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October 12, 2017

Science of Black Ink

Black ink is everywhere, so it probably comes as no surprise that there are countless formulations for black ink.

Not only are there hundreds of shades of black, but ink manufacturers can control other physical properties of the black ink down to a molecular level. Adhesion, longevity, and decap time all play a role in formulating a black ink specific for the intended application.

Pigment-based black ink

Pigmented black ink starts with a dry, powdered compound created from carbon particles. These pigments are mixed with a liquid (like water or oil) to create the ink. The pigment remains suspended in the liquid. After being applied to a surface, the liquid evaporates (or is cured), leaving the pigment strongly bound to the top of the surface.

Dye-based black ink

Dye-based black inks use colorants that are fully dissolved into a liquid (like water or oil). Most black dye-based inks include a combination of black dye and additional cyan, magenta, and yellow (CMYK) dyes to create a rich black. When dye-based ink is applied to a surface, the fully dissolved liquid soaks into the surface. Dryers then cure the ink to prevent it from smearing.

How can there be shades of black?

Black ink formulations are almost infinite. For a specific application, ink chemists may choose to create a fully pigment-based ink or a fully dye-based ink, or they may combine pigments and dyes. One common scenario involves chemists taking a pigment-based ink designed for durability and maximum adhesion and adding black dye to improve the brilliance of the color.

Abstract black ink image

Additionally, ink chemists can choose from multiple black inks and dyes, each of which can have slightly different hues. Many standard dye-based inks often look blue once printed, and many pigment-based inks can appear somewhat brown. By carefully choosing to use specific dyes or pigments, ink manufacturers can meet precise color specifications.

But color isn’t the only quality that black ink manufacturers can control. Ink chemists can also improve an ink’s decap time. The decap time refers to how long a printer can sit inactively and still resume printing without any adverse effects on the machinery or print quality.

Black inks with longer decap times offer two unique value propositions: (1) less set-up/take-down time for printing equipment and (2) less chance of human error from handling inkjet printing equipment

In some cases, ink manufacturers have been known to formulate inks with decap times of 16 hours!

Is there a “best choice?”

Both pigment-based and dye-based black inks have advantages. In general, dye-based inks create a more brilliant color than pigmented black inks and are less expensive, but they tend to degrade or fade over time.

Pigment-based inks have superior binding ability, but their color can look a little lighter than a dye-based black. Pigment inks are typically more expensive than dye inks, as well. For specific substrates, pigment-based black inks are the only realistic options. For example, ceramics (a relatively new substrate benefitting from inkjet technology) exclusively rely on pigmented inks because of the adhesive properties.

The steps to creating a black ink

When creating black ink, most ink chemists begin by asking the right questions. The ink manufacturer will want to know precisely on what substrate the ink will be printed, in what environment the final printed piece will exist, and the expected production cycle. Based on the various specifications, the ink chemist will then begin developing a proper ink.

Color and performance tests allow for small tweaks to the formulation until the black ink is perfected. It’s chemical and technical expertise like this that allow ink manufacturers to find expert solutions to unique inkjet printing needs.

Contact Kao Collins to discuss custom inkjet ink formulations.

Kao Collins produces inkjet inks for these printheads: Dimatix, Funai, HP, Kodak, Konica Minolta, Kyocera, Panasonic, Ricoh, SII Printek, and Xaar.

 

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