March '15

For the Business of Apparel Decorating

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90 | PRINTWEAR M A RC H 20 1 5 heaters that only heat humid air, but if the warm, moisture-laden air has nowhere to go, it's just hot and humid, like a rain forest. Fans circulate air, but circulating humid air isn't much help. Dehumidifiers can be of assistance, but think of how much moisture you need to remove from your screen-drying area. Does a dehumidifier remove enough humidity? Remember, while many screens dry at the same time in July in Florida, it creates a lot of water. Don't think Minnesota in Febru- ary is exempt, either. You have to identify how much humidity you're dealing with, and that is done with a hygrometer. Humidity levels are affected by many factors—from different times of the year to how busy a shop is and how many screens cycle through. Hygrometers are available at most Radio Shacks or home and kitchen stores for a small investment of $25 to $50. A proper humidity measurement is around 32 percent, but if you shoot for under 40 percent, you should be in good shape. Con- sider that humidity also factors into the proper running of many direct-to-garment and embroidery areas. EXPOSURE CALCULATOR Usually, there's a starting point where the print practitioner exposes and evaluates, and he or she repeats the process until it's correct, often with several wrong guesses in between. An exposure calculator, how- ever, takes much of the guesswork out of exposure times, and most emulsion man- ufacturers have one. This device is a fil- tered film positive with usually five filters at 100 percent, 75 percent, 50 percent, 33 percent, and 25 percent, all with gradient dots and type sizes. The typical guideline is to double the esti- mated time. Let's say you estimate five min- utes as you expose the screen with the ex- posure calculator on the print side. All five filters give you a test of five times at once: 100 percent at five minutes, 50 percent at 2-1/2 minutes, 33 percent at one minute and 39 seconds, and 25 percent at one min- ute and 15 seconds. After washing, you can check the clarity of dots and detail of each time frame for un- derexposure and overexposure. Remember to check the squeegee side for each time and image, feeling for indicators of underexpo- sure. On diazo and dual-cure emulsion, PRINT SHOP TOOLS A laser temperature gun reads the platen and flash temperatures as well as spot checks at the end of the dryer for the surface ink film temperature. (Image courtesy Tech Support Screen Printing Supplies) A laser temperature gun reads the platen and flash temperatures as well as spot checks

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