Blanket is the intermediate for the transfer of offset printing ink. The quality of the blanket directly affects the quality of the printed matter. And blankets are expensive, and replacing the blankets too much during the book printing process is undoubtedly a disguised increase in the cost of the product.

When selecting a blanket, the elasticity of the blanket, ink transfer performance, corrosion resistance, penetration resistance, and flatness are the five most important factors to be considered.

1. Elasticity

The moment the blanket leaves the embossed area, the deformation due to the printing pressure is restored. This is the most basic and important technical requirement for the blanket, which determines whether the printing ink can be transferred normally.

The blanket cylinder is located between the impression cylinder and the plate cylinder. When book printing, each unit on the blanket should be contact with the two cylinders once during the rotation process, that is, twice deformation due to the printing pressure, and at the same time the process of transferring the ink from the plate to the blanket and then transferring it from the blanket to the substrate. Assume that a sheet-fed offset press prints normally at a rate of 10,000 sheets per hour. Each unit on the blanket is then compressed and deformed once every 0.18 seconds, and it is required to be able to recover its deformation before the next (0.18 second) deformation. High-speed rotary press blanket deformation recovery time requirements shorter. If deformation cannot be restored, each unit on the blanket can no longer transfer ink to the substrate after transferring ink from the plate to the blanket, or after transferring the ink to the substrate. The ink transferred from the plate cannot be accepted, and the printing process cannot be completed.

2. Ink transferability

Ink transferability is another important technical requirement for rubber blankets. It is often measured by the ratio of the amount of ink transferred from the blanket to the substrate and the amount of ink transferred from the plate to the blanket. Gaoyue is conducive to the transfer of ink. The poor ink transfer performance of the blanket causes the ink to accumulate on the blanket, increasing the number of times the blanket is cleaned, and at the same time, the operator mistakes that the amount of ink is too small to increase the amount of ink, thereby wasting a large amount of ink. For printed matter, the dark tone of the image is not deep enough, the density in the field is not enough, and the high-profile level is lost, which seriously affects the quality of the product.

3. Corrosion resistance

The fountain solution used in the printing process is generally weakly acidic and may be alkaline due to the formulation. Both acidity and alkalinity have a certain amount of corrosion, and the fountain solution is often transferred to the blanket through the plate, which requires the blanket to have a certain degree of corrosion resistance.

4. Impermeability

All kinds of inks contain a certain amount of auxiliary materials. After infiltrating the blanket, it will expand and fall off layer by layer, which will affect the service life of the blanket. This requires it to have a certain anti-penetration performance.
5. Flatness
The so-called flatness refers to the uniformity of the blanket thickness, error often requires within tens of microns. Excessive errors often result in unstable ink transfer, uneven ink prints, and dot distortion. Therefore, the flatness is particularly important for offset blankets.