4 color process screen printed t-shirts - magenta pre-press film variations, Seattle, Portland Oregon

Four Color Process Screen Printing: Challenges and Opportunties

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Dialing in the coloring with four color process screen printing is part software, part artistic judgment.  We recently took a call from a Corvallis, Oregon customer, about 50 miles south of Portland.  The customer needed this logo screen printed onto 100 t-shirts in time for the Washington State Fair, which is held about 50 miles south of Seattle.  BeerHaven Festival Logo Original Art

The lion’s share of the screen print jobs we do are spot printing jobs, which is essentially printing line art onto fabric.  Art like this looks great on a glossy poster.  It is a challenge to do something like this well on fabric.  In fact it requires a type of printing that most screen printing shops cannot or will not do, which is four (4) color process printing.

We LOVE doing four (4) color process screen print jobs because they are challenging!  The original art is usually visually stunning and we always like to showcase our ability to do high quality work.  Four color process is the only true screen printing method of trying to achieve a near photo quality image on a shirt.

So what makes process printing difficult?  With spot printing, which is what most people think of when they think of screen printing, most of the line art that is printed on the shirts is contiguous, or a series of large contiguous areas for each color (i.e., blue goes here, white goes there, etc).  There is a screen for each ink color, and each ink color is matched to the pantones requested by the client.

With process printing, you lose the large contiguous areas of print.  It is more like impressionistic painting, and translucent inks are blended together to form the desired image.  The original art has to go through a color separation process in which we have specialized software attempt to interpret the blends of colors and shading you see in the original art on your screen into four defined colors.  Can you guess what the colors are (hint: dig back to grammar school science)?

The software the takes the original image and separates it into four separate grayscale images, respectively representing our hero colors of cyan, magenta, yellow, and black.

The grayscale images are printed onto sheets of transparent plastic film.  The films are placed atop screens and fixed into a vacuum sealed container, which is then time exposed to very high intensity light in order to “burn” the film image into the screen.  The resulting screens are set onto the automatic press.  The cyan, magenta, yellow, and black inks designed for process printing are applied to the screens.  We hit the Start button, the press spins, the ink is pushed along the screens via industrial squeegees and then flash heated….  Voila!  A perfect blend of cyan, magenta, yellow, and black ink, just like the original art!  Four color process printed tees t-shirts, Seattle, Portland - 1st color match attempt -- failed due to too much red.

“Whoa?!” you exclaim.  “Not quite.  What happened to my scientific pantone color matching?  We spent serious money developing a corporate branding style guide with specific pantones.”

The truth is that the pantone matching process goes right out the window with process printing in favor of old fashioned human judgment by eyeball.  Why?  Think back to the computer doing the color separations — can any software actually “see” an image?  No, it is merely interpeting data points as series of 0’s and 1’s, then plotting those data points into grayscale for the films.

The first attempt clearly had too much red.  It was back to the software to manually dial back the magenta.  Then print another sheet of film, burn a new magenta screen, reset onto the press, add magenta ink, hit Start, and problem is solved!4 color process screen print shop, Seattle, Portland - 2nd color match attempt failed due to not enough red.

“No way!” you shout.  “Where did my browns go?”  The photo here doesn’t do the image true justice, but it looked like teal and pineapple yellow.  We had obviously pared back the magenta too much.

Back to the software, manually adjust the degree of magenta again, print new film, burn a new magenta screen, reset the screen onto the press, add the ink, hit Start again.  The press whirls, the squeegees push ink, the flash heaters cure the ink between the color pressings.

What do you think…?

4-color-process-screen-print-Seattle-Bellevue-PortlandI think we nailed it!  Well, we nailed it as closely as possible considering that we were printing glossy art onto the visually flat medium of cotton fabric.

The featured image at the top of this page shows the three different magenta films we printed over the course of trying to get the colors matched properly.  Can you see how it is a judgment call to try guess how much more or less grayscale will provide the desired result?

The entire process of trying to get the coloring right took about three hours.  Printing a sheet of film takes about twenty-five minutes.  Burning a screen takes about ten minutes.  Setting the screen and ink onto the press takes about ten minutes.  Manipulating the colors in the software to print as lighter or darker on the films takes about 10 minutes.  During that three hours, the automatic press has been set-up and dedicated to this job, but not producing shirts  — not generating income from other jobs.  The good news for both our shop and the customer is that any reprints with future orders will go much easier because we have already dialed in the coloring.

So when a customer asks why there is a hefty fee for color separation on process printing jobs, there are three reasons:

  1. It requires specialized software and technical expertise.
  2. It can be labor intensive in both human and machine terms.
  3. It often involves hours of machine downtime during the color testing process

Doing quality process work means accepting the above.  Many shops will not even take on four color process screen printing jobs, either because they lack the proper equipment or do not want to risk the machine down time.  Bring those process printing jobs on!  We love doing quality work.
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