We’re talking about plastisol's propensity to leave a trail on our textiles.

Screen Print Production

Joe Clarke has spent the past 47 years in the lab and in the engineering department, in pre-press and on-press, as an R&D / technical researcher and as a manager of screen print production. Clarke has held executive positions as President of M&R Printing Equipment and as Vice-President at Wilflex [Poly One]. He has been granted a growing number of print-related patents, including one for High-Shear printing with Smilin'Jack - he is a member of the ASDPT, is an Associate Editor for NBM and an SGIA Fellow.

Clarke has presented hundreds of technical papers, written a couple books and published over 600 technical / management articles for which he has been awarded five Swormstedts; the international standard for excellence in technical writing.

Currently Joe Clarke is the President of CPR, a Chicago-based corporation which manufactures Synergy Inks including NexGen; environmentally & financially responsible T-Shirt inks. For more information on CPR, visit http://www.cprknowsjack.com/.

The paramount value of a plastisol is the fact it never dries in the screen… unless we’re talking about its propensity to leave a trail on our textiles. I realize that, if we put an extraneous spot on a shirt, we’ll need to remove it before we ship. But suppose, rather than looking at the cost of spotting fluid, the delays, short shipments, the residual rings or even those spots that slipped through, what if we look at how not to put so many spots on the shirts in the first place?

A matrix of mess

There are a plethora of causes of spots—not the least of which are those reactive managers who ration out the spotting fluid and the user-friendly hand cleaner thinking they are teaching the staff a lesson in frugality. Equally deluded are those who purchase latex gloves for the press operators; evidence shows they have the cleanest hands and the messiest presses! Production mavens who won’t put a second person on a manual or third person on an automatic press or the boss who buys masking tape and would never spend the money on an ink knife—these too are sponsors of spots.

Even the most brilliant of production managers can miss a few spot-saving techniques. Keep the shop clean to keep both prints and your reputation spotless. (All images courtesy TRUST Printshop)

When going to press, if the screen guy penalizes the press guy by “ganging-up” multiple images, the boss should grind this foolishness to a halt. Other issues include single-axis squeegee blades and metal flood-bars which erode stencils and rip screens, ink pails that haven’t been clean since the UPS girl left, and wooden squeegee handles. But the all-time favorite is the under-exposed stencil… followed by micro-spots which only our customers can find.

The quality that each image deserves is the minimum standard at TRUST Printshop. They select the best raw materials they can find in order to build an integrated printing system. Accordingly, they have less downtime, fewer false starts, less variance and far fewer spots.

Managers’ missteps

My best advice here is to suggest we remember; “only a fool fights in a burning house”—time is our enemy, not the cost of spotting fluid and hand cleaner. If you are hiding or rationing any of the cleaners, you might want to consider the value of a minute of time in your shop and then reconsider the daily scavenger hunt.

It looks like they’re playing surgeons on TV when I see the press operators with those powdered latex gloves, then I glance at the press and realize they are anywhere but in a hospital-clean environment. Latex allows the operator to perform virtually any task while keeping his or her hands clean. Therefore they blithely get ink on their gloves and go right back to work, gloves and all—ink gets everywhere. Get rid of the latex and upgrade to a longer lasting, more bulky glove so they must be removed after clean-up…spend the savings on more hand cleaner.

Staffing, or, more precisely, under-staffing, leads to more mess and scurrilous spots. If you think you can trust person “A” to be fooling with the press and not get ink on their hands, you’d better be embroidering. But if you are, in fact, screen printing, add person “B” to assist on a manual press and person “C” to assist on an auto. The attendants can deal with the ink but not the shirts… production and profits, up; spots and spray-outs, down.

Screens and spots

In this category, the spotting issue is more related to procedure rather than purchasing. So let’s shift gears and try to put more spots on the shirts....

First thing we’d do is to gang-up more images on a screen, so at least one image (maybe more) must be temporarily cordoned off. A manual press costs a company about $1 per minute, an auto runs at about $3 per minute while the cost of a reprocessing a screen costs between $4 (manual) and $7 (auto).

This means that, if the temporary cordoning fails on press and you only lose a few minutes of press-time, then the savings (even if you don’t charge for screens) has been perceived but not real.

Doesn’t it seem we should get a roll of free masking-tape with every gallon of spotting fluid? After all it is so cheap, and the solvent (or plasticizer) in the ink melts the adhesive on the paper tape and turns our multi-layered barricade into seepage central.

Plus, if you’ve never experienced a day of “de-taping”—a term, no doubt, coined by the spotting fluid sales person—do it just for a day. This stuff is nearly impossible to peel intact from any surface. Remember time being our only enemy?

Haze remover is the subtle pre-cursor of screen blow-outs on press. It is necessary because we’ve chosen to “save more money” on the right wash-up. Our ink degradant leaves haze (particularly with blues, blacks and whites) so we hit the screen with some de-haze to eat up anything in its way (including mesh).

Dollars and sense

Our screen maker costs us about $0.25 a minute—a number to remember next time he tries to save himself time at the expense of downtime on press (at $60 to $180 per hour). If he wanted to cause pinholes, he would start with the lowest solids emulsion available, on a low-volume screen mesh with haze and never do a coat-dry-coat since he doesn’t have time.

Because the screen room is wetter than a water slide, exposure will have to be cut back when the stencil is corrugated. The water will cling to the screen until, via our flash units, it evaporates. The membrane-thin coating shrinks on press and pinholes abound.

Now let’s consider the cost of spotting. A minimum-wage employee costs $7.35 per hour and a $20 gallon of fluid costs $0.04 per ¼-oz. This means, if it takes 30 seconds to spot a shirt, the operator can do about 80 dozen flaws a shift for $0.10 per shirt.

If you only have spots on 10 percent of your total output, it only increases your cost $0.01 per every single shirt you print. But this amount pales in comparison to a few minutes wasted on press.

To spot or not?

We have heard a leopard can’t change his spots, but we can change and put the emphasis on efficiency versus sundries… and the rewards are plentiful. Have your actuary tell you how much an hour of press time really costs. Get high-volume/high-modulus mesh, optimize the coating on both sides of the screen, then save the tape by exposing thoroughly. Get a bi-axial squeegee and a polymer flood-bar and set your off-contact gap where it should be.

If you think you don’t need to “clean house” a bit more often, take your cell phone and shoot a dozen or so photos of your facility in operation. Good chance you’ll be shocked at the mess to which you’ve acclimated. Now you can do something about it.