One of the significant technology that the HP Indigo uses that makes its digital print superior than other digital presses is its liquid ink technology called Electroink.  HP's unique liquid ink has a much finer dot definition than toner based systems and follows the contours and profiles of the paper to produce a litho comparable quality. 

Below are some FAQs about HP's electroink.

What is HP Electroink?

hp ElectroInk is a unique liquid ink that combines the advantages of electronic printing with the qualities of liquid ink. hp ElectroInk contains charged pigmented particles in a liquid carrier, and enables digital printing by electrically controlling the location of these particles.

How does HP ElectroInk support the performance required for high quality, digital color printing?

The small particle size in the liquid carrier enables high resolution, uniform gloss, sharp image edges, and very thin image layers which closely follow the surface topography of the paper resulting in a highly uniform finish.

Do images printed with HP ElectroInk have any degradation of color values?

Images printed with hp ElectroInk were analyzed after a print run of 100,000 impressions, and measured for a
change in color. The analysis found no degradation in color values of the xth print compared to the 1st print