Five Important Technical Indicators of Offset Printing Inks (Down)

Third, the dryness of the ink

The drying process of offset printing ink on paper is the process in which the ink changes from a non-polar colloid with a high fluidity to a fixed state. Generally, there are two indicators for measuring offset printing inks:

1. Fixation speed It means that the ink changes from a natural flow state to a semi-solid state. That is to say, the printed product is not sticky when it is superimposed on a certain height, and it is called initial drying on printing. The initial drying of the ink is determined by the resin structure chosen in the design. The initial drying time is short, but not completely dry.

2. Oxidation and conjunctival drying is the dryness mentioned in printing. The drying time is longer, usually more than 8 hours, and it is completely dry. The complete drying of the ink is determined by the type and amount of the desiccant, which can be adjusted within a certain range.

Offset Printing Ink

At present, offset printing inks are all resin-based and have a fast fixing speed. Theoretically, the faster the initial drying, the better, but too fast initial drying will affect the gloss of the printed matter. The operator of the offset press always hopes that the ink printed on the paper will dry quickly, but it is impossible to dry it in the ink fountain. Generally, about 80% of the ink conjunctiva drying time is between 16 and 30 hours. If the conjunctival drying time is too short, it is easy to cause skinning and holding rollers on the machine, printing general coated paper or long plate printing, you can choose the ink with longer conjunctival drying time. For high-grade coated paper, jammed paper or short-run paper, you can choose a fast-drying ink.

Fourth, the gloss of the ink

The gloss of the printing ink for offset printing machine is the ratio of the amount of light reflected by the regular print to the amount of light reflected by the standard plate under a specific light source and a certain angle of illumination. The brightness of the print gives a direct impression. Generally speaking, the higher the gloss feeling, the better the printing effect. Although the gloss of printed matter has a certain relationship with the wetting fluid used in printing and the absorbency of paper, it is mainly determined by the ink. This property of the ink depends on the binder and pigment. The binder and pigment in the ink should have good printability, and the resin itself should have high gloss. Such inks have high gloss on the paper. Good gloss inks tend to dry a little slower on initial drying. When printing on a monochrome machine, the ink with a high gloss must control the overprinting time, otherwise the phenomenon of ink crystallization is prone to occur.

Five, the fineness of the ink

The fineness of the ink indicates the size of the pigment and filler particles in the ink and the uniformity of the distribution in the binder. The fineness of the ink is directly related to the nature of the pigment and the particle size. The better the fineness, the more stable the nature of the ink and the fuller and stronger the dots of the printed product. On the other hand, in printing, it is easy to have disadvantages such as low printing resistance, ink stacking, empty dots, expansion, and unclean dots.