How Do I Determine the Exposure Time for the Ps Plate?

The photosensitive range of the PS plate determines the exposure time. The light source's sensitivity and spectrum properties, as well as its strength and other parameters. As a result, whenever you switch to a different brand's PS version or change the light source, you must use the measurement and control strip to run a series of tests on the PS version to determine the proper exposure time.

How can I change the exposure time of the PS version based on the conditions?

1. There are no dots, only thicker writing. The original form of lines and solids can improve exposure duration, eliminate minor filthy spots and stains, and shorten cleaning time.
2. When the negative is stored for a long time, the blank part turns yellow, or after manual imposition, there are two or three layers of blank film bases superimposed together, which can slightly increase the exposure time; the original plate with low-density solid part can reduce the exposure time.
3. Because the pressure of the proofing machine is lower than that of the printing machine, the increase of the proofing dots is less than that of the printing dots, thus the exposure time of the proofing plate should be less than that of the printing plate. In general, 0.5% of the outlets are eliminated and 1% is retained for the proofreading version.

Strictly speaking, when defining the tone reproduction curve for color separation plate creation of layered drafts, the change in dot gain under different situations should be considered and corrected. In fact, because the standardization of this procedure in China is poor, the exposure time must be adjusted based on the manufacturing conditions of the individual printing factories. The exposure time can be increased if the dot increase rate is high during our factory's printing process. Depending on the substrate to be printed, the exposure time should be longer when printing the printing plate of offset paper than when printing the printing plate of coated paper.

What is the purpose of pumping air when printing and exposing?

Using the manufacturing of the positive pattern PS plate as an example, if the film surface of the negative film is not in close contact with the photosensitive coating of the PS plate, the plate will not print properly. If there is a gap in the middle, the light will shine obliquely into the picture and text from the edge of the blank section of the negative film. The photosensitive coating right below causes light to break down the edge of the graphic area, causing the image to blur. The dots shrink, and the small dots and thin lines disappear.

Because the printing frame has transparent glass on one side and a rubber pad on the other. When the vacuum pump pulls out the air in the printing frame, the air pressure inside drops, and the PS plate is released by the effect of the external atmospheric pressure. The original negatives are fused together and frosted on the glass.