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Four Color Process – CMYK Screen Printing on T-Shirts

May 22, 2019

What is Four Color Process, CMYK printing?

CMYK, also known as Four Color Process, stands for Cyan, Magenta, Yellow and Black. CMYK is a color profile originally designed for printing on white paper.  Cyan, Magenta, Yellow and Black are layered in halftones (various densities of dots of each color) in such a way as to produce a full color image. By layering these colors and varying the densities of the halftones, and allowing a white background to show through as well, a decent spectrum of colors can be achieved. In reality, there is technically a 5th “color” involved with CMYK – a white substrate.

CMYK is known as a subtractive process, meaning that for each additional color used, more light is removed to achieve that color. When using 100% values for each color in CMYK, the result is black. By its nature the color profile for CMYK is limited in comparison to the RGB color profile (what you see on computer screens).  RGB results in a more vibrant and diverse color profile than CMYK.

CMYK can be used in screen printing to create a full color design, although there are more considerations and complexities when screen printing CMYK on fabric than printing CMYK on paper, which will be outlined below.

What is RGB Color and how is it different?

In comparison to CMYK, the RGB color profile uses Red, Green, and Blue, the primary colors from which other colors are created. RGB is almost strictly used for digital graphics, as digital devices (phones, computer monitors, etc.) actually use light to create color.  Rather than blending inks which is the case with CMYK, RGB blends light to create its diverse and vibrant color profile.

RGB is considered an additive process, where adding colors together in varying amounts creates the full color spectrum. When adding all colors on the RGB spectrum the result is white, and the absence of RGB colors is black. The RGB color blending method is not used in screen printing because ink is mixed rather than light.

What about PMS Colors?

PMS stands for Pantone Matching System, and unlike CMYK and RGB where colored inks or colored light are mixed together within a design to create the color profile, PMS colors are created by pre-mixing inks before the design is printed.  This allows for exact color matching and consistency in color profile.  The universal PMS method can translate an RGB color to a PMS value and allows for thousands of pre-mixed ink color variations.  In screen printing, using PMS colors is known as the Spot Color method, and is the most common method for screen printing.

CMYK Screen Printing Considerations

Partly due to the differences in color profiles as outlined above, there are definite considerations before choosing the CMYK method for screen printing:

  • Slight variations of print color across garments is unavoidable.
  • Exact color match is not a guarantee. PMS match is not possible.
  • Digital mockups can only approximate the finished CMYK product, as the colors on a monitor are using RGB rather than the more limited CMYK.
  • CMYK does not result in neon or very bright colors. Because it’s a mixture of dots on a non-glossy fabric, it’s not possible to achieve as vibrant of a color result.  If bright or neon colors are important in a design, Spot Color (with Weiskamp standard inks or custom mixed PMS inks) is the recommended method.
  • CMYK is designed to be printed on white. If printing on a dark shirt, the CMYK colors are printed on top of a white ink underbase, which results in a thicker print than on a white shirt. Even though this method on a dark shirt can be done, we would not recommend it for every design. 
  • After CMYK screen printed shirts are washed, the design may lighten up no more than 10%.

Why does the print consistency vary across garments?

For large print runs, the ink consistency may change as it is worked by the squeegee in the screens. This can result in slight color shifts across the print run, often tending toward a darker result near the end of a large print run.

The combination of the CMYK inks are not as predictable on a fabric substrate. CMYK inks are more transparent than spot color inks, so the saturation of the ink can potentially vary across fabrics. Even t-shirts of the same brand may have a variation in thickness, as most shirts are made all over the world. Size smalls might be made in Honduras, and size large might be made in Indonesia. The flexibility and thickness of the fabric is not as uniform as paper, and can introduce variations across the print. The thickness, fabric type, and weave of the shirt can affect the saturation of the ink, which can result in shade variation.

Why is an exact color match not guaranteed?

Closeup of a CMYK screen print

The way CMYK inks are layered to achieve the full color spectrum on the fabric is more art than science, and often requires trial and error to produce the correct shades. Rather than mixing the inks ahead of time to achieve an exact color match like with the Spot Color method, the inks are “mixed” as dot percentages of each color as separate layers on the shirt.  There are also additives in the ink to help achieve fine detail and photo realism, and that may interact with the fabric and affect the color outcome.

As we discussed earlier, the CMYK color gambut is decent, but not all colors you see with RGB (or on a computer screen) can be produced with printed inks. A full color design though is definitely possible, and can produce beautiful results.

Is CMYK the right choice for your design?

Original artwork next to a CMYK screen print on a t-shirt.

Now that we’ve discussed the limitations of CMYK, there are many scenarios where CMYK is a great choice. CMYK allows for a full color design with fewer screens than spot color, making it a more affordable choice for many designs. CMYK can also produce very fine detail, shading, and photo realistic prints that often cannot be achieved through the Spot Color method. A CMYK print also has a very soft hand since the inks aren’t as thick and are more transparent. The photo on the left is original artwork next to a t-shirt screen printed with the CMYK process. 

Design types that would be a good fit for CMYK can include:

  • Hand drawn full color artwork
  • Artwork that has a lot of color and a lot of gradients
  • Designs where slight color differences adds to the uniqueness of the shirt
  • Distressed designs

CMYK Screen Printing at Weiskamp Screen Printing

We want you to be happy with your shirts, so we take extra steps with CMYK printing to help avoid some of the limitations we’ve discussed.

  • To avoid a color shift due to the ink consistency changing during a print run, we sacrifice the first 12 shirts in a print run to allow for the inks to stabilize in consistency.  
  • CMYK jobs are run on an automatic press only so the pressure of the ink application does not vary across prints. This helps avoid variations in the saturation of the print, which helps maintain color consistency.
  • We require approval in-person (preferred) or from a photograph of the 13th shirt in the print run. This final approval will need to be scheduled ahead of time to accommodate the production team’s schedule and yours.
  • To fulfill these extra steps, a 10% upcharge is added for CMYK printing.  This includes one additional set of screens with adjusted artwork if the in-person print is declined.

Contact us today to see if CMYK is a good fit for your next t-shirt design!