Lithography is based on the principle of oil-water immiscibility. The graphic part of the plate can be hydrophilic and hydrophobic, and the blank part can be hydrophilic and hydrophobic by water first. In addition, for print book china, offset printing is characterized by indirect printing, using the way of dot color reproduction. It is very 
important for the normal transfer of imprint, the depth of ink, the accuracy of register, the dryness and stickiness of printed matter. Therefore, whether the ink balance can be controlled correctly is the key to ensure the stability of printing quality. As a skilled printer, he should not only understand the relationship between ink and water balance, but also master the techniques and essentials of ink balance.
1. The relationship between ink and water balance
Water ink balance means that under a certain printing speed and pressure, the supply of fountain solution is adjusted so that the volume proportion of the fountain solution contained in the emulsified ink is controlled at 15% - 26%, and the water in oil (w / O) emulsion ink with slight degree is formed, which can compete with the ink on the printing plate with the minimum liquid supply.
Ink balance is the most important fountain solution and ink control. The fountain solution is composed of water and surfactant. The fountain solution can fully moisten the plate, has the cleaning ability and stable pH value to ensure that the plate is not dirty.
1) Function of fountain solution of print book china
� In the blank part of the plate to form a uniform water film to prevent the ink on the text to the blank part of the infiltration, to prevent dirty version.
� The electrolyte in the fountain solution reacts with the exposed metal substrate due to wear to form a new hydrophilic layer continuously to maintain the hydrophobicity of the blank part of the plate.
� Controls the temperature of the ink in the layout. As the speed of the new printing press is faster and faster, too fast printing speed will increase the temperature of the ink in the high-speed transmission, increase the fluidity of the ink, and cause the dot to increase. Therefore, the high-speed machine puts forward new requirements for fountain solution, that is, when the fountain solution contacts with the ink roller through the layout, it can reduce the temperature of the ink roller and ink.
� Do not enlarge or shrink the text. The fountain solution must have the function of stabilizing the relative position of the graphic part and the blank part of the printing plate, so as to ensure that the picture and text are neither enlarged nor reduced in the whole printing process.
Ink is generally composed of pigments, fillers, binders and auxiliary additives. The rheological and optical properties of ink should be fully considered when selecting ink.
The rheological property of ink is the main basis to judge whether the ink has good printing performance. The rheological property of ink mainly depends on the binder of ink, of course, it can also be adjusted by auxiliary additives. The evaluation of ink rheological properties can be reflected by the main indexes of ink rheological properties, namely, viscosity, thixotropy, yield, viscoelasticity and fluidity. In actual production, only by mastering these performance indexes can we be familiar with the printing properties of various types of inks, so as to achieve the purpose of selecting the ink that meets the printing requirements.
Printing ink and water must exist at the same time and keep balance. The purpose is not only to maintain the maximum ink load in the graphic printing area, make the ink bright, saturated, clear and smooth, but also keep the printing area highly clean and tidy. Therefore, it is necessary to pay attention to the relationship between water supply and ink supply in production.
In process of print book china, the ink depth of printed matter is not only related to the amount of ink in the ink holder, but also directly affected by the water supply and the balance of ink and water on the page.
When the moisture content of the layout increases, the imprinted ink gradually lightens. On the contrary, with the decrease of water supply, the water content of the layout will be reduced, and the imprinted ink color will be relatively deeper than the original. Therefore, increase or decrease the amount of ink supply and layout water supply will change the color of imprinted ink. In the printing process, it should be adjusted according to the actual situation. We should not simply rely on reducing water supply to improve ink color, because the water content is too small, losing the balance of ink and water, which is easy to make the blank part dirty.
However, it is necessary to prevent the practice of big ink. When the water content is too much and the ink color becomes lighter, we must not ignore the actual situation and mistakenly think that the amount of ink supplied is small. Instead of reducing the water supply, we should increase the ink quantity frequently. In this way, the amount of water supply for ink supply is increased, resulting in a vicious circle, and finally all kinds of disadvantages of large amount of water and ink appear, making printing unable to be carried out normally.
In practical production of print book china, experienced printing workers usually control the water supply in a small range on the premise that the printing plate is not dirty, and make the water supply and ink supply in a relatively stable state, so as to ensure the consistency of ink color before and after printing and the stability of printing operation. It is advocated to adopt the method of small water and thick ink. The water small here refers to the minimum amount of water on the premise that the blank part of the page is not dirty. The so-called ink thickness is also based on the small amount of water. Large amount of water causes excessive emulsification of ink, and the ink layer is impossible to be thick.
