QTR-Quadtone RIP

>> I would think the particle size in the suspension would be no less an
>> important parameter.

True.

>Like: http://en.wikipedia.org/wiki/Colloidal_silver

One quick source indicates particles in a colloid are typically 0.01 to
0.001 of a micron in diameter.  Companies most often claim the inkjet
pigments are about 0.1 micron.  I suspect the size, in fact, varies by
pigment, with the carbon being smaller and the weak magenta being larger
(thus helping to explain why it tends to fall out of suspension).  

> there's another possibility: http://en.wikipedia.org/wiki/Silver_nitrate

>and a reduction treatment afterwards like used in the past 
>in (silver) mirror production.

I think Jon is also using a metal-based dye in the Portfolio ink.

Where I was coming from is that there are all sorts of interesting looking
watercolor pigments that are very lightfast, but probably too heavy for us
to use, at least in for form they exist for the watercolor painters.  I
think it would be very interesting if we could access a broader range of
pigments, and tapping into an existing market would probably be the only way
individuals could do it. 

Paul
www.PaulRoark.com