Best Screen Printing Pre-Press Practices
Screen printing: One of the greatest businesses ever… or at least we think so. It’s a lot of fun working in this trade, from printing cool logos and designs and adding neat effects like foil or high density to creating a clothing line or just making a little money. We can’t speak for everyone, but there is nothing like standing over a freshly printed shirt after many man hours and being awed by the finished product. All that hard work was worth it. Every minute.
Arriving at that proud moment requires a delicate balance between pre-registration, substrate, frames, ink options, mesh selection, screens, chemicals and more, and that’s before printing even begins. Accordingly, we set out to shed some light on a few of the potentially passed-over pre-press procedures and considerations, without which our own success wouldn’t be possible.
Pre-press is the most important part of the process; any break down here has a domino-effect on the rest of the job. There are many systems and products that come into play in pre-press rooms, and it starts in the art room with film and output devices and moves to posting art films on carrier sheets and pre-registration systems. My best short advice in this area is to do your homework: Find the best systems and products that suit your shop within your budget, dial them in and get the max out of it all. A quick example is a pre-registration system. If the entire process is done correctly, a multicolor job should be able to be set up on a base plate with possibly only a few screens needing minor adjustment, if any at all. Set up sloppily and everything ends up all over the place. The adage do it right or do it twice has never been more appropriate.
Screen printers often overlook the importance of the darkroom. Usually this is the most neglected part of the shop. However, it is one of the most crucial. First and foremost, it is a must to keep the humidity low in the darkroom. A quality humidity tester that can be found at a local hardware store is a good investment. If the humidity is too high in the screen printing darkroom, the emulsion will not stick and dry to the screen properly.
Degreasing mesh is also essential. This is an area in which some printers try to use sub-par products. Good environmentally-friendly, inexpensive degreasers are available and will spare headaches during the washout process. Degreasing allows the emulsion to adhere to the mesh. Overuse may pose adhesion issues for the emulsion. For example, a 20″ X 24″ frame should only take two sprays of degreaser, one on the inkwell side and one on the textile side. Also, do not forget to degrease the sides of the frame as these hold contaminants just as much as the mesh. Where emulsion is concerned, a dual-purpose product works well in conjunction with water-based and plastisol inks. If printing with special-effects inks (high density, puff, glitter), use a high-solid emulsion.
It is also very important to properly dry a screen after the coating process. With the goal of building a gasket of emulsion on the screen, dry screens parallel to the ground with the inkwell side facing the ceiling.
Laying the framework
There are a variety of frames available for the choosing. Just starting out, consider static (stretch and glue) for ease of use. Although wood frames are inexpensive, they tend to warp and, more often than not, cost more to ship than aluminum frames because of the weight. Another tool necessity in this business is a high-quality tension meter, which reads the newtons (tension or tautness) of the mesh. A saggy screen can lead to ink transfer issues or image distortion problems, and a frame reading 11 newtons or fewer will need to be re-screened. Another option is the roller frame. Fine prints work better on this type of screen, and additional advantages here include the ability to change the mesh count in the screen, hold extraordinarily high tension and higher print quality. While converting to roller frames, use a higher quality mesh so that the greater tension doesn’t break the screens.
Mesh count is very important in correctly printing a product. Screen Printing Mesh selection can make or break a job and be the difference between a beautiful print that runs easily on press without much break down and an order that halts every couple of shirts for troubleshooting. We recommend stocking a wide variety of mesh counts for the best chance of success. But having that selection is only part of it. Knowing how to use it is the other.
Screen Printing PrepFigure
The first consideration involves a look at the ink being used. The company behind every ink brand out there wants printers to use its product successfully, and most have vital information via website or hard copy by request, such as ink specs, with recommendations for ink usage, including what mesh count works best and the expected results. Keep this information on a spreadsheet and add to it as you go. Someday, you will have your very own mesh count bible.
The aforementioned wide variety of mesh counts should look something like: 13, 40, 60, 83, 110, 123, 156, 196, 230, 305, 355 and 380 with at least a couple of each (some more than others). If personal stock falls short, order the missing mesh counts and start playing around with them to find out what applications each is best suited for. See Figure 1, the mesh applications chart for a basic idea of substrate/mesh matches.
Follow, flow through
Options for ink also abound. Begin with a clear direction of the customer base and offering therein. Going after athletics, schools, corporate, small business, or pubs? A regular plastisol set is probably in order, as most standard customers are not willing to pay above-and-beyond for special types of printing.
On the other hand, branded apparel customers are usually willing to pay for something special, such as a soft hand, a foil highlight and glitter. Going down this road means stocking ink room shelves with a variety of specialty inks, water based and/or discharge products. For the team apparel market, printing on nylon warm-ups and polyester jerseys necessitates poly-blocking and nylon-compatible products.
Business will most likely have need for a little of everything and a lot of some things, and the best bet is to make friends with brand representatives. Send them samples of some good prints, as well as those that don’t look so good and ask for recommendations.
Always keep in mind that there are 10 ways to do anything; determining which works best in your shop may require some trial and error, and that’s okay. After all, some of the greatest prints start out as experiments and coming up with something new keeps the passion flowing.