Digital BW, The Print

While waiting for Jon Cone to make his cartridge refill kits available, I've been using Epson 
carts on my R2400.

I ran a test of ABW against the QTR driver using Keith Cooper's B&W image (at 
www.northlight-images.co.uk/digital_black_white.html) printed on EEM.

With ABW, I followed Clayton Jones's suggested workflow, Light tone and -5% ink and 
compared it with QTR using the quad2400 driver.  In both cases I chose Neutral for EEM 
paper.

There is a subtle, but noticeable, difference, with the QTR driver producing a better tonal 
spectrum.

ABW does add a small amount of color, raising a question of long term stability.  But I'm 
guessing that QTR uses only the three blacks and would, therefore, avoid this problem.  Am I 
guessing correctly?

(Of course, I'm aware of stability problems with EEM itself, but that's not at issue here.)

Harry