Difference between wet offset printing and offset printing

Wet offset printing is the most common printing process in the printing industry today. The basic principle is to use the ink balance between the printing area (printing ink) and the non-printing area (water) on the printing plate. The key is to maintain stability and control of the ink balance.

Waterless offset printing uses a silicon coating on the printing plate as a non-printing area to remove water and ink balance control and also eliminate the use of water as a medium.

From a print quality point of view, water is not used to print sharper and better print dots for waterless offset printing. Waterless offsets have the ability to achieve higher line counts and contrasts.

From the standpoint of print durability, wet offset printing is more compatible than waterless offset printing. Water can be considered as a cleaning plate, ink path, a bit like the self-cleaning function at the time of printing.

In water-free printing plates, dust and paper dust can damage the water-free offset printing silicon coating, making the selection of substrates and the cleaning environment of the work environment more demanding.

In general, waterless offset printing requires higher printer maintenance and operator skills. It's the slightest mistake in the process, and the quality of the print may change a lot. The problem of ink temperature, despite years of technical development, waterless offset printing is still a very complicated process. Every process requires perfect control to achieve high print quality.

At printing speeds higher than 150 meters per minute, wet offset printing requires a chill roll to cool the heat accumulated in the print block, which can affect ink performance and ink density.

Waterless offset printing requires cooling roller cooling at any print speed and cooling of the plate at the center of the plate because the ink temperature is extremely sensitive to controlling print quality. The working temperature of ink is limited to a very narrow range, only 3 ~ 4 °C. Depending on the supplier, above or below this temperature, the ink becomes unstable and the print quality is affected. In order to achieve better control of the printing effect, the air conditioning temperature control is required inside the factory.

From the point of view of consumables, there is only one supplier of waterless offset printing plates, and there are not many ink suppliers. Suppliers of wet offset materials are in fact numerous. As for the cost of consumables, since waterless offset printing is not available in the industry, the cost of consumables is significantly higher than that of wet offset printing. In some cases, inks and plates can be up to 3 times more expensive.

Waterless offset printing claims to reduce machine waste because it does not require treatment of ink and water balance. On the other hand, modern wet offset printing can be fully automated for ink and water treatment. It also makes water ink balance control more accurate and responsive, and is comparable to waterless offset printing. In fact, the process of controlling the ink will largely influence the performance of wet offset printing and waterless offset printing.

Since there is no water, waterless offset printing can achieve good printing results within a short printing turnaround time, provided that conditions such as temperature and cleaning must be met, and the basic parameters have been set correctly.

For substrates that they do not understand, wet offset printing still takes more time, resulting in more waste products. When repeating the same printing job on a known substrate, the advanced offset printing unit can store the existing ink parameters, can repeat printing, and its preparation time is shorter, similar to waterless offset printing.

Source: Packaging Expo

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