Using a loupe to check for errors makes for a good method of identifying flaws and making improvements in the printing process.
Laser printers will often create smaller dots that look like little piles of sand loosely grouped together as the toner particles are fused to the page. Obviously this type of dot will not create the best dot on an exposed screen because the image will not wash out very well. It will also contribute to dots that have a higher surface tension and a tendency to pull ink back off of the shirt rather than leave a clean print. This can snowball and create a situation where the printer must increase pressure to get the ink to clear out of the screen, causing dot gain in the halftone to gain significantly over a print run. Add this issue to a touchy burn time from vellum films and it can be a real challenge to get halftones on press that will behave the way that they should during volume printing of shirts.
A group of halftones produced inaccurately may have a secondary pattern or distortion and additional holes in the film’s black areas (Figure 3). In this case, software issue may be creating dots that have additional, incorrect, and unnecessary holes in the recreation of the halftone patterns. This problem may be invisible to the naked eye but will be readily apparent when viewed under a loupe. Once again, a true copy of the best reproduction your equipment can produce is necessary for a clear comparison.
Checking the screens before coating
Screen printers may look puzzled when asked if they examine uncoated mesh that has been stretched onto a screen though a loupe. They may think, “What could possibly be an issue with a screen that doesn’t have emulsion on it yet?” The truth is, there are many reasons to look at screen mesh before coating with emulsion. The most common are thread diameter vs. open area, mesh contamination, and weave angles.
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