Digital BW, The Print

Joost,

>... I had not realized the "split-tone behaviour" HP inks.

It is typical of cooled carbon inks.  It takes more cool color in the highlights than the shadows to have a level tonal response.

> Wrt to warm toner: you suggest to consider a single EZ-warm. 
> What's the density compared to MIS LK and LLK? 

EZ carbon is 75% of LK.

>I happen to have a stock of both LK and LLK. I could easily mix them to create an intermediate density. 

> For future use I could slightly dilute LK.

With glop to keep it as glossy as before, although I'm not sure what the small amount of generic base would do to the glossiness of the LK.

 
> Based on your feedback I'm tempted to go for
> 
> MK
> PK 100%
> LPK 50%

One person reported excess foaming in a 50% mix, but his last analysis of the problem indicated it was probably due to an incompatibility with the Piezo ink that was previously in the cart.  I did not have the excess foaming in the 50% mix I tested. 

> LLPK 25%
> LLLPK 12%
> LLLLPK 6%
> warm toner (LK / LLK mix)
> glop
> 
> I don't full grasp your reasoning wrt the distribution of the dilutions over the ink slots to achieve Epson driver compatibility. How would you distribute the set above?

Aside from the light inks being in the light ink spots and about 1/3 the density of the dark inks they'll cross over to, the main issue with k3 printers is the LK position density.  If it is too low relative to the C and M, you'll get a posterization in the shadows.  The HP PK in the LK spot would avoid this problem, but it would also stop you from being able to use the Epson driver for glossy printing.  I'm not sure if the 50% HP PK in the LK spot will be enough to avoid posterization.  So, there is a trade off here.  Since you are using QTR for most printing, it may be that just keeping the Epson driver matte paper compatible is the best you can do.

You might try this:
K = Eboni
LK = HP PK
LLK = 25% HP PK

C = 50% HP PK 
LC = 12% HP PK

M = EZ
LM = 6% HP PK

Y = glop