New Theory of Testing Method of Ink Properties

In the production process of printing, it is very important to test and control printing inks. The attention to the properties of inks can ensure the consistency of batches of products, and also allow us to analyze and predict the printing suitability of the inks after they are put on the machine. As the printing industry grows into a mature industry, new testing technologies and instruments also emerge.

Tests for offset inks generally include: tack, stability, viscosity, yield value, wet lapping, abrasive particle size, and other tests. These tests are primarily directed at the physical properties of the ink and have a direct relationship with the performance of the ink on the press.

The tests to determine the value of a certain ink and its properties after printing include: color, strength, gloss, abrasion resistance, product resistance, fade resistance, etc.

Instruments used to measure these characteristics typically include: an inkometer, a Laray viscometer, a Duke wet lapping tester, and a mill. Other tests use a spectrophotometer, a gloss meter, a Sutherland abrasion tester, or a CAT abrasion tester, and a Fade-O-meter fade tester.

All of these test methods still play a valuable role in controlling ink quality, but there are some applications that are more suitable for newer test methodologies. Let's consider the interaction between ink and fountain solution during offset printing. The wet pull test is of course very useful. It is also important to understand the dynamic surface tension of the water fountain solution and its effect on the ink-covered surface. This test can be done with the SensaDyne Surface Performance Tester, which can help determine the surface tension by measuring the maximum foaming pressure.

Some people may think of this suggestion when using a hydrophilic plate. Because the plates are hydrophilic, they are very sensitive to the solution in the bucket - sometimes, the images on the plate are very prone to inking. Therefore, the image material should have great water resistance. So how do we measure the hydrophilicity of the material? One method is to measure the contact angle. Using an instrument called a goniometer, we can measure the contact angle of the liquid. We can measure the contact angle of the liquid formed in contact with the image (or non-image) portion of the plate. The ratio of the surface free energy of the image area to the non-image area is a very important factor in determining the cleanliness and clarity of the print results. If there is evidence of high surface energy in the image part of the material, it means that this part will be preferentially wetted by water rather than covered by ink. In this way, we may obtain low-grade printing quality and produce images that do not get inked.

One variation of the contact angle test method is that it can also be used to test the wetting of liquids on other webs. Assume that the surface of the paper is slowly absorbed by the fountain solution, which interferes with the transfer of ink to the surface of the paper. How do we determine the absorption rate of the hopper solution to the paper? One option is the FibroDAT (Dynamic Absorption Rate Monitor), which provides us with a video image of the droplet volume, and the contact angle at which the droplet initially lands on the paper. As the absorption process occurs, the change in droplet volume is measured. The computer was used as an analysis to determine the relationship between the two materials.

Occasionally, we believe that the wet-skinning properties of inks are related to its offset suitability. However, in the measurement of the amount of water the ink can withstand, the relatively primitive method produces a confusing result under our estimated potential problem. Therefore, the more important factor is the effect of ink emulsification on viscosity, fluidity, and ink shortness. Because these quantities determine the ink transferability to the plate and media. The cone-plate viscometer used to measure the difference between emulsified inks is used to detect significant changes in viscosity and ink shortness, or on the operational performance of the machine.

The last test instrument is also a very useful tool in determining the effect of temperature on the viscoelastic properties of the ink. This is a very important aspect of waterless printing. On waterless printing plates, the main problem with tone reproduction is that due to temperature rises, ink failures and image images lose their neat effects. Rheological properties can be used to measure the rheological properties of the ink under high temperature conditions.

Transfer from: Wins