Excessive emulsification of ink and various preventive measures

1.

If the ink emulsification is just right, it shows that the ink is in a relatively balanced state, creating good printing conditions for offset printing, and the graphic ink can realize the transfer of the ink, so as to obtain the printing effect of smooth and neat dots, clear images, rich layers, bright and saturated colors , and ensure the accuracy of the overprint and promote the drying of the print, while ensuring that the blank parts of the non-printing area are clean and tidy

Therefore, whether to correctly grasp and control the emulsification of ink is the key to ensure the balance of ink and water and stable printing quality

Excessive emulsification of the ink means that there are too many tiny droplets dispersed in the ink, exceeding a certain proportion, and the properties of the ink will change immediately, such as the color becomes lighter, the color saturation decreases, the viscosity decreases, and the adhesion is weakened, etc.

For example: the gray balance is broken, the color is not restored, the color of the printed product is dark, and the level is unclear; the ink transferability deteriorates, the ink color is suddenly large and small, and the ink color difference between the front and rear of the product is large; The drying performance of the imprint is greatly slowed down, which is easy to cause the backside to be dirty, etc.

2.

There are many factors that cause excessive emulsification of ink, mainly including paper, fountain solution, ink, diluent and desiccant, etc.

1.

Since paper, such as some offset paper, coated paper, and whiteboard paper, contains more or less surface active substances in the sizing, coating or other fillers on its surface, they have a certain water-solubility.

The greater the moisture content of the layout, the more fillers will be dissolved, and the more serious the emulsification will be

Preventive measures: ① Use better quality paper to fundamentally prevent excessive emulsification of ink caused by paper; ② Wash rubber and printing plates frequently, and remove fallen paper powder and paper wool in time; ③ Add a small amount of additives to the ink, And reduce the moisture of the layout and the pressure of the water roller, so as to reduce the paper powder and lint

2.
Fountain factor

The dispersion of the fountain solution is one of the conditions that cause the emulsification of the ink.
The water film on the surface of the printing plate, under the action of the mechanical force, forms tiny droplets that disperse and penetrate into the ink, causing the emulsification of the ink, so the amount of water in the fountain solution is If it is too large, the water film of the printing plate is too thick, and the water spread along the ink roller increases.
After the mutual extrusion of the roller and the ink roller, the ink emulsification is accelerated and over-emulsified
.
The larger the amount of water, the thicker the water film, the smaller the PH value, and the more serious the over-emulsification
.

Preventive measures: ① Control the water volume of the fountain solution, and reduce the amount of ink and water under the condition that the printing plate is not dirty and the print meets the quality requirements of level, density, color, etc.
; ② Control the ratio of the fountain solution, PH The value should not be too small, it is best to use alcohol fountain solution as much as possible
.

3.
Ink factor

The viscosity of ink is the main factor to produce emulsification, regardless of the viscosity, it can produce different degrees of emulsification
.
The viscosity of the ink is large, the molecular cohesion is large, the water resistance is strong, and the emulsification value is small; on the contrary, if the ink viscosity is small, the fluidity is strong, the cohesion between the molecules is small, and the water resistance is poor, it is easy to emulsify
.
In general, ink viscosity is inversely proportional to emulsification, and fluidity is proportional to emulsification
.

The difference in the water repellency of the pigment itself will also cause the change of the emulsification value of the ink.
For example, the water resistance of black ink and red ink is better than that of green lotus and peacock blue ink, and the emulsification value is also smaller
.

Preventive measures: ①Select inks with good water resistance; ②For inks that are easy to emulsify, increase the viscosity of the inks, and ③replace with new inks
.

4.
Diluent and desiccant factors

The commonly used diluents mainly include lightening agent, white oil, white ink, vigor oil, etc.
Among them, the lightening agent is an amphoteric oxide with strong hygroscopicity and a large emulsification value.
The emulsification value of white oil is also large, which is extremely It is easy to cause the emulsification of the ink.
If these diluents are added to the ink, the emulsification of the ink must be accelerated; driers such as white drying oil and red drying oil have a large emulsification value.
Adding an appropriate amount of drier can speed up the drying of the ink.
However, if it is added in excess, it will reduce the drying speed of the ink and worsen the emulsification of the ink
.

Preventive measures: Add diluent or desiccant according to the specific situation, do not add it blindly, try to control it within a certain amount, generally around 2%-3%, not more than 5%
.

5.
Over-emulsification caused by other factors

Other factors, such as workshop temperature, humidity, vehicle speed, and the pressure of water rollers and ink rollers, will also have a certain impact on ink emulsification
.

For example: the higher the workshop temperature, the higher the surface temperature of the roller and the ink roller, the thinner the ink, and the greater the fluidity, the lower the viscosity, and the weaker the water resistance.
The over-emulsification of the ink has a strong catalytic effect.
The higher the workshop temperature, the easier the ink is to be emulsified
.

Preventive measures: ①Install air conditioners in the workshop as much as possible, control the temperature of the workshop between 20℃-26℃, and control the humidity between 53%-65%; ②Pay attention to adjusting the pressure of the water roller and ink roller to make it within a suitable range Inside, ensure smooth water and ink delivery; ③ When the machine is idling, the water supply and ink supply should be turned off to avoid the large amount of water and the large ink speeding up the emulsification of the ink
.

There are many factors that affect the emulsification of ink.
In many cases, the cause of excessive emulsification of ink is often a combination of several factors, such as: small image and text area, low ink consumption, and long-term contact between ink and water.
Emulsification, if the water resistance of the ink is poor and the amount of water is too large, the ink is more likely to be over-emulsified
.

Therefore, for the problem of ink emulsification, we should analyze and eliminate them one by one from various aspects.
We must establish the idea of ​​​​prevention before it happens, and focus on prevention.
Process operations, such as: do a good job of "three leveling" and "three diligence", find and solve problems in time, and pay attention to accumulating experience, grasp the appropriate ink emulsification as much as possible, control the balance of ink and water, and print out clear dots, distinct layers, and color.
Vivid high-quality print
.