Stand back and see what you can do to organize your shop processes.
A quality halftone print should display clear dots and solid coverage of the black areas while maintaining a distinct differentiation between the different levels of gray in the printed image. Test the different mesh counts to see which process variables will have to change to accommodate different thread counts. If the shop owner doesn’t want to invest in screens for every mesh to test, then at least test the most common underbase and top-color mesh counts in regards to detail printing (common underbase mesh counts are 140-160 threads/in. and common top color mesh counts are 230-305 threads/in.).
Printing standards beyond halftones
Once the halftone-gradient test standards are determined and a screen printer has a good idea what their best resolution, pressure, ink, and screens are, they can move on to test other variables in the printing process that can help with overall efficiency and eliminate costly scrap shirts.
Registration and trapping-distance test This process will show how well a printer’s equipment can maintain a print on all of the different platens available, as well as during a print run. A review of this two-color print test should show any glaring issues, and especially be noticeable if the automatic press is out of level (Figure 3).
The registration on a press may be problematic on an unlevel platen and sometimes may be different on each press head. Another issue is that a press that isn’t level will print some platens well or too dark and then others too light, or a specific platen that isn’t level may have a print that starts dark and then becomes lighter at the end of the print.
Testing halftone index dots Assuming that everything is acceptable from the rag-and-trap test, the printer can then move onto testing different types of halftones, such as index dots, to determine the highest resolution they can hold effectively for that style of printing (Figure 4). The advantage of using index dots is that with certain types of artwork, the square dot of an index halftone will maintain more printed surface area and retain some small details. Despite a grainy appearance, square dots can actually be very friendly to separate quickly and print well without a lot of dot gain during a longer print run.
Did you enjoy this article? Click here to subscribe to the magazine.