Digital BW, The Print

Hi everyone!

3 weeks ago I encountered an annoying thing: I noticed that my fresh 
B&W quadtone prints were different when I compared them with older 
prints of the same file. As if the tones had shifted, with loss of 
detail. And the step wedge I printed looked bad: some of the steps in 
the middle area almost blended into each other. Something was not 
right, and it had to be the I N K, because when I printed pure 
swatches of black, Y, M and C (to be able to view, on the print, the 
pure, unmixed B&W inks) I could see and measure that it had changed 
compared to how it used to be (I compared it with a print of the same 
swatches I luckily made about a month ago).

I applied an extra Photoshop curve to "repair" this, and it
worked quite well. 
But now, 3 weeks later, it happens again! Again the prints and step 
wedge have changed! I don't want to go one and one adjusting each 
time, because it is a lot of work. And it is very frustating to know 
that your results are not consistent.


Now, how can it be that inks change tone? I could think of some 
reasons:

-they changed the receipe, down in the factory. By mistake or on 
purpose. Can that be?

-the inks have got too old. They are about a year old, I guess. 
Possible?

Is anyone familiar with this problem? And what should I do about it, 
because it drives me nuts?

All the time I've been using an Epson 1160 with B&W Sundance
Neutral Warm Inks (formerly PiezographyBW), and use the Photoshop 
curve that Paul Roark kindly provided for this inkset. 


Thanks in advance.

Igor Wesdorp
Amsterdam