Digital BW, The Print

says 18 picoliter droplet for the black head, 4 picoliter droplet for the color nozzles.

I have used the HP Z3200 Vivera pigment MK (matte black) ink in a similar 88 black head of the HP K5400 OfficeJet. But 9 picoliter droplet on the black side, possibly 6 picoliter on yellow. Cyan and magenta are 6 picoliter.

In the cyan channel of that printer the Z3200 Vivera pigment PK (photo black), on the magenta channel a 1/3 dilution of the PK, on the yellow channel a 1/9 dilution of the PK. Tweaked the channels with Photoshop ACV curves later on packed in an ICC profile together with a linearisation curve (Paul Roark + Roy to thank for these features). Matte (4ink), Gloss (3ink). Printing from Qimage Ultimate + Windows driver.

Ink medium to dilute the PK: http://www.octopus-office.de/en/shop/details/c/printer-ink-for-kodak-10-c/p/ocp-gloss-optimizer-for-kodak-10-c/

Both inks and ink medium are intended for the thermal heads that the mentioned HP models have.

I have done this experiment on the desktop model to see whether it would be possible on a 4 to 6 channel Designjet later on. I am quite convinced it would be possible. Main problem is the bigger droplet size of Designjets (other than the Z versions and the 130, 90 etc serie that have droplets 4-6 picoliter).