What are control strips?
The control strip is printed at one end of the sheet and its purpose is to provide the printer with a guide to the qualities of the print. Some printers edit and create special types of control strips for specific jobs, however, certain conventions are generally used standard. Among the most used are the Graphic Arts Technical Foundation (GAF), Fogra and SWOP.
Typically, a control strip includes full tones, tonal scales, frames (which primarily allow you to identify gain points) and registration marks at the ends and centers of the sheet.
How to choose the right control strip for my print?
In order to select the appropriate control strip, the following parameters must be taken into account:
- Maximum sheet width
- Number of keys for inking
- Width of the keys for inking
- Patch size that the instrument can measure
What are the types of patch?
- Solid patches are needed to obtain a measure of the density and color of printing inks. One is usually placed for each color to be printed.
- With respect to patches with weft, representative point percentages such as 25%, 40%, 50% 75% and 80% are usually selected, which help to control the point gain in the printing process.
- For selection jobs (CMYK), only trap patches are used. Those are composed of 100% of two of the three selection colors. This type of patch serves to verify that the mechanical characteristics of the selection inks are adequate when they interact with each other.
- In order to see print neutrality, gray balance patches serve as a reference. These are only used in strips for selection work and predominantly those used for G7 type certifications.
- The sliding and folding patches are used to determine the additional point gain that can be generated in the form due to a mismatch in the transport and reception of the sheets between printing units.
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