Ink Performance Test.
The properties of ink include raw material properties and film properties, including water content, permeability, relative density, surface tension, PH value, viscosity, fineness, initial drying property, absorption property, adhesion fastness, anti-adhesion property, flow property and so on. The properties of the film include color, gloss, coloring power, light resistance, sun resistance, temperature resistance, aging resistance and so on.
Common performance testing methods.
1. Detection of ink viscosity.
In gravure printing, the control of ink printing viscosity is very important, especially in medium and high speed printing, it is directly related to pigment transfer, dirty plate, printing luster, electrostatic phenomenon and so on. At the same time, it is also the key to ensure the stability of printing color. The viscosity of ink can be measured by viscometer or viscometer, the commonly used viscometer / cup has rotating viscometer, Stormer viscometer, viscometer and so on.
2. Detection of Ink Gloss.
Ink luster is mainly in the printing surface after the light, the ability to reflect in one direction. The quality of ink glossiness will have a greater impact on the appearance of printed matter, good glossiness is bright color, poor glossiness is dim color. The gloss of ink is measured by gloss meter.
3. Ink color detection.
Printed matter gives people the most obvious feeling, is its color, bright degree and reflect the authenticity, in addition to the structure of the pattern, printing level, almost mostly by color to express. Therefore, the color of the ink test is very important.
There are two main methods to detect the color of ink: one is the instrument inspection method, which is determined by reflection densitometer and colorimeter. Another conventional inspection method, it is the ink coated on the printing material for comparison and judgment.
The methods of coating on the printing material are as follows: 1 razor scraping method. 2Ink roller coating method and silk rod method. (3) the method of printing with printability testing machine.
4. Detection of ink fineness.
The fineness of the ink refers to the size of the pigment (including filler) particles in the ink and the uniformity of the pigment particles distributed in the binder. After the ink is diluted, the particle fineness and distribution are measured by the scraper fineness meter.Expressed in microns (representing the maximum diameter of ink pigment particles).
5. Detection of Coloring Power of Ink.
Coloring power refers to the extent to which one ink affects the color of another ink. When blending spot color ink, when the hue of one of the primary inks changes, the color of the spot color ink will change. For example, when the hue of the original ink is more yellow than before, the spot color ink will have the effect of increasing yellow; if the coloring power of the red ink is strong, it will have the effect of increasing red.
GB/T 14624.2-2008 "Test method for Coloring Power of offset Printing Ink" should be used to detect the coloring power of printing ink.
6. Determination of adhesion fastness of printing ink.
Ink adhesion is the fastness of ink adhesion to the printing surface, if poor adhesion and fixation is not good, there is no certain fastness, not resistant to friction, not resistant to impact, not resistant to fatigue, that is, there is no printing.
There are five test methods for testing ink adhesion fastness:
1) scratch resistance test.
Apply moderate pressure with the fingernails of the thumb and repeatedly scrape the ink layer that has been printed and dried on the film. If the ink layer is scratched or the ink falls off, the adhesion of the ink is not ideal.
2) Tape peeling test.
Use viscose tape to evenly stick to the printing sample, press it with your fingers on the back of the tape to make it stick firmly, and then hold both ends of the tape with your hands to pull up at a medium speed to observe the ink sticking up by the tape.As long as there is ink on the tape, it shows that the adhesion of the ink on this kind of printing material is not good.
3) dry friction test.
The printing surfaces of the two samples are stacked together relative to each other, applying a pressure of 2 to 4 pounds of repeated friction, and scratches or ink shedding indicates poor ink adhesion.
4) the wet friction test method is similar to the above dry friction test, except that a little water needs to be added between the two prints.
5) Test of detergent resistance.
Drop one or more drops of alkaline detergent on the printing sample, suck it clean with paper towels or clean soft cloth or clean soft cloth after 15 seconds, and then wipe it with medium pressure. If there is any change in the printed picture and text part, it indicates that the adhesion of the ink is not good.
7. Detection of initial dryness of ink.
Ink drying refers to the ink from liquid to semi-solid, no longer flow transfer, that is, the ink "fixed" stage, is the initial drying of the ink.
Ink dryness test method recommended GB/T 13217.5-2008 "liquid ink dryness test method."
8. Detection of pH value of printing ink.
The pH value of ink is directly related to the printing suitability of water-based ink, such as viscosity, dryness and so on. There are two commonly used pH detection methods: ph test paper method and acidity meter method. Although the data measured by the test paper method is not accurate enough, but the operation is simple, it is a commonly used detection method in practical production. Acidity meter, also known as PH meter, is a kind of instrument for measuring pH value of solution by potentiometric method. The measured data of acidity meter is more accurate, and it is an ideal method to measure pH value.
Ink viscosity test is generally used to test the ink viscosity instrument to test the size of the resistance of the ink thin layer separation or torn apart, in order to represent the ink viscosity.
10. Detection of Ink Surface tension.
Surface tension is the ability of the liquid surface to contract automatically in the air. Ink surface tension will affect the leveling of ink, adhesion settings lead to failure in printing. At present, surface tension is generally used to detect surface tension.