There are two different Piezography systems that are now available. Each uses a different ink system and offers different possibilities.
The latest system released in 2016 is called Piezography Pro and uses only one ink set to produce a million different tones and split tones which are easily set in software. It also features one pass gloss printing and considerably darker dMax.
Piezography K7 first released in 2005 offers five different ink sets that produce a single tone each. It requires two pass gloss printing, but is also compatible with PiezoDN digital negative if a glossy compatible ink set is chosen. You can read more about the Piezography Pro system by clicking here, and read more about the differences between Piezography Pro and Piezography K7 ink sets by clicking here.