Digital BW, The Print

Hi Mantinieri,

>... we noticed that it occurred most frequently in the lightest dilution (1% in our case). A quick check shown that the Ph was off ...

That's more dilute than I use.  In fact, I've moved away from the Eboni-6 2% (Y) dilution.  In both my 1400 and 7800 setups 6% is now the lightest.

> The autoprint program  requires that you have the roll paper ...

I buy "butcher" paper in large, cheap rolls for things like this.  A friend at a market here recently sold me a roll 20 inches by 1300 feet for $25.  It's the old style, un-coated stock.  I don't put the roll on the machine, but just cut a length that is enough for my estimated use.  The printer will stop if it runs out.


>... I am afraid that an ink with the wrong Ph would shorten the life of the head. 

Keeping the pH within a reasonable range is probably important for not  only the head but also the settling.  The electrostatic repulsion and stabilization these inks use are sensitive to pH.  I don't know how sensitive the systems are to the pH range.  I just did a centrifuge test of buffered and non-buffered bases and found, with the dilutions I was testing, no significant difference.  The measured pH was close for both approaches.  So, I dropped the more complex buffered alternative.  It may well be that the more dilute inks are more likely to stray outside the acceptable range. 


> ... a user replaceable head would be a better insurance.

It would be nice.

 
> Regarding Epson dithering with QTR, if you look closely, it is quite noticeable. Both HP and Epson OEM do better in that respect.

I don't doubt that the OEM drivers have special dithering algorithms that hide defects better than QTR.  However, I've found in the highlights the QTR print with a single ink is usually the smoothest looking.  As long as the individual dots are too small to see, the QTR dithering or lack thereof (I have no particular knowledge of how the alternative systems work) appears to make a smoother initial ramp.  Outside the highlights, I simply try to have enough nozzles firing that there are no significant defects to hide with the dithering.  Again, simply taking a pragmatic approach, the QTR rip works very well for me. 

Good luck with the efforts to advance carbon printing.

Paul
www.PaulRoark.com