Putting Your Reclaiming Tools to Work: Reclaiming Screens to Maximize Your Profits (Part 2)
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Supply 55 - Guardian Laminators, BannerPRO Hemming System, Eco-Solvent Ink, ReelPRO take-up system


Putting Your Reclaiming Tools to Work: Reclaiming Screens to Maximize Your Profits (Part 2)

Reclaiming your screens should take less time thus increasing productivity and your screens should last longer, decreasing expenses. These two factors can make a big impact on your bottom line.

By Bill Stephens

The reclaiming process can be broken down into three steps, according to the type of material you are trying to remove from the screen:

  • Cleaning up the leftover ink
  • Removing the stencil
  • Dealing with haze or ghost images.
Not every screen will need to go through all three steps of the process.

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  • Cleaning up ink
    Ink that has dried in the screen is a chief source of reclaiming problems, so when using air-dry inks you should start your clean-up as soon as possible after the end of the print run. The first part of the job is to scoop up most of the ink. Every printer has his own favorite tool for this purpose: small squares of plastic, palette knives, spreaders from a restaurant supply house. One popular method uses two small cards, one held in each hand. The ink is trapped between the cards and lifted out of the screen. The small plastic squeegees used for applying cut vinyl sign materials make excellent ink lifters, but any reasonably rigid material will work as long as it is impervious to the solvent in the ink and doesn't have rough edges that can damage mesh.

    If the ink you scoop out of the screen appears to be free of dirt and debris, it can safely be returned to the original can. Otherwise, you are better off discarding it. The last thing you want is to contaminate your ink supply with foreign dirt and gunk.

    If you decide to discard the ink, be careful how you dispose of it. Simply dumping it into a garbage bag may seem like the easiest solution, but some inks may contain ingredients that are unwelcome in your local landfill. Be aware of the environmental regulations that govern the disposal of such substances.

    TIP: Should this screen be reclaimed? As you go through the steps of reclaiming a screen, more and more of the mesh will be revealed. Get in the habit of checking the mesh for broken threads, severely abraded areas, and significant loss of tension. There is no point to trying to reclaim a screen that is better off being re-stretched.
    Final clean-up
    The second part of ink clean-up involves getting rid of the rest of the ink. You need two tools for this job: absorbent material (rags or paper toweling) and a screen wash or wash-up containing a solvent capable of breaking down the specific type of ink youíve been using.

    Although the tools are simple, getting the right ones is important. For example, industrial-grade paper products made especially for press clean-ups, while more expensive, are tougher and far more absorbent than ordinary paper towels. In the end, youíll use less of them and your clean-ups will go faster.

    A more critical choice is the wash-up you select. The first thing is to be sure to use a product specifically sold as a screen wash or wash-up. Wash-ups not only contain a solvent that attacks the ink, but chemicals designed to break the ink down and neutralize its adhesive properties. Donít try to use thinner in place of a wash-up. Thinners, like wash-ups, contain solvent, but they lack the emulsifying agents needed to break down the ink. As a result, they merely extend the ink without helping to lift it out of the screen. In fact, the ink may become thin enough to form a transparent haze but it will still be there. Your ink supplier should be able to suggest an appropriate wash-up for the kind of ink you're using.

    Some wash-ups and thinners contain volatile organic compounds (VOCs). When using them, be sure to work in a well-ventilated area and wear protective equipment. You should also be aware that health and safety and environmental regulations may apply to the storage and disposal of absorbent materials saturated with ink and solvents.

    TIP: Protect yourself anytime you are going to be working with reclaiming chemicals. You should be wearing protective gear. Protecting eyes and hands is especially important.
    Reclaim or inventory?
    Unless you are going to be reprinting this particular job in the very near future, it makes sense to reclaim the screen as soon as your print run is finished. If you keep the positive on file, you can simply shoot a new screen whenever the job comes up. Another argument in favor of de-coating a screen promptly is that the longer a stencil remains in the screen the more difficult it can be to remove. On the other hand, when you reprint a job on a regular basis, it can save time and money if you simply inventory the screen. In that case, your ink clean-up has to be especially careful.

    Removing the stencil
    Stencil removers come in the form of liquids, gels, or powders. The powdered types have to be mixed with water before use, and so can be considered to belong to the liquid category. The problem with liquid stencil removers is that they tend to run off the screen. Often they end up in the bottom of the wash tank before they get a chance to attack the stencil. This problem becomes exaggerated when screens are leaned against the back wall of the wash tank at a steep angle.

    One solution is to use a pump spray or a squeeze bottle to apply the stencil remover a little at a time. A long-handled brush also comes in handy for catching the stencil remover as it runs down the screen and working it into the emulsion.

    Gel-type stencil removers can be spread directly onto the screen with a large palette knife. Again, a long-handled brush can be a great help. Many printers prefer using gels because they do a better job of staying on the screen.

    There are probably hundreds of different stencil removers on the market. Some break down the stencil at once, others have to be left on the screen for a period of time. Be sure to follow the instructions for using your stencil remover. A botched reclaiming attempt can result in a stencil that's permanently locked into the mesh.

