Digital BW, The Print

Hi all

I've been redoing some QTR curves from 1440 to 2280 dpi lately and re-
encounter an effect I've was not sure it was there actually. My 
measured Dmax seems to vary quite wildy when I measure the same step 
wedges on different moments, also after drying properly.

Currently, I'm trying different ink limits/black boost/overlap QTR 
settings. But the differences between the settings seem to disappear 
in the noise of my measurements.

My setup: QTR/Windows/Epson 2200/UT3D/Enhanced Matte/Eye-One.

Most of the time I measure L*/Dmax values between 16.3/1.67 and 
17.0/1.64, but not seldom I get values of around 19/1.56. 
Occaisionally even higher. These variations do not occur within one 
measurement session: repositioning and measuring again gives some 
normal measurement noise (L* +/- 0.2). But when I repeat a 
measurement a or some days later, the varations are much larger.

I do take care that I allow for drying overnight. My feeling is that 
is has something to do with changes/contaminations of the surface of 
the eboni ink. For instance, if I print a second step wedge on the 
same paper, I tend to see a roller mark on the first step wedge. I 
can't substantiate this yet, but I also have the feeling that a layer 
with more ink (giving a better the Dmax at t=0) is more prone to this 
effect (and giving a worse dmax later).

Any clues here? 

Joost