Tech Tips

A series of Technical Tips for inks and processes from Zeres.

Coated vs. Uncoated Color

PMS Coated vs. PMS Uncoated

The PMS (Pantone Matching System) contains two very different lines of color references related to substrates. These two lines are referred to as PMS C (coated) and PMS U (uncoated). The C and U refer to the substrate the correlating PMS color chip is intended to be matched and ultimately printed on.

Here are a few examples of both types of substrate:
Coated Liner/Substrate                                           Uncoated Liner/Substrate
Kemi (lite, graph etc…)                                           Mottled
C.I.P (clay impregnated)                                         Bleach
SBS Bleached                                                        Kraft

It is ideal for the customer to choose the appropriate color from either the C or U PMS book based on the substrate.

The main difference between the coated and uncoated substrate is ink hold-out.
Ink hold-out is the ability or inability of the ink to penetrate the substrate. A coated substrate has a much higher ink hold-out than an uncoated substrate. This hold-out allows the ink to sit on top of the substrate and not absorb into the substrate. This gives the color a very dense and/or bright appearance, whereas an uncoated substrate will give the color a less dense and flat/muddy appearance.

Here is an example of the difference in the PMS U and C books using the same color for reference:


As you can see, the PMS U color is less dense, flatter, and appears “dirtier” than the PMS C color on the right. This is due to the C substrate allowing the ink to sit on top of the substrate whereas the U substrate allows the ink to be absorbed.

The difficulty for color matchers and ink suppliers is attempting to match a color intended to represent a C match but then is printed on a U substrate. The uncoated substrate simply does not allow the ink to sit on top of the substrate causing the color to lose its “pop” and density. Along with the loss in density, the uncoated substrate gives the color the appearance of being “dirty” or “muddy”. This is problem when attempting to match a PMS C color chip that is light in color or is “clean/bright” in color.

Here is an example of a light/clean color:


In the above example, the Cool Gray 1 C appears cleaner and crisper. The Cool Gray 1 U appears flatter and takes on more of a yellow tone.

The above samples are a few examples of why it is not best practice to use a C color chip for uncoated substrates. There are also some other factors to consider. One being resistance properties, especially rub (wet or dry). A dense C match requires more dispersion or pigment (color portion of the formula) to reach the strength level. This would take away from the resin (clear material in the formula that helps the ink transfer and bond) portion of the formula which in turn could cause excess rub when handled after printed.

Please take all of the information above into consideration when discussing color with the customer.


(Zeres Inc.  7/17/2013)

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