User login

Tools and Techniques for Economical, Environmentally Friendly Screen Printing

(May 2004) posted on Mon May 24, 2004

This article explains ways to keep your employees and the ecology safe while boosting your company's efficiency.

click an image below to view slideshow

By Andy MacDougall

I have a confession to make: I'm a recovering lacquerhead! I might as well come clean with all of you--my indoctrination into this business included plenty of baths in lacquer thinner and other chemicals in a lot of dark, poorly ventilated, ink-splattered printing shops. But it was these experiences that drove me to start cleaning up my act and im-prove conditions in my own shop over the last few years. Toxic, polluted, dirty workplaces have long been the downside of a career in the screen-printing industry. Over time, we may become used to the conditions, or immune to them, but the fact is that, as in industry, we have a collective case of shop B.O. Unfortunately, this is the stereotypical perception that John Q. Public has about all screen shops, and those of us who want to attract new workers must fight hard to change it. Even people who get a taste of screen printing in high school or college usually end up labeling it as "that stinky process." Not a very good first impression. The simple fact is if you continue to ignore your responsibility to clean and improve your work environment and waste streams, sooner or later this neglect will catch up with you or your employees in the form of a workplace injury, an environmental assessment or penalty from a government agency, or maybe even some kind of chronic respiratory, circulatory, or epidermal problem. Competition might not kill you, but failure to constantly adapt to new materials and processes will. Here's a prediction: Employees will not continue to work in unsafe conditions, and environmental-performance standards will only get more stringent. So will you wait until a lack of workers or a stop-work order shuts you down, or are you going to start to change now? Don't be put off because you can't afford an automatic screen-reclaiming system or a complete shop retrofit to an inline multicolor press with UV dryers. Even with limited resources, you can improve air quality inside your shop, reduce your energy and material consumption during production, cut back the amount of waste going into the local landfill or down the drain, and, as a bonus, improve employee health. Time for change A decade or two ago, terms like environmentally friendly and non-toxic would not jump to mind as characteristics of even the cleanest screen-printing plants. But in attending trade shows and visiting some larger shops over the last few years, I've seen some great strides in cleaning up solvent-emitting ink systems, volatile-chemical use, and other processes used in screen printing. This mostly involves switching to UV-curable or water-based inks and introducing automated screen-reclaiming systems. But that's just part of the story here. A perfect, non-toxic print shop would have zero air impurities, and all inks, additives, and other materials used would be biodegradable and non-hazardous. Drinkable water would flow from the drain systems. And nothing would leave the plant except printed products-- no garbage or byproducts. A dream, or a goal? In my opinion, we are nowhere near reaching that perfect goal today, in screen printing or in other areas of our lives. North Americans are still number one worldwide when it comes to water and energy usage, as well as garbage production per capita. However, I think we as a society are genuinely trying to make our environment better, and I know we are as an industry. Creating a less toxic and more green workplace simply requires a desire and a willingness to change materials and learn new procedures. With that in mind, I'd like to provide some practical suggestions to readers with more conservative budgets who are ready to rethink, reduce, recycle, and reuse. Prepress Let's start with prepress. When making film, you can eliminate photo chemicals by dumping the camera and using a thermal imagesetter, or better yet, an inkjet printer. There are now plenty of specially treated inkjet films that you can use to produce good positives at a fraction of the cost of high-end imagesetter output. If you're one of the many screen printers already running a large-format inkjet for print production, slap a bulk-black-ink feed bag on that horse and ride it. Inkjet positives may not be perfect for all applications, but screen shops that don't bring digital imaging in house and start learning how to use it today will be left in the dust tomorrow. A machine that can produce saleable full-color, short-run products and cheap film positives--what's not to like? If you run a high-volume shop that makes hundreds of screens per day, maybe it's time to investigate some filmless systems and do a cost-benefit analysis. You may not be able to afford a complete computer-to-screen imaging system, but there are other