how to set an HP printer in black+white mode

[Jon Grant]

Hi Mitch,

Thanks for the tip.

I didn't have that option, so I reconfigured the printer as using the
alternate driver "HP DeskJet 930C - CUPS+Gutenprint v5.0.0". which has a
"Color Model" option! I set it to Greyscale instead of RGB, and it seems
to work.

Yeah, unfortunately I need to leave the duff CMYK cartridge in place.
presumably HP doesnt want to support a product which doesn't have an
up-to-date full and official HP CMYK cartridge!

Thanks again for the tip!
Jon