    TIP: Be aware of environmental issues. ďDrain safeĒ reclaiming chemicals may no longer be acceptable in your local sewer system once they become adulterated with certain types of ink. Check with local environmental authorities. Your wash tank may have to be connected to a water filtration device or recirculation system.
    Using a pressure washer
    Virtually no stencil remover will give good results without a pressure washer to blast away the loosened emulsion. The screen should be positioned in the wash tank with the top edge leaned against the back wall at an angle that provides solid support. It has to be able to stand up to the blast of the pressure washer without being knocked over.

    Be sure the print side of the screen is facing you. A high-pressure spray directed at the squeegee side of the screen can hit the inside edges of the frame and ricochet right back at you. The point where the mesh meets the inside edge of the frame is also one of the most vulnerable points on your screen, really the last place that ought to be hit with a high-pressure jet of water.

    On most pressure washers both the power and the width of the spray can be adjusted. You don't want to concentrate a lot of power in a small area so a fairly broad spray works best. Sometimes it's hard to remember how the spray was adjusted the last time the pressure washer was used, so get into the habit of aiming the wand away from the screen when you pull the trigger. A very narrow spray delivered at a full power can blast right through fine meshes.

    Once all traces of the stencil have been removed, the screen still needs to be degreased before it can be dried and recoated with new emulsion. Degreasing removes oil or contaminants that may have come into contact with the mesh during the reclaiming process. Even a handprint can deposit enough oil to interfere with the new stencil's ability to adhere to the screen, so be careful not to touch the screen after you degrease it.

    TIP: The way water runs down the mesh can tell if a screen needs to be degreased or not. If the water forms beads or rivulets, the screen needs to be degreased. If it runs down the mesh in an unbroken sheet, the screen is ready for the drying cabinet.
    Dehazing is a sometime thing
    Most screens are ready for recoating at this stage, but sometimes screens will have to undergo a further step in the reclaiming process called dehazing. This additional step removes haze or ghost images left behind in the screen once the stencil has been removed. These hangers-on tend to faintly outline the open areas of previous stencils, hence the name ghosts. They are the result of ink residue trapped in the mesh, often in the knuckles of the mesh, those points where threads overlap.

    Dehazing is not something you do automatically every time a screen is reclaimed. In fact, it probably isnít necessary unless the ghosts have become so prominent they are likely to interfere with exposing a new stencil. A good reason for skipping the dehazing step if you can is that dehazers tend to contain harsh caustics, and the fewer times a screen comes into contact with them the longer itís likely to last. Some dehazers, if you leave them on the screen too long, can eat their way right through your mesh. When using such powerful chemicals pay particular attention to the amount of time you allow them to remain on the screen, and be sure to wear eye protection and protective clothing.

    The best way to avoid having to dehaze your screens is to prevent ghosts from forming in the first place. Since ghosts are formed by ink, doing a good job of ink clean-up can help keep them away. But even that may not be enough to prevent your screens from becoming haunted if you are printing with certain types of ink, especially those containing dark pigments.

    After dehazing a screen, itís usually not necessary to degrease it. Most dehazers do an excellent job of removing oils from the mesh. Just be sure to rinse the screen well afterwards. You donít want any traces of dehazer left behind.

    Reclaiming problems
    Most reclaiming problems can be avoided by following a few simple rules:

    • Make sure you are in compliance with all environmental regulations.
      Environmental regulations differ widely from region to region, and violations can carry stiff penalties. Know and obey the rules in your area. Making sure your shop complies when you first set it up can be a lot cheaper than trying to retrofit it later.

    • Buy the best materials and equipment you can afford.
      Donít try to cut corners. Trying to reclaim screens with chemicals never intended for the purpose can ruin mesh and cost you time and money. Buy your reclaiming products from a reputable screen printing supplier, and donít try to skimp on essential equipment like a good pressure washer.

    • Follow instructions.
      Not even the best reclaiming chemicals and equipment can do a good job when used improperly. This seems so obvious that it hardly seems necessary to point it out. Still every year many screens are ruined by a simple failure to do the obvious.

    Trouble-shooting tips
    The longer a stencil remains in a screen the harder the emulsion is likely to become. Get in the habit of reclaiming your screens as soon as you are finished with them. Emulsions can also become excessively hardened through contact with certain strong solvents. If your exposures are bang on and youíre still running into reclaiming problems, try switching to a different wash-up or screen-opener.

    Many reclaiming problems result from mistakes made earlier, during the stencil-making process. Chief among these is underexposing the emulsion. Underexposed emulsion can be virtually locked to the threads of the mesh and may resist all efforts to reclaim it. The solution is to buy and learn how to use an exposure calculator.

    Sometimes stubborn bits of stencil hang on despite your best efforts. Try reapplying the stencil remover or dehazer to that spot. Wait a few minutes and hit it with your pressure washer. Adjust the nozzle to deliver a more finely focused spray. Remember that as the water jet becomes narrower its power increases. Donít let it stay aimed at one small area. Keep it moving.

    Although, we've talked mostly about direct emulsions, the reclaiming process for films is similar. In fact, films can be easier to reclaim. Just remember that indirect films are gelatin-based and require the use of special stencil removers.

    With these tips in mind, reclaiming your screens should take less time and your screens should last longer, two factors that can make a big impact on your bottom line.

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