Printwear

October '13

For the Business of Apparel Decorating

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Printwear 2013 Q&A Screen Printing in your shop with your supplies. Testing devices will help to get to that point; the testing device to monitor that you are still on track is a washing machine. Most plastisol has to get to 320°F through the entire ink film in order to fully cure. There is no device on earth (that you can afford) that actually measures that. You can know your dryer temperature and belt speed, but what if your shirts are loaded with moisture (which will cool them off as it evaporates)? What about the day where the shirts in your cold shop are entering the dryer at 40 degrees in the morning, and you are using settings from the summer when they went in at more than 100 degrees? What about a thick ink film versus a thin ink film? Before the print get to the press, it's important to select the right mesh, emulsion and type of You can also stretch the ink on a shirt ink for the particular job at hand. (Image courtesy Lon Winters, GraphicElephants.com) after it has been through the dryer and cooled off. You'll eventually have a pretty good idea of what you see for cracking (it will nearly always covered with plastic or wax paper. That cuts the cost and makes crack) means that it is cured or not, but you'll need to wash the cleanup a breeze. shirts to make sure you are correct. Liquids are sold with different percentages of solids. So emulHere's another tip for those trying to figure out their dryers: sion that is 46 percent solids is 54 percent water. The screen turn the dryer temp up and slow the belt down until you scorch printer is paying to ship water that might freeze in the winter. the shirts, then turn the dryer temperature down until it doesn't Capillary film has no water. Screen printers who buy on price scorch any more. That will waste energy and those settings will frequently buy low percentage solids and think they are saving scorch shirts if the air temperature in your shop goes up signifimoney, when really they end up coating each side of the screen cantly, but at least you will know the ink is probably curing. And multiple times, and use more solids than the shop that bought a even then, at least take some shirts home and throw them in with high-solids emulsion in the first place. your wash to make sure the ink is cured. With the new liquid that is available today, we recommend shops pull the scoop coater up the print side of the screen only Rick Roth, Mirror Image Inc., theinkkitchen.com one time when the mesh count is 160 or higher. On a more coarse mesh, like 110, we recommend coating each side of the screen only one time. The new liquid emulsion is high percentI use capillary film. Should I be using liquid emulsion? age solids, exposes faster than prior formulations, bridges over The two are very different products. Each has advantages and the mesh better, and produces thinner, higher resolution ink dedisadvantages. First, we train everyone on capillary film, and not posits for softer prints. liquid emulsion, because it helps in gaining an understanding of Liquid emulsion makes sense for lighter colored shirts with the screen making process. large images. Dark garments need more dimension to the imCapillary films come in thicknesses marked on the package. age, and that is more achievable with capillary film. We, for Using a step wedge test, we can calculate very accurately just how example, print white ink on black cotton shirts using 110 mesh long the light must be on for full exposure. That is very helpful. and 50 micron capillary film without flash curing or printing Shops learn that bulbs put out less after substantial use, and the a second time. exposure time can be increased by 10 percent to compensate. The point is: liquid and capillary film each have Also, for example, when washing out screens with fine detail, their advantages. Shops need to know which will we under-expose by 10 percent to make washout easier, and then do the better job in a particular circumstance. post-expose. With capillary film, we use a piece equal to the image size and as wide as the squeegee. The rest of the screen is Roger Jennings, R. Jennings Mfg. Co. 88 | Printwear PW_OCT13.indd 88 October 2013 9/18/13 11:55 AM

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