Printing ink in normal storage process composed of crust and in the use of emerging in the process of the crust usually give printing factory and the captain brought a lot of trouble, for example lower cost is increased and the print quality of the products. If can be in prepress and use of the process can effectively control the crust representation, which for the printing factory has a great significance. 

The so-called crust is due to oxidation at room temperature, infiltration, evaporation, transpiration and dry, printing and packaging in storing and printing process with the outer layer and the air touch, transpiration of the oxidation of vegetable oil or organic solvent, resulting in the polymerization etc. effect and form a gel. When the ink concentration increases to a certain value, the surface will be covered by a layer of molecules, when even with the addition of solvent or fat to reduce the concentration of oil. When the knot skin image is grim, the first will be a great influence on the stability of the printing costs. According to the calculation, the light by 1%, or nearly 4%. This tangible consumption has increased the economic burden of packaging and printing companies. Second, the impact on the quality of printing products can not be ignored. When printing process after the crust, cushioned will under the effect of rolling to various aspects of the transmission distribution, normal ink has a great influence on together when a cushioned adhesion on the version of the rollers on the time will make printing graphics shows dense sudden; when a cushioned transmission to the printing plate and rubber cloth on time, will enable printing presents annular scars; when a cushioned adhesion to water and time, so that water is not normal, showing a dirty appearance; a cushioned there may be directly attached to the paper surface. 

From the above we can see that the prevention and treatment of skin appearance is necessary. So how does the knot skin image appear? 

We talked above, the skin surface is a kind of convergence between the surface of the oxide film. The mechanism of the conjunctiva is the same as the dry mechanism, which is affected by the factors such as temperature, humidity, oxygen in the air, the content of dry agent and so on. In a brief way, the appearance of the crust is actually a kind of phenomenon that we don't expect to see in the oxidation of the conjunctiva. 

There are many factors that can cause the skin to skin, but it is mainly due to the high content of dry oil in printing ink, because of the temperature reason, because of the long-term touch with the air. Here are some of us to do some analysis. 

1 ink in the dry oil content is too high usually in the process of manufacturing or printing process is likely to show such a mistake. Increase the dry agent is bound to contact the print conditions and environmental temperature appropriate increase, otherwise it will not be expected to dry in the dry. 

2 because of the formation of temperature 

The crust formed by temperature is mainly formed by temperature. When the temperature is too high, the activity of unsaturated molecules is enhanced, especially the appearance of the air is somewhat easier to be oxidized under the effect of oxygen. Here the temperature is high, there are several aspects of the following: 

A) ambient temperature is too high, based on our experience, usually in the summer skin appearance significantly more than in winter, if there is no air conditioning in the workshop will be more significant. Reasonable control the temperature of the working environment is necessary, generally can control the workshop of temperature control in 20 DEG C is an ideal temperature, which can ensure the good flow and transfer, and the crust in a relatively low degree. 

B) when the machine is on the surface of the skin. When the roller between the touch pressure big time, temperature and increasing the contrast significantly, then it is easy to show appearance crust on the ink fountain and ink roller. 

The precise adjustment and control of the pressure rollers in the printing process, on the prevention of crust have very important significance. 

C) from leaking out of the dryer air drying surface, or hot air to form a fountain in the. 

D) and other abnormal heating up of the machine. 

3 because of long-term contact with air to form 

Ink in the composition of the material and the air in the oxygen in the oxidation reduction reaction, exposed in the air is too long, of course, will be oxidized, showing the appearance of skin. Usually this kind of knot skin mainly has the following several: 

A) not for the time being, exposed to the air in place, a long time will appear on the surface of a thick oxide film. We in printing factory will have such experience, when from the ink or ink barrel out ink containing the time, to avoid the appearance keep a flat state, reason to do so is to minimize air and touch area, so even if posterior conjunctival waste ink will a lot less. Then it is to cover the remaining use of protective film, blocking the touch with the air, so that it can effectively prevent the appearance of the skin. 

B) printing machine long-term shutdown, no clean ink, ink fountain roller and formed in the crust. In work must pay attention to when a long-term shutdown time, will ink clean, when the shutdown time is not very long time can be selected in ink spraying anti skinning agent.