Digital BW, The Print

John Labovitz wrote:
>
> On Jan 10, 2008, at 8:28 AM, pr_roark wrote:
>
> >  I hope others join me in exploring the  possibility
> > of a darkroom style carbon ink mixing approach.
>
> I'm with you!
>
> My old 7500 has been gathering dust here for a while, ...

Mine is now pumping out nice carbon prints. These old workhorses,
hopefully, have a lot of life left in them for these specialized
purposes.  I think these old machines are getting rather cheap also if
one can find them in good condition.

...

> Speaking of process, could you explain your physical setup of your
> testing environment?

It's actually rather simple and I'm sure from a chemist's perspective,
very crude and unsophisticated.

A good digital gram scales that can read to 0.1 gram is important.  To
mix large volumes of base, being able to read up to a reasonable level
is also important.  I'm using an OHaus Scout II that reads from 0.1 to
1200 grams.   http://www.americanweigh.com/
<http://www.americanweigh.com/>  shows a whole range of scales that
gives an idea of what one can get at different price points.  B&H has
one that they've probably found is appropriate for darkroom work.  Don't
limit the top side so much that you can't mix a decent amount of base at
a time.

My viscosity measuring device will particularly amuse the sophisticated.
http://www.paulroark.com/BW-Info/Viscosity_Comparisons.pdf
<http://www.paulroark.com/BW-Info/Viscosity_Comparisons.pdf>


>  Do you use funnel carts?

No.  First, I do my testing on a smaller desktop unit.  Then after I'm
convinced the mix is good enough I load a traditional 7500 cart.  They
can be rinsed and re-used easily.

For the desktop testing, the easy-refill types of carts for the 220,
1800, 2400, C88, etc. are the easiest to experiement with because they
can be re-used many times.  I used a 2200 for testing for a while, but
ran out of sponge-type carts, which cannot be rinsed and re-used
effectively.  I then started to test on the 1800, which worked OK, but
it is not very representative of most Epson printers due to the small
drop size.  Now I'm using a 220, which is close to ideal, but no longer
made.  The C88+ is still made, apparently.  That is a cheap and easy
test bed, even if not so good for seeing what densities will work best
in a hextone print, since the C88 is a quad.

Actually, though, I do most of my testing on just the LLK density,
because that is the one that affects the tone the most.  With a
magnifying hood, 1600 dpi scanner and spectro, I can see smoothness and
tones rather well with just that one mix.  When I have a mix that looks
very good, then I take it to the full hextone mix in the 220, profile
and print for a while to see if I like the results.

I've been using a hextone dilution system that gives me the
"traditional" densities we've been using for some time now.  However,
I'm thinking of abandoning that and going to one that is the easiest to
mix and would be easy to test and use on a quad, but with 2 densities
omitted, of course.

> How do you handle the waste ink?


That raises an interesting question that I don't know the answer to. 
Since I test with 20 gram mixes, there isn't that much volume.  The main
ingredients are water and glycerol, which should be harmless.  The
darkroom chemicals may be the worst.  I'm on a sewer system and dealt
with the city sewer people when I put in the darkroom.  They concluded
that small volumes of what I was using, including Photo Flo, were not a
problem.   The Microdol-X MSDS bothered them the most, and I had to
agree not to develop more than 3 rolls per day using that developer in
order to get the permit and dump the chemicals into their sewer system.
So, I think I'm probably within what the city seemed to think was
harmless to their system, but if I were doing this on a commercial
scale, I suspect I'd have to have a chemical disposal system that was
other than the sewer system.

Paul

www.PaulRoark.com <http://www.PaulRoark.com>



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