Also on ink thickness

First, the relationship between the viscosity of ink and the thickness of the black layer "Ink" text said: "Increase in the thickness of the ink layer, the viscosity is also increased accordingly, the ink's mobility is small." Here the ink viscosity, fluidity. So, what is the viscosity of the ink?
Viscosity is a physical measure of ink performance. It is defined as a measure of the ability of the inter-particle interactions to hinder their relative motion, and viscosity is a measure of the cohesion of the ink. Viscosity units are "poise," "centimeters," or "pa.s. seconds," and "mPa.s.seconds."
Ink viscosity is usually measured with a "rotating viscometer" (Emila viscometer), a "drop bar viscometer" (Laray viscometer), and a "parallel plate viscometer." It can also be measured with bubble viscometer, capillary viscometer, falling ball viscometer, cone-plate viscometer and other instruments. It is worth noting that the amount of sample ink used when measuring the viscosity is strictly limited. Using a rotary viscometer, the ink is placed in a measuring barrel. Using a drop stick viscometer, the ink was placed inside a thick-walled tube. Using a parallel plate viscometer, the amount of ink dropped on the glass plate was 0.5 cm3. In other words, the viscosity is a unit of quantity, and it is a measure based on the unit physical quantity, not an arbitrary variable.
When the ink layer thickness changes, does the viscosity change for the same ink? No! What changes here is the total adhesion of the ink, not the viscosity. Imagine an ink that has a viscosity when we use it for one kilogram, another viscosity when we use it for 0.5 kilograms, and a new one when it takes 0.1 kilograms. The viscosity; what is the significance of that public measurement of its viscosity?
Here again relates to another physical quantity of ink - viscous. Macroscopically, "viscosity" and "stickiness" represent the same type of performance. But they are not the same thing. Viscosity is a measure of the resistance to resistance when the ink is fractured and separated. The viscosity of the ink can also be determined using special instruments. But it is not dimensioned.
Fluidity also has a well-defined definition: the ability of an ink to expand its diameter under the influence of pressure. The fluidity can be measured with a flow meter.
The ink is a non-Newtonian fluid. Its movement is much more complicated than Newtonian fluid. Viscosity is not only related to its own structural components, but also related to temperature. The fluidity is not only related to its own structural composition and temperature, but also related to the thixotropy of the ink.

Under normal circumstances, the viscosity and fluidity change in the opposite direction, that is, the greater the viscosity, the lower the fluidity, the lower the viscosity and the greater the fluidity. But they are not inversely proportional. For example, when corn flour is added to the ink, the viscosity is reduced, and the fluidity does not increase, but decreases.
Second, the relationship between ink depth and ink layer thickness "Ink" text said: "The printing of dark ink, the amount of ink can be appropriately thin. Because dark ink hiding power is relatively strong, not easy to produce the bottom of the flowers."
Ink thickness is a very important issue, but also a very sensitive issue. However, it is not related to ink color. For the continuous adjustment of the manuscript is a printed matter, in the People's Republic of China industry standard "CY/5-91 "Plain print quality requirements and inspection methods,"" has a clear provision.
Item 4.1.1 of the standard lists "Table 1 density range":
The density on the ground here represents a thick layer of ink. Because if there is no defined ink layer thickness, there is no accurate neutral gray balance and there is no correct color reproduction.
In order to achieve normalization and data management, there is a corresponding field density test area in the "GATF Color Copy Test Chart" in the United States. In the future, the development of printing to CTP requires a color environment. This environment is standardized management data.
At present, the most advanced multi-color offset printing presses are already available with pre-settings. It determines the thickness of each color ink layer, either through a plate scanner or through various interfaces to input pre-set data. The thickness of the ink layer will not be darkly adjusted for the hue of different colors.
For packaged prints that consist entirely of spot color patches, the use of thicker ink layers is allowed without having to consider the problem of neutral gray balance. However, the appropriate ink layer thickness can still be determined by the "GATF test pattern" method. However, it is not based on the difference of visual observation and color, but on the basis of physical compatibility with paper.
The coverage of the ink is not shifted by the depth of hue, but by the transparency of the ink's raw materials. The four-color offset inks currently available on the market have sufficient transparency. It must have the ability to both print and print four-color dot overlap products.
Third, the relationship between paper quality and ink thickness
"Ink" in the article said: "For printing paper rough surface, soft texture, strong ink absorption products, the hue to adjust the ink slightly, the printing ink layer can be appropriately thicker."
The first thing to emphasize is that as stated earlier in this article, the hue and density of the ink are regulated and should not be arbitrarily adjusted. If the printability of paper is related to the ink-related part, it is the following two aspects:
1. The paper's color reproduction adaptability It is mainly determined by the paper's whiteness and reflectivity, and its data can be measured in the "GATF test chart". In general, the color rendering of paper is directly proportional to the smoothness of the paper surface and inversely proportional to the ink absorption of the paper. Thus, some experts designed the concept of "paper efficiency." It can be calculated using the following formula:
PSE=100-A+PG/2
In the formula: PSE - Paper Efficiency A - Absorption PG - Paper Gloss From the experimental results, it is consistent with the ink tape printed on the paper with the ash rate, color deviation ratio, and the actual efficiency trend.
2. The surface strength of the paper is a direct manifestation of its suitability for the removal of powders during the printing process. It is related to the viscosity of the ink and also related to the printing speed. Here, I am still willing to avoid the direct layer of ink. The thickness of the ink layer is still determined by the color reproduction value of the product. What should I do if the powder off occurs? You can use the method of adding No. 6 varnish to properly reduce the viscosity of the ink. In low temperature environments, pre-inked inks can be used. As for the relationship with printing speed, there is a formula that can be calculated:
VP=3600V/2Ï€ 4.7R (sheets/hour)
Where: VP - printing speed V - critical pull speed R - impression cylinder radius under the premise of other conditions remain the same, you can calculate the print speed limit, in order to ensure that no paper off powder .
There is also some expression and quotation of professional vocabulary such as “friction coefficient”, “ink absorption” and “coloring power” in the “ink” text, and it is also not strict enough and accurate. In view of the length of space and the level of my own, I do not have to discuss this one by one.
In general, the number and quality of engineering and technical personnel in the printing industry in China are far from adequate. There is a considerable distance between the existing level of theoretical knowledge and actual needs of technical knowledge. I put forward the above personal opinions on the relevant contents of the “Ink” text and use this to convey some basic theoretical knowledge. In China's printing industry, not only practical experience but also theoretical knowledge is needed. Not only should you know the terminology and vocabulary, but you should also understand its true meaning and laws. In fact, theory can guide practice. ("Chinese Printing")