How to Assess Correct Color Order

When working on production screen print jobs, follow this advice to achieve bright, quality images on finished prints May 02, 2011
By James Ortolani, Contributing Writer

Shown here is an example of first printing a white underbase, flashing and then printing the subsequent colors wet-on-wet on top of the underbase.

Editor’s Note: The information in this article is geared mainly toward color order for spot-color jobs, which allow the operator to swap color order on press as needed. But when a job calls for simulated-process color work, a pre-determined color order may need to be followed. There are some color separations (such as stock art designs separated for doing simulated-process work) that do need to stick with a preset color order to make the design print properly. You can tweak the ink colors, but typically not the color order. (However, for the simulated process parrot design used in this article, we did print the yellow last and it made the design look much better. Screen printing is all about exceptions to the rules!)

If you’ve ever watched watching an automatic screen printing press churn out 50 to 60 dozen eight-color garments an hour, it looks as if the machine does all the work. But there is more involved with setting up a production job than meets the eye. It all starts with the image, color separations and pre-determining the print order for the colors.

First, it is important that the artwork is butt-to-butt color separated with no overlapping. Color separations that overlap lose the flexibility to move a color (screen) from the front of a print run toward the end of the print order if adjustments need to be made. And although ink manufacturers promote their inks for wet-on-wet printing, it would be more accurate to call these inks “wet-next-to-wet,” since it is not recommended to literally print wet ink on top of wet ink — especially when printing spot colors.

Also, when setting up a job on the press, it is important to experiment with the color order to achieve best results. The most common color order for printing on white garments is to print light to dark. But rules in screen printing as they relate to color order are made to be broken because of the uniqueness of each image to be printed.

Making the artwork print correctly may require changing the print order that the artist originally had in mind. Here’s an example: To tone down a certain color, it is possible to slightly diminish its brightness by moving it to the front of the print order. This is achieved because the subsequent screens that come in contact with this color will pick up on the backs of the next screens. And to make a color brighter, simply move that color to the end of the print order to reduce the ink pickup factor.

When printing on dark garments, the aforementioned color order is reversed. So typically you would start by printing the underbase color, followed by purple, blue, green, red, orange and yellow, finishing with a white highlight. When printing wet-on-wet, the colors are picked up on the backs of the screens. To reduce this factor, lighter ink colors, such as red, orange and yellow, are printed toward the end of the print order. For instance, if the color yellow is printed first, multiple screens would come in contact with the yellow, picking up color and reducing the brightness on the garment.

Special-effects (SFX) inks, such as metallics, puffs or suede inks, should be printed last or next-to-last in the print order to avoid multiple screens from coming in contact with the wet ink deposit of the previous colors printed. Unfortunately, you can’t print every color last when printing with multiple special-effects inks. So it may be necessary to flash one SFX ink to maintain the optimal amount of ink coverage on the garment before the next SFX ink is printed. Again, always try to position these SFX inks at the end of the print order for best results.

Another consideration when determining the color order of a given job is to assess the percentage of image area to be printed. This means that if a color is a small component in the design, it should be positioned at the beginning of the print order. But if the color to be printed represents a large area of ink coverage, this screen is best to be positioned at the end of the print order to reduce ink buildup on the backs of the other screens that will be printed. Wouldn’t it be nice to print everything last?

Flashing & Fibrillation
In a perfect world, artwork would be engineered to be printed wet-on-wet; this is possible when designing art to be printed on light-colored garments. But in the case of printing on dark garments, it is next to impossible to get the desired results without flashing certain colors.

When printing a dark garment, the first underbase color (usually white) typically is printed, flashed and allowed to cool before the next colors are printed on top. Many automatic presses have 12 stations to allow for this critical cool down at an open print station before the next color is printed.

And if all goes well, it is possible only to flash once at the beginning of the print order and then all of the following colors can be printed wet-on-wet directly on top of the underbase color. But the colors printed in the middle of the print order often will begin to diminish in brightness due to the ink pickup value. So to reduce this problem, it may be necessary to add a second flash station somewhere in the middle of the print run to help maintain color brightness.

Color order shouldn’t be the only consideration when setting up the press for a production run. Factors such as controlling downward squeegee pressure also play a major role in achieving the brightest print on dark garments.

Excessive squeegee pressure can drive the ink through the garment. This exposes the garment’s surface fibers that protrude through the ink deposit, making the ink appear washed out. This problem is called fibrillation. By using high-tensioned screens and backing off on the squeegee pressure, the ink is printed onto the surface of the garment, yielding the best ink coverage and opacity.

If ink residue can be seen on the shirt board after a garment is printed and unloaded from the press, then too much squeegee pressure is being used. Ease up on the pressure — the goal is to print onto the surface of the garment, not to drive ink all the way through to the shirt board.

Don't Forget Your Manual
Challenging designs and some special-effects inks may be better suited to print on a manual screen printing press instead of an automatic due to the versatility it provides. Manual printing allows you to make many on-press adjustments as you print, whereas the automatic press operates within more rigid confines.

Using a manual press, the operator can print a color twice (or not), flash whenever necessary or change the color order on the fly. This style of printing is not as feasible with an automatic screen printing press, where print-and-flash sequences are preset. Automatic presses are the backbone of our industry for production but — depending on the order size — there are some designs that are better suited to be printed on a manual press.

Considering the special care needed to print them, some special-effects inks like shimmer, puff and high-density inks are good candidates to be printed on the manual press. Glitter is another good example of an ink that many shops print manually since multiple squeegee passes may be required as the ink’s flow characteristics and glitter load change. Obviously, you can print all these ink types on an automatic, but the manual press is a great tool for those out-of-the-ordinary jobs.

Finally, here are some off-contact and screen mesh considerations. Garments are screen printed with the screens set 1⁄16 or less off-contact from the surface of the garment. The downward pressure from the force of the squeegee allows the screen to touch the garment only during the print stroke sequence and then the screen “snaps off” the surface of the garment right behind the squeegee stroke. Increasing this off-contact distance (between the garment and the screen) increases the ink deposit, and reducing the off-contact distance reduces the amount of ink that is printed onto the surface of the garment. Controlling your ink deposit with your off-contact setting is the key to reducing the ink pickup on the backs of screens.

Our industry has come a long way in the past decade by moving to higher mesh counts on multicolor jobs to help control ink deposits and to ensure a soft-hand feel to the finished print. Finding the right balance between all of the factors listed above will help you streamline your production flow and yield brighter, quality images moving forward.

James Ortolani has more than 25 years of experience in the decorated apparel industry, specializing in hands-on direct screen printing and heat transfer production. He has worked for various industry suppliers and currently serves as national sales manager for Hix Corp., Pittsburg, Kan. For more information or to comment on this article, e-mail James at jortolani@hixcorp.com.



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