Here we are, finally at the end of the screen-printing production line. Our trip through the stencilmaking process has brought us to the step that we love the best–screen reclamation. We have all bought a really cool, state-of-the-art machine that allows us to load a screen caked with dried-on catalyst ink onto a conveyor belt and watch it magically come out, dry and ready to be retensioned or re-exposed. The chemicals we use are wonderfully reclaimed by the waste recycler and magically turned into fresh water, which is used to fill the aquariums of tropical fish in the boss’ office. Problem solved for you, and column finished for me. Gosh, that was easy wasn’t it? Hey, it’s a dirty job, but someone has to do it.
Actually, it’s not so easy. I suspect there are a few of us who still reclaim our screens the old-fashioned way. Ok, let’s get real. Most of us still use the same, basic, time-tested method who has changed little over the last 20 years. The chemicals have become more environmentally friendly and a little more effective, but the process is pretty much the same. Scrape the ink out, remove the tape, splash on the ink remover, slosh it around with a nylon brush, spray it down with water, splash on some emulsion remover and wait a while, pressure spray the broken down emulsion out of the mesh, dehaze if necessary, and then degrease, and you are finished. Pretty simple, isn’t it?
No, it’s really not that easy. I know that for most of us, this method often doesn’t yield the results that the chemistry supplier promised. It worked beautifully when the distributor visited to demonstrate the products, but it somehow never seems to work consistently once you put it into practice. The easy way out for we managers is to blame the person responsible for screen reclaiming assume that he or she is not following the correct procedure. We often decide that the inks we use are so specialized that we have to compromise, and every screen ends up being routinely dehazed, reducing screen life drastically.
We convince ourselves that the manufacturer reps used super chemicals when they sold us on their products, but we ended up receiving watered-down versions. I have heard that last explanation more times than I care to remember, but I have never seen any proof to back it up. As anyone who has reclaimed screens over a long period of time can tell you, it’s very easy to leisurely reclaim four or five screens to perfection during the two or three hour period it usually takes for a demonstration. It’s very hard to do it under the pressured conditions that we find in the average production environment. To do it effectively, we have to make sure that we have the right tools and the right disciplines in place. Now that’s not so easy, is it? So let’s get started.
Rules of reclaiming
The first rule of thumb is the reclaiming process should always be kept separate from other activities that involve water, and if possible, should be located far away from the screen-prep area. Every shop should have a minimum of two washout booths—one for reclaiming and one for washing out stencils and degreasing screens. This may seem very obvious, but I still see many shops mixing the two processes. It is literally like mixing oil and water.
If you don’t have two washout booths, then you cannot produce a decent stencil. Period. Think about it. When you prep a screen for the first time, can you guarantee that the chemical residue left in your shared booth will not splash back onto the screen? How can you get your emulsion to work properly if there is even a minute amount of emulsion remover left in the mesh? You might have been able to make it work reasonably well when you first began doing this years ago in your garage, but it won’t work now. It’s really not too hard to calculate how quickly another washout booth will pay for itself when you compare the cost of chemicals and mesh today. Don’t forget to factor in all the lost production time when the screens mysteriously break down half way through a critical production run.
The second rule of thumb is to get ink out of the screen as quickly as possible. After many years of searching for a better solution, I have found that the only thing that seems to work consistently is to integrate this step into the press operator’s breakdown regimen. The press operators should routinely remove as much of the excess ink that they can when the job is complete, and then use a rag and ink remover to clean up whatever is left. The goal is for the press operators to return the screen to the reclaiming area in very much the same condition that they received it from the screenmakers.
I was amazed at how much more economical my press operators became with ink applications once they knew that they would have to clean up the mess. It’s possibly the single most effective way to get them to learn good ink-handling techniques. It also means that less expensive ink is flushed down the drains and into your waste-treatment bills.
The main gripe your operators will have is that the extra step will slow down production. Remind them that production doesn’t just happen on the press. You should be monitoring your process often enough that you can see whether that’s true within a month of implementing the procedure. I assure you that there will be no significant slowdown. However, if there is a major slowdown, you can always return to the messy method.
