John Navas wrote:
On Sun, 25 Oct 2009 08:21:00 -0700, "Don Schmidt" Don
red_1987 wrote in
isition:
"Matt Clara" wrote in message
...
I know it's possible to purchase "B&W" inks comprised of black with shades
of gray to replace the Cc,M,Y, cartridges in my old Epson 1270, but I don't
know where to buy inks with a good reputation for this purpose.
That's a new one to me; my inkjet printer produces shades of gray by the
amount of black it uses to cover the area being printed, no matter how small
the area.
(The white is the paper being printed on)
Gray inks produce a much superior result for critical work.
For more information, see
http://www.normankoren.com/makingfineprints4.html
They're not "grey" inks.
They're often called light-black and light-light black etc.
They are weaker (diluted) versions of black ink.
For the higher end inkjet photo printers carbon black pigments are used.
Problem with carbon black and other "black" pigments is that they
aren't black - they're usually a very very dark brown. So when they're
applied at low density, they don't look very black. To overcome that,
they add a blue/violet pigment (sometimes a dye) to make the black
neutral when applied at different densities. They do the same with
black for 4-colour (and more) litho press printing inks. All good so
far, but carbon black and the available lightfast dark blue pigments had
stability problems when used together in low viscosity aqueous
formulations, and blue dye faded too fast for archival inks.
AFAIK the first inkjet ink formulations to overcome this were Epson
Ultrachrome K3 inks, with three "strengths" of black. The data
explaining this together with example formulations is all there in US
patents.
So with neutral (or very close to neutral) at different densities,
smooth tonality was limited by minimum droplet size, so having the
ability to apply same minimum sized droplets of progressively "weaker"
ink is an advantage, and bound to be more neutral than using CYM colours
to achieve this. But some C,Y&M is still used with "neutral" black inks
- it's not perfect, Droplet size isn't fixed, Epson Piezo heads can
vary droplet size by varying amplitude and waveform of the signal (IIRC
8 sizes) HP have different sized thermal nozzles, so many more nozzles
per head, and Canon are in-between, by having several different sized
thermal elements driving each nozzle.
The results are good. You can still see the droplets with a loupe. I
can't with naked eye.