Mixing ink

Orchestrating the Variables

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/.

Print practitioners are prone to perennial mistakes when outfitting our shops with the tools of the trade. We make decisions based purely on emotion, yet tell ourselves and sales reps we are making fiscally-responsible decisions. Nothing could be further from the truth. 

It has been my experience that not enough shops are spending enough on core components. While many wrestle with the high cost of labor, the cornucopia of competition, the shrinking of profits and shirts, and sleep lost in the unpredictable and inconsistent screen-printing business, others take a look at how to avoid this trap altogether.

How did we get here?

A recent article for Printwear (see May 2010 page 72, go to http://printwearmag.com/articleauthors/joe-clarke, or scan QR code below) illustrated that the cost for all core components (frame, mesh, adhesive, stencil, blade and ink chemistry) for screen printing T-shirts accounts for about 5 percent of total costs. Most professionals treat all of the core components as commodities, not because they are commodities, but because no one has brought to the market an integrated system of core components for high-volume screen-printing on T-shirts. 

Instead, the usual cast of characters includes the wrong mesh that is illogically tensioned, coated the wrong way and then grossly under-exposed. The cheapest ink money can buy is then pushed through that combo with a blade which may as well have been a junkyard retread… and we all wonder why we struggle on (an un-calibrated) press which never seems to have enough flashes. 

How did a group of logical adults and professionals get so far off course?

Here’s a likely scenario: the boss says “don’t use that mesh, it rips too fast” so the screen-room guy finds the highest possible count he can to hold every one of those teeny little lines and dots. It gets stretched with a meter that is completely insensitive to variance in elongation which results in irrevocable loss of any kind of printing or dynamic tension, crimp angles that don’t match because the screen is unstable, and imbalanced mesh openings which compromises image integrity and fluid transfer. 

The screen is typically coated with a single emulsion (never considering the squeegee and substrate sides have opposite requirements), the purchasing department found a deal on blades and the flood-bars are made of sharp rigid metal for metering ink onto or into fragile, elastic polyester. Then, just to be sure the press operator doesn’t have a snow-ball’s chance, we over flash the cheapest ink we can find in case there’s any problem. 

The Good Samaritan

Enter our “trusted advisors”—those loyal, local sales reps that diligently look for the right stuff for our operations. They come in and tell us about the week of sales training they spent on the new fill-in-the-blank and they help set it up to test. But testing doesn’t necessarily go as smoothly as we all hope and at a certain point, the prudent shop owner puts an end to the testing. But is that really prudent? There are so many variables that are difficult to fine-tune; the reason many don’t upgrade core components. Understandable? Sure… but in no way excusable. Better product will improve efficiency and quality no doubt so long as their implementation is orchestrated a little more efficiently. Those who upgrade must realize what each of the core components are meant to do:

The mesh defines the ink deposit but constrains ink volume. The knuckles of the mesh limit the highlight (or line) while the opening limits the shadow (or the space). It must be tensioned for stability and fluid transfer. 

The stencil defines the image’s edge-acuity. It has nearly unlimited resolution and yet it must be designed and applied to regulate the proper ink volume for details. The flood and print blades thin the ink via maximum shear rate (stroke speed) and must then deliver the precise ink volume within the limits of the stencil’s edge-acuity. 

The ink must begin to flow under minimum force, thin to reach a minimum viscosity at the neck of the fabric, wet the shirt (or ink deposit on the shirt), release the mesh without ink sagging but level to a smooth finish. 

The press is the instrument with which we make money. Whatever it takes for you to get to press prepared to print; the investment is likely to be worthwhile. 

Shopping list

So if you are in the market for an integrated system, first dedicate some shop and press time for system characterization and calibration. Diagnose why you are fighting with wet and dry artifacts (see Index 1, right) and begin with a high-volume screen mesh stretched by percentage of elongation. Find an Rz meter and EOM gauge—because you have to calibrate how to coat a screen on your own, keeping in mind that the substrate side of the stencil controls the shape of the image, the squeegee side of the stencil regulates the volume. The ideal blade will run at or near zero degrees with minimum pressure at maximum speed, without distortion even when printing close to the inside of the frame—this is how one matches ink volume to ink height. 

Once you orchestrate these core components you will have a sensible “pump” (screen printing is a hydraulic pumping process). Soon as the pump is ready try out a few different inks, you’ll know the right one… it’ll fit your pump naturally!

The only significant costs in a screen-printing business are those based on time… specifically unproductive time. While it’s important to use the best core components money can buy, it’s equally important to characterize your current system and calibrate for the upgrade. After all, it’s the logical thing to do.

Wet or Dry-There Can Be Only One!

Arguably, nearly all the time invested (or wasted, depending on your perspective) on printing T-shirts is due to an imbalance of ink height and ink volume. And, as Highlander Duncan MacLeod so aptly put it, “there can be only one.” Similarly—albeit less melodramatic—for any given ink height as demanded by the mesh, there is only one ideal volume which should be supplied by the squeegee. 

Supply a bit more and the print will run too “rich” (resulting in wet artifacts). Supply a bit less and the print will run too “lean” (resulting in dry artifacts). Fortunately, wet and dry artifacts cannot coexist in the same time-space continuum.

If fighting wet artifacts… it is, at least in part, due to a lame upper-seal between the blade and mesh and a late lower-seal between the stencil and the substrate. If the blade will permit, reduce its angle (the ideal is zero degrees) so it will meter a more tolerable ink volume and then seal the stencil to the substrate instantly after the ink is transferred. 

Conversely, if dry artifacts underpin your nightmares, it is due to the way you Molly-coddle your ink (we used to call it “pampering one’s plastisol” before we awakened to water-based inks). If you have dry artifacts and you are running at or near vertical, crank the stroke speed to 75 percent of maximum—the “leanness” will go away for good and you will not lose any detail or edge definition.