Digital BW, The Print

In my experience, I've simply found that printers charge by the number 
of colors running.  It's more work to register the dot from 2 printers, 
and of course 2 uses more ink.  Plus there is the need for a second 
plate.  It may still run on a 4 or 6 color press, but the other 
printers will be turned off.  The other option for them is to run twice 
on a single color press, but this doubles the time required, and that's 
another issue/problem.

As far as gettting better blacks with Piezo, it's unlikely double 
passes of solid black will add much to the DMax, since a nearly solid 
blanket of carbon is being laid down on just a single pass, and the 
DMax can't exceed the carbon's reflectivity/absorbtion.  Adding more 
won't contribute much, I don't think.  In the printing business, they 
are dealing with inks as opposed to pigment, and inks are transparent.  
Therefore getting thicker layers on the sheet produces visibly darker 
tones.

Phil
http://philbard.com

> 
> Every technology seems to have it's own vocabulary which is rapidly 
> changing in meaning as technology increases. I also thought it 
> referred to a way to increase black with a single plate and pass 
> through the press. It's the plates and passes that control the cost. 
> Maybe you run the same plate twice with different ink loading to 
> punch up the blacks. You pay for the double pass but not the extra 
> plate. Just a thought.
> 
> Martin