Digital BW, The Print

Paul Roark wrote:

> humidity or paper batch.  It may be that the amount of water that needs to
> be absorbed by the coating is so much less than it is designed for that
> humidity is a minor influence.

Nice to see that my fears are not proved in practice. While 
theoretically more total dot boundary length versus dot 
surface should make dotgain more difficult to control (in 
offset printing this is one of the problems when finer 
screens are used)  the actual ink media amount with BO may 
never touch the coating's absorption limits and with diluted 
inks of a quad set it will exceed that absorption limit much 
faster.  Should remember that as it probably is a general 
rule in inkjet printing. Wonder whether the printed surface 
may be a bit more vulnerable if the ink stays more on top.

> One other thing I'm seeing that might be relevant to this issue is that some
> papers that showed blotchiness with dilute inks look fine with the 3-Eboni
> approach.  MIS Alpha, which is the Innova un-brightened coating on an alpha
> cellulose base, is a dramatic case in point.  My favorite paper for several
> years was the PermaJet Alpha, which was this same coating, but on a cotton
> base.  It printed smoothly with dilute inks and had a wonderfully creamy
> tone.  Then PermaJet pulled out of the U.S. market (when Jobo USA folded).
> MIS tried to replace this, using the "Alpha" name on the alpha cellulose
> base, but it never printed well.  It was a huge disappointment.  Now,
> however, it's back.   The MIS Alpha looks terrific with the drier printing.

Right there's no ink media enough and/or not enough paper 
surface covered to show that blotchiness. Cheaper quality 
coatings in general may perform better too then. In all the 
quad ink curves the transfer points between the quad inks 
have the highest ink loads + the 100% black but in this case 
only the 100% black gets there and that isn't transparent 
enough and as you write here below drier than with a single 
head.

> I've also noticed that I reach, at least with some papers, the dmax using
> less total ink with 3 channels firing evenly than I do when I have one
> channel carrying most of the load.  This reduces ink usage and makes
> optimizing dmax much easier than it was when the Eboni channels were not
> firing equally.

Wonder whether the smaller droplets from more nozzles 
evaporate more ink media in flight too. The distribution on 
the surface will be better and then black Dmax usually goes 
up but it could also be less penetration into the coating 
that happens. Not better Dmax but the same Dmax at a lower 
ink limit, touching the minimum reflection point of black 
pigment inks earlier with that uniform black layer on top of 
the paper coating. I have a suspicion that thermohead inks 
have that too, the HP desktops often behaved better on 
uncoated papers.

>> First of all its ratio between dot surface 
>> and total dot circumference shows changes faster
> 
> I'm not sure I follow why they'd change faster.

If bleeding for one reason or another happens then the same 
tone made with more small dots suffers more than a tone that 
is made of less large dots. But forget this, it looks like 
bleeding is no issue here, even on papers that do not have 
the best coating.

>> and the black ink has little transparency
> 
> That, I think, is the key.  Ideally, I'd like little black holes.  It's the
> minor transparency at the edges that is, I believe, one of the remaining
> sources of warmth.  When you look at the 100% black tones, it looks like
> Eboni has very little warmth.  At the other extreme, when diluted, it's as
> warm as any.  I think the smaller the edge transparency the less influence
> on tone the carbon will have.  As such, the ratio between the area and
> circumference is probably why the 3.5 pl 2200 dots print a bit more neutral.

Right there should be a bit more neutrality with larger 
dots. Good coatings should improve that too for small dots 
though.

>> At the same time the small black dots give the graphic 
>> qualities Clayton liked: paper color less filtered overall, 
>> ink color hardly visible, high detail contrast.
> 
> The less-filtered paper is mostly what I'm seeing.  The paper becomes even
> more important.  Again, I'd like little black holes with no color at all.
> Eboni may be the best we can do with current technology.  (I would like to
> test some other black inks, however.)  It's rather ironic that after all the
> variable tone inksets I've made to help control the tone of the print, I'm
> now taking a totally different direction.  However, it was really fighting
> that carbon warmth that was behind all of the other efforts.

Yes, it is a real change in thinking but not strange for 
B&W. For subtractive color printing it is the opposite, the 
CcMmY color filtering works best with continues layers, 
there the limit is how much detail contrast can be kept. The 
N-color printers like the HP Z3100 reduce the ink amounts 
with the RGB ink substitutions for CM etc mixes, one way to 
deal with it. It is quite remarkable that the LM ink in that 
printer is the least used of all.

>> and by that of inkmedia so reducing outgassing to a minimum 
>> when framed.
> 
> I've never had a problem with matte paper outgassing.  The glycols that
> cause the outgassing apparently have a great affinity for cellulose.  So, on
> the non-barrier papers, they seem to latch onto the paper and just stay
> there.  I have wondered, however, what impact they have on longevity. 

Sorry, I made a jump there to gloss printing without 
mentioning it. Anyway I do not see why Multihead BO with PK 
shouldn't work for gloss. The R1800 GE could help if gloss 
isn't that good, possibly better in a second run though to 
keep the same dry ink quality of BO in the image printing stage.

Met vriendelijke groeten, Ernst


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