with the ink. The transfer rate is lower, it will happen the dot loss. When the ink volume is high, the transfer rate is high, ink absorption is too strong, ink dry too slow. The printed book surface with bad glossy, and reduce the color lightness and saturation. It can't meet the fine print needs. If the ink absorbs too strong, it will cause the connecting material in ink is most absorbed by paper. And can't better protect the pigment particles. And as a result, the ink marks are not strong. Resulting in chalking, through-printing, shriveled marks, and dull colors. 

To make up for the above defects, we have to increase the amount of ink unilaterally. Although it can increase the ink color, but it will also bring about a serious increase in dots and deformation. Resulting in a large loss of layers, especially in the dark tones, and a series of quality defects.

To sum up, the paper characteristic is good or not, it will finally affect the color quality of book printing. In the actual production, we need to select the printing paper type based on the printing quality needs and printing budget. In the proofing, we'd better use the same paper as mass production printing, to keep consistency.