Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Paul Roark" 
<paul.roark@v...> wrote:
> 
> >>...Ironically, the smaller the particle, the
> >> larger the surface area to volume ratio is.  This larger
> >> surface-area-to-volume causes faster oxidation, which is the 
> >>cause of most fading.

Oxidation is a chemical process, not a physical one, so why would 
the surface area to volume ratio matter?    For a pigment particle 
to fade only the molecules at the surface need to change color.   
The fact that a faded pigment molecule on a small particle might 
have a zillion unoxidized molecules underneath it and one on a big 
particle might have TEN zillion unoxidized molecules underneath it 
doesn't seem all that significant since it's only the one on top 
that we see, unless you're implying that the molecules have 
motility.  (are you?)

Also note that the term "oxidation" does not necessarily imply 
contact with oxygen (e.g., air), hence the surface area exposed to 
air may not even be relevant.   Don't forget your high-
school/college chemistry - "oxidation" refers to any of a variety of 
processes that causes the molecule to give up an electron.  For 
example a bleaching agent (e.g., OCl-) is considered an oxidizing 
agent because it readily accepts electrons (OCl- + 2e- + HOH -> Cl- 
+ 2 OH-).  (anyone here remember "leo goes ger"?) This is not to 
suggest that there's hypochlorite floating around in our paper, but 
N.B. that you can achieve the same thing with exposure to UV.   

The other thing to keep in mind is that phenomena like oxidation and 
polymerization do not necessarily induce FADING - they can cause 
other color changes or even DARKENING instead.   For instance, the 
boiled linseed oil used in oil painting turns yellow, and eventually 
brown over time (decades/centuries).

The OTHER othing thing to keep in mind is that unlike painting (sign 
painting, portrait painting, etc) where the chemical and physical 
composition of the pigments in the paints is well known and has been 
widely known for decades or centuries, the physical and chemical 
characteristics of the pigments in inkjet inks is a matter of pure 
speculation.    I guarantee there is no one (or no one who's saying) 
in this forum who knows as much about the chemistry of Epson or its 
competitors' inks as the  average eager high school student knows or 
can find out about the back side of the moon.