Not only are there hundreds of shades of black, but industrial inkjet ink manufacturers can control other 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. The ink formulation cure or evaporates after it is applied to the substrate, leaving the pigment bound to 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, inkjet 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.
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.
Coding and Marking Ink
But color isn’t the only quality that black ink manufacturers can control. Ink chemists can also improve decap time, which 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 benefits:
- Less set-up/take-down time for printing equipment
- Less chance of human error from handling inkjet printing equipment
Chemists at Kao Collins created Sigma, a solvent ink for HP Specialty Printing Systems, a decap time of more than 12 hours. This is at least 4 times longer than any thermal inkjet solvent ink on the market.
Is there a “best choice?” for black ink
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 practical options. For example, ceramics 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 an ink that meets the technical specifications.
Color and performance tests allow for small adjustments to a formulation until the black ink is perfected. It’s chemical and technical expertise like this that enables ink manufacturers to find expert solutions to unique inkjet printing needs.