Digital BW, The Print

Richard Smallfield wrote:
 
> > ... why doesn't Epson  
> > use low-gamut pigments, as manufacturers like Cone do, 
> > to make the K/ LK/LLK inks neutral

Separation of the inks and color instability may be one reason.  See page 4 of http://www.paulroark.com/BW-Info/4K+.pdf

> > - so that when printing BW, we are not balancing  
> > the warm carbon pigment with the less stable high-gamut coloured  
> > pigments that their coloured inks use?

The "neutral" B&W and HP inks are blends of carbon with color that still have the disadvantages -- in a lesser degree -- of the color ink weaknesses. 

My use of the relatively neutral Eboni to make 100% carbon pigment B&W prints is the only pure carbon, relatively neutral approach I'm aware of.  See page 7 of http://www.paulroark.com/BW-Info/Eboni-6.pdf to see just how neutral I can print with even the dilute Eboni with my 7500.

> >I can't see what downside there would be in producing perfectly  
> > neutral black ink, with neutral dilutions. 

If they could do so, they would have.  

The majors can't even follow the Eboni model be cause it will not meet their standards with respect to settlement.  The neutrality comes, in part, from the size of the particle.  The larger the particles, the more neutral they tend to be.  Eboni is still tiny relative to the nozzle. (I fired up the 1800 3MK system the other day, and it had no Eboni clogs after 8 months of non-use.)  However, the Eboni particle is large compared to, for example, the MIS LK, which is warmer and more stable in suspension than the Epson LK, probably because it is ground smaller.  

The 3800 can't match the 7500 with Eboni-6 either, because the 7500 large dot is part of why it can be so neutral.  Warmth of carbon appears to be largely an edge effect.  As the particle or dot become larger, the area and thus image density increases by the square of the radius, whereas the edge -- circumference -- increases linearly.

Dilute carbon is warmer than 100% carbon, probably due to the greater transparency of the dots.



C D Tobie <CDTobie@...> wrote:

> ...HP uses a solution related to this by tuning the color 
> of their gray inks in the ink formulation.  
> This is fine, but very limiting in terms of media; 
> only certain media  will print neutrally with such inks, ...

Actually, I'm rather impressed by how neutral the HP pigs are on lots of media.  HP has done an impressive job of matching the various color and carbon pigments in their brew so that the variance in tone and separation of the color inks in the suspension is relatively minor.  It's not perfect, but the HP R&D capabilities are apparent.  Still, they failed to find a way to make a 100% carbon neutral ink.

> In terms of low gamut color in separate carts, ...
> all the manufacturers have chosen not to offer as a solution.

Which also means that those of us who like to take the road less traveled don't have the low gamut colors available to us.  I've used some watercolor pigments to print with in experimental inksets, but they are not suitable for commercialization, and making them such takes a huge order that a small company is not likely to take the risk on.  If one wants to, I happen to know of a single pigment toner that virtually perfectly offsets the carbon warm.  So, there would be a non-separating, low-gamut toner that would do the job and only take a single channel.  The separate dots don't stand out at all on the paper.

The truth is B&W printing is a side show for the large OEMs.  We're a gnat, but this too is a double edged sword.  I'm very happy that the OEMs can match what I do.

Paul
www.PaulRoark.com