options that remove the need for making large film positives, including direct projection. Screen exposure Exposing photostencils with conventional, high-output UV lamps is a process that sucks a lot of juice. Other than UV or electric dryers, this is probably the largest single consumer of energy in a screen shop. Are you aware that solar energy (the sun) does a dandy job of exposing screens? Using sunlight for exposure is an unconventional approach, but it can be very effective and fast under controlled conditions (Figure 1). Shops that print flat graphics, es-pecially in southern climes, can use this method and save both money and time. You can do a 4 x 8-ft screen--or bigger--in a minute with the proper setup. I use my solar-exposure system for everything, including process-color halftones, and I only use an exposure lamp in the dead of winter or at night. If exposing with solar energy is a little too extreme for you, then consider switching to a faster emulsion, either pure photopolymer or dual cure. These will cut exposure times substantially, saving energy and speeding production. Washout and reclaiming Your options for improving this area really depend on your budget. At the very least, your stencil remover, haze remover, and degreaser should be bio-degradable. Read the label or ask your supplier for some samples, then switch to the one you find most effective. Many shops only use high-pressure washers and skip the harsh chemicals altogether. Another alternative for reclaiming smaller screens is to use passive dip tanks with reusable, low-tox chemicals. After the stencil and ink residue are loosened by submerging the screen in the tank, a quick pressure wash completes the reclaiming process. Automated, enclosed washers use jet sprays and recycled chemicals to do the same thing. They are much more expensive, but they have the added benefit of a complete, closed-loop system, which keeps cleaning-chemical overspray out of the shop air. If you're limited to cleaning screens in a washout booth, adding a suction vent to the area will help remove overspray and airborne contaminants and reduce humidity fluctuations. With any washout system, you should filter solid waste instead of flushing it. An easy, do-it-yourself method is to run your waste water through a settling tank with filter baffles made of old screen mesh. Commercial filtration systems work in much the same way, using removable or replaceable staged filters for the different sizes of particles, or passing the water through a special paper filter on a continuous roll. Once dry, the collected particles and the filter material can be safely disposed of in a landfill. With some filtering systems, a flocculant is added to waste water to attract particles and clump the materials into a solid mass that dries to a cement-like consistency, ready for disposal. Personal safety equipment If you can't eliminate exposure to inks, cleaners, or other chemicals, you can get properly dressed for the occasion and create a barrier between yourself and any nasty or irritating substances (Figure 2). For washout or screen reclaiming, wear solvent-resistant gloves, apron, long-sleeve shirt, face splash shield (or at the minimum, safety goggles), and respirator (if necessary). And don't forget ear protection when running a pressure washer or other noisy equipment. Speaking of noise, it is a form of pollution, too. Where appropriate, move compressors or vacuums out of the work area, and run air lines to your equipment. Ink alternatives When it comes to ink selection, UV inks are the most environmentally responsible option, provided your applications are compatible with this type of ink. UV inks contain no VOCs, cure rapidly with exposure to UV light, and enhance a shop's overall productivity. Be aware that UV inks can cause allergic reactions in a small percentage of people, but that these occurrences are quite rare. It's something to keep in mind if you're adding this ink system for the first time. Another alternative is switching to water-based inks. They allow you to use water for cleanup and thinning. Water-based ink can almost eliminate VOCs (volatile organic compounds) in the printing and reclaiming areas of your studio, and it minimizes use of screen-reclaiming chemicals. A bonus with water-based inks is that you can use the same sponges over and over for cleaning and eliminate the cost of rag consumption and special cleaners. If you do use solvent-based inks, switch to citrus- or soy-based ink degraders and cleaners. Doing so allows cleanup without lacquer thinner or other volatile solvents, and it makes your workplace smell a lot better. If you just can't give up your lacquer thinner, use a respirator mask (Figure 3), wear solvent-resistant gloves during cleanup, and put used rags outside the workspace in a fire-resistant container. Use a rag service to remove and recycle used shop towels. To help minimize VOCs and solvent odors, make sure to locate intake vents for the ventilation-system near the floor because