Unpredictable and unwanted, moiré can devastate your halftone and process-color work. A collection of recommendations that you can use to make moiré go away...
When you screen print halftones, you can count on moiré. No matter how careful you are, the dreaded patterns will appear in your prints from time to time. You may go for months without experiencing moiré problems, then get hit with a rash of images in which moiré seems uncontrollable.
After printing halftones and process color for nearly 30 years, I have come to the conclusion that the problem of moiré cannot be entirely eliminated using current technology. But you can take steps that greatly reduce the occurrence of moiré in your prints. This month, I'd like to share ten practices that you can use to help keep moiré at bay.
1. Be systematic and organized.
This is the critical beginning point upon which everything else is built. If you are not systematic in your approach to printing, you will be doomed to experience moiré. Systematic means keeping track of everything. Eventually, you will be able to narrow the variables you have to observe. But in the beginning, there is no substitute for good records and organization.
If you do not have a data sheet where you can record screenmaking parameters, press settings, and other aspects of the job, make one. Keep copies of the sheet on clipboards posted in the art department, the screenroom, and at press side. When moiré occurs, record every detail about the current job parameters. The systematic organization of data will allow you to identify patterns of occurrence, and the written record will make it easy to spot similar circumstances that might be responsible for the moiré
2. Work from a constant set of values.
When producing halftone images, keep all production variables constant. Use the same set of halftone angles each time you do the same types of work. Use the same line count. Keep mesh tension within ±1-2 N/cm, and use mesh with the same mesh count and thread diameter from the same vendor. If you randomly substitute variables, it's like being lost in the forest when night is falling. Standardization is critical in helping to identify the problem areas that lead to moiré.
3. Never assume that what you have is correct.
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