I will be glad to send a .pdf file of an excel spreadsheet that graphs
the UV transmission density of the 8 ultrachrome inks on the Epson
x800 series wide format printers and the Epson 2400 printers. What is
interesting is that even though these two printers ostensibly use the
same inkset, the way that the printer lays down the ink is different.
It is pretty informative and puts some of these musings in a visual/
quantitative form. Just email me offlist at clay (at) clayharmon (dot)
On Apr 12, 2009, at 10:56 AM, Christina Z. Anderson wrote:
Thank you for finally chiming in on this issue, when Loris asked the
original question of why does cyan and yellow together hold back
more light than one would presuppose from the way they individually
hold back light? Your answer raises some interesting points.
I have posted my bw paper example here for what it is worth
(apparently nothing to certain listees) for an illustration of color
under tungsten not UV light:
Now, let me get this straight:
1. Alberto said: (cut)
Perhaps one response might have been: because adding another UV
blocker to that contained in the yellow ink increases the total
opacity towards UV.
UV absorption of an organic molecule relies mostly to the presence
of double bonds. How many they are -and their UV absorption- is
almost independent on the visible color: you can have a perfecly
transparent substance in the visible range which is UV opaque. A
factor 30 sun oil is not black, only perhaps very faint yellow...
I don't know what molecules are in the inks the different printers
and their different models use, but considering also the additives
that certainly are in the inks, there are many reasons for
believing they all are different enough.
This is a PERFECT example to tell my students! If you remember, the
original intent of my circles was to show students that the relative
lightness/darkness of a color does not predict how well it holds
back UV light. But now I will couple that with the sunblock
example!! Excited. So your answer/conjecture (?fact?) to Loris'
question is the presence of more double bonds in the colors mixed or
in the stuff the ink is suspended in. I suppose it'd be a cold day
in hell before Epson would tell us any of this proprietary info. Not
that I care in the long run as practice is what is important.
2. Alberto said:
> What I was trying to say in my previous post was that it is a
infer a UV absorption from the visible color of a pigmented matter,
whatever it is. All the arguments about complementary colors
(yellow/blue, red/magenta, etc) hold only in the visible range.
It is nonsense, but not to Twentysomethings :) But apparently
Loris, myself, and others find yellow in the Ultrachrome inks to be
the densest, whatever the reason if not its color (on 6 different
printers for me, but all Epson) but that is not a quantative fact,
because it does not related necessarily to dye based printers or HP
printers...but it seems I should be careful to "couple" its UV
blocking nature to its color opposite the UV spectrum as I think you
are saying. I will stand corrected.
Now, a question for Loris and then back to Alberto:
3. Loris, you said that you "know" that printers do not lay down
more ink when mixing a color. Is that a for sure fact or a surmise?
Because let's just deal with the visible light example in my BW
print then. If you see, the combination of yellow and magenta to
produce red holds back the most light, but if you look at the yellow
alone and the magenta alone it is hard to make that "leap" from
those darknesses to the combination of the two colors, which holds
back more light than even black. Which, at least for me, provides
more food for thought about the printer drivers. But if you KNOW
that is a fact then I will remove that conjecture from my mind.
4. Alberto, did you at all get affected by the earthquake? It has
been on the news lots here and I offer condolences. It makes the
puny blow up downtown Bozeman pale in comparison. I hope you were
nowhere near/had no relatives affected :(