Digital BW, The Print

> I have a 4000 and the clogging can be intensely irritating. ...

That machine does have a reputation for clogging.  I wonder what Epson did differently on it that caused that problem.  The frequency of complaints is like a throw-back to the 1280 days.

I have not used a K7 inkset, but with respect to the MIS offerings and the inks I've used, the matte-only Eboni-6 and my Carbon-6 midtones appear to be clog free.  The Eboni in my 7500 will occassionally need a cleaning cycle, but I don't think I've even had a clog with an ink made with the C6 base, which has a high glycerol content and no binder in it.  (I'm excluding from this generalization problems I've had with carts for the 1800 & 220.)  The HP-C6 dilutions also appear to be clog free, although the 1400 is the only printer I've had those in for an extended period.

So, if I had a 4000, I'd use some combination that used the dilute Eboni (needs agitation) and C6-diluted HP Z3100 PK (more stable than HP's own dilutions).  C6-diluted MIS PK is a warmer version of the 100% carbon approach that is also more stable in suspension than Epson's LK, according to my centrifuge tests.

The C6-dilution approach I'm referring to is described at 
http://www.paulroark.com/BW-Info/Ink-Mixing.pdf

Paul
www.PaulRoark.com