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4 2 G R A P H I C S P R O • J A N U A R Y 2 0 2 3 G R A P H I C S - P R O. C O M S C R E E N P R I N T I N G N othing else in screen making can compare to the frustration of not being able to get all your halftones burned out properly. Exposure times coupled with differ- ent ink densities in your output printer only adds to the frustration. And for some, trying to decipher terms like RIP and LPI only adds to that confusion. So, let's try and wade through those muddy waters with the basics. With conventional halftones you either need to use an art program to generate halftones or from some type of RIP software to either make a film positive of your artwork or use direct-to-screen (DTS). en, you must expose your screen and wash your image out. Inside Corel, Adobe or your favorite separation/RIP software you will have the ability to set your halftone frequency (LPI) and your half- tone angle (0-90). e LPI simply means how many dots can fit in an inch, so the bigger the number, the smaller the dot. How small a dot you can make is dictated by what screen mesh you have and what you are printing on. e math for mesh selection is your DPI x 4.5. So, if you wanted 50 LPI then you need to have a 225-mesh screen. Every school that teaches screen printing will tell you to make your angle 22 degrees, it is a magic frequency that helps reduce moiré (unwanted patterning). On garment selection, large ring-spun cotton does not take halftones very well as it will try and print on the peaks, the valleys will miss, and you can lose a lot of detail. I suggest starting out at about 45 LPI until you get the hang of it. en you can work your way up 75 LPI later on. Screen prep is super important, and you will need fresh emulsion that is evenly coated on the screen, along with sharp film positives and dense black ink. Make sure you have an exposure calculator and expect to waste a screen or two testing when you first start out. Be patient in your rinsing and make sure to post-burn the screen. Another option that is quickly gaining in popularity is to use a Riso ermal Screen Maker from Xpresscreen. e mesh is already coated with a PET coating and a ther- mal printhead burns the screen wherever ink should go through. It eliminates water, emulsion — actually, every aspect of conventional screen making with perfect half- tones every time. No film needed, and it has its own onboard RIP. GP DON'T HATE ON C O U R T E S Y O F X P R E S S C R E E N I N C H O W - T O / T U T O R I A L Make sure you have an exposure calculator and expect to waste a screen or two testing when you first start out. Every school that teaches screen printing will tell you to make your angle 22 degrees; it is a magic frequency that helps reduce moiré (unwanted patterning). A Riso Thermal Screen Maker eliminates water and emulsion. The mesh is already coated with a PET coating and a thermal print head burns the screen wherever ink should go through.