Better cleanup on press means that the ink will not have time to un-dergo the chemical changes that make it more difficult to remove during reclaiming and will result in much less ghosting and less use of harsh ghost haze removers. The resulting increase in mesh longevity will pay off because the screens will have a better chance to harden off over time and become much more reliable. You also will spend far less money on restretching expensive mesh.
Now the reclaim team is presented with a much more manageable problem. They won’t get excess ink all over everything, and they can go to work immediately on the most important parts of their job. Speed is very important. The less time that you allow a screen to sit before reclaiming, the easier it will be to remove the ink residue and the emulsion from the mesh and return the screen for reuse. Remove spray cans of screen-mesh openers from your press operators’ hands and replace the cans with ink remover. When ink dries in the screen, carefully apply a little ink remover to the underside of the screen, and then print onto newsprint. It might take a little longer, and it’s obviously less convenient. However, I have noticed that whatever is put in the cans of screen-mesh openers fixes the dyes from the ink into the mesh, resulting in the need to dehaze every time the screens are used. Try it, and see if I’m not right.
Correct exposure is another major problem I’ve seen. I mentioned in my last column that one of the most obvious problems resulting from underexposure is that the emulsion will not wash out properly. This problem continues into the reclaiming booth. Remember, your emulsion remover is formulated to work on a substance that has been transformed by the application of intense UV light into something that is quite different chemically from the original. The emulsion remover is formulated to remove the chemically changed emulsion, and it has little effect on the underexposed version. If you don’t allow the chemical reaction to happen, then you might as well blow it out with your pressure washer and forget about the emulsion remover because it will give you the same result.
If you find that there is emulsion left in the mesh after it is reclaimed, then it is almost certainly due to underexposure and not because the chemicals have mysteriously stopped working. Perform an exposure test immediately to make sure. Also, remember that once emulsion residue is left in the mesh after reclaiming, it will become permanent the next time you put it in front of an exposure light, and then it will be impossible to remove. My feeling is that the screen is now unusable and should be completely remade with new mesh.
The final key ingredient to a successful reclaiming process involves our good friend, the pressure washer. If you bought your pressure washer on sale a few months ago at the home-improvement store, then you made the most common, and often the most damaging, mistake in the reclaim area. Use an industrial-strength pressure washer engineered to provide years of service eight hours a day, five days a week. The washers sold at hardware stores will hold pressure for perhaps a month, at the most. After a month, you might as well use a garden hose with your finger held over the nozzle. You don’t shop for presses in the discount aisles at Wal-Mart, nor should you buy your pressure washer there.
Ask your long-suffering rep to recommend a good washer. Then buy it. Not doing this is yet another false economy that will ultimately result in more mesh used and even more production time lost reshooting screens that don’t perform the way they should. Make sure that your maintenance staff has spare rubber seals and bearings on hand at all times. These parts will need to be replaced regularly to keep the pressure washer working properly.
Rethinking the reclaiming process
We’ve learned that the reclaiming process is not so easy after all. There are several other points I want to touch on, but they will have to wait for another column. I must, however, acknowledge the often-overlooked employees that are called upon to do the reclaiming job. Let’s face it, it’s not the most glamorous job in the print shop, but it is one of the most crucial jobs. If one of your employees does a great job in the washout booth, then take a moment to tell him or her how much you appreciate the job they perform. It’s a dirty job, but someone’s got to do it, and it’s up to the rest of us to make sure that it’s possible for our employees to do it well.
Gordon Roberts has a history in screen-printing production management that spans more than 25 years. He has held supervisory positions in shops that represent a broad spectrum of application areas and markets, including printed electronics, apparel, signage, and retail graphics. Roberts has presented training courses on the basics of screen-printing production and on shop management for the Screentech Institute and is presently a consultant for the screen industry. He can be reached at [email protected]
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