solvent fumes are heavier than air. Conveyor dryers should be vented to the outside, but consider running a portion of the venting along an inside wall as an alternate heat source during winter. Ink removal Tape out your screens with clear packing tape or a similar product. Tape your gutters and into the screen surface close to your image. At the end of the run, pull a final thick flood stroke, then your last print. This will scrape the stencil clean, and 99% of the excess ink can be easily scooped from the tape. Just pull away the tape before cleaning. This eliminates excess ink cleanup on the press or in the washout booth. Use ink knives (or cake spatulas) instead of cardboard scoop cards to reduce waste, and scrape away as much ink from the stencil area as possible. When cleaning solvent-based materials, make sure to use enough cleaner to break up the ink and absorb it. If you're careful, you can use a single rag to clean the screen, wipe the squeegee, and then clean the ink knife and any spills. Always clean tools and equipment before inks or spills harden. You'll use much less cleaner and wiping material. A breath of fresh air Smaller shops should consider in-room air scrubbers to remove VOCs and dust from the air through replaceable filters. These are available in different sizes to match the volume of air in a work area. The advantage air scrubbers have over direct exhaust fans is that they keep your in-shop temperature and humidity constant, minimizing heating and air-conditioning costs. In some cases, the ability to pull dust, ink particles, T-shirt fluff, and other contaminants out of the air before they mess up a print is as valuable as the clean air itself. If you can't afford a store-bought air-filtration system, here are some other suggestions: Separate dirty processes from the main printing area and build your venting to accommodate the layout, with sealed spaces if appropriate. If you really want to get crafty, build the venting so you have positive air pressure in the printing area at all times, with a controlled, filtered intake. This will decrease dust in the area and carry away VOCs, smells, and airborne particles quickly. Localized suction hoods for drying racks, or exhaust venting near presses, will carry off the bulk of evaporating solvents from the immediate work areas. You can also pump fresh air at low velo-cities to each workstation on the production floor. Whose turn to take out the garbage? Instead of dumping your shop's refuse all into one container, separate your waste stream into used ink, paper, cardboard, plastic, and absolute garbage. I can recycle four out of five of these materials at no cost in my community, and I'll bet you can, too. You just have to take the time to separate it. Here are some more tips: * Mix used darker inks together and use the mixture as black or dark gray, and try to use leftover custom-mixed inks before new ones in subsequent prints. * Recycle paper for setup and test prints, and then use it for wrapping or packing material. * Reuse cans and plastic containers for ink mixing. * If recycling services are limited in your area, strike a deal with a local school or youth center--you'd be surprised at how much of your junk could become valuable and treasured works of art. Clean living Lots of the ideas I've provided here won't cost much to implement, and in some cases, they'll actually save you time and money in the long run. Don't be afraid to rethink your approach to production--look around your shop and see what you can do to clean up your act. Make a list, take it one step at a time, and ensure your employees buy into the reasons for changes and the systems required to make them work. Don't just tell them what to do, show them. Reduce your use of chemicals, solvents, rags, inks, water, and power. Recycle paper, cardboard, metal, and plastics. And reuse paper, inks, cardboard, sponges, water, containers, and screens. There really is no such thing as "non-toxic" in life. Even water will kill you if you ingest too much of it. However, you can easily achieve low toxicity in your print shop by analyzing your methods and materials, researching new products and systems, and making appropriate modifications to your production methods. The goal is to still put out a good product without sacrificing quality or profit. The bonus is a healthier workplace for yourself and co-workers and a cleaner, greener world for us all. About the author Andy MacDougall operates a screen-printing studio in the Canadian city of Courtenay, British Columbia. From a start as a printer's apprentice his background grew to include positions as a marketing and sales director for a multinational graphic-equipment manufacturer and a printing-business owner. His current focus includes printing limited-edition art, developing low-toxicity print practices and techniques, conducting workshops and training seminars, and consulting for manufacturers. Visit him online at


Did you enjoy this article? Click here to subscribe to the magazine.