Re: Opacity of digital negative substrates, was Re: Gum a la Sam Wang

I think why the speed question to Sandy, aside from finally having found a
way to get a digital negative to work for me, is environmentally how little
dichromate can you get by with and still print a gum print in a reasonable
amount of time with the correct contrast.

If I am now able to use 1/5 of my usual dichromate concentration, and still
print my negs usually (it is seeming) for 1/2 minute to 2 minutes even
under UVBL, I'm thrilled.

What it *seemed* to me is that with an increase in dichromate at a certain
point, in practice, it does nothing to speed the process along and only adds
to lowered contrast. And there's more dichromate yellow stain in the
borders of the print so it adds to clearing time, too. That point where
speed benefits end and lowered contrast (if not needed with a digineg)
begins is drastically lower than I figured, and may even be lower yet
according to Sandy's calcs, altho I do not have time to put it into practice
with a test wedge and pigments. I'd like to do this with say, a 1%-5% di
solution for instance. And then go back and redo a couple of my Kodak Direct
Dupe negs. Christmas break is coming...(here I am in my pj's at the computer
and I have to go TA in 1/2 hr....)
Chris
PS forget the more expensive Pictorico if you have a 2200 anyway. A $20
pack of 50 sheet Apollo Ink jet transparency film from Office Max works just
fine--you won't gasp as much when you blow a negative.

> Somewhere along in here Sandy made an analogy to carbon printing, or
> anyway dichromate exposure with gelatin. I HATE to be wrong in print, but
> I have an idea that analogy doesn't hold. I don't see how you can talk
> about *speed* for a gum print without the variable of pigment
> concentration -- or at least some reference to that -- or at least how the
> "speed" is to be figured, unless of course the referent is gum +
> dichromate tone only.
>
> Although I've done various tests on Pictorico, I haven't printed with it
> enough to speak with assurance of its printing qualities (tho I still
> doubt it's slower than film as seems to be the consensus here -- tho maybe
> it was the black ink that blocked less UV than silver blocks, even though
> it read the same on the Macbeth.???)
>
> HOWEVER, that issue aside, how do you measure "speed" when you're adding
> pigment -- say, SO MUCH pigment that the steps block up, so you only have
> 3 instead of 5 or 6? Would you measure by the top step? But even then
> you couldn't count just the substrate, you'd still have to factor the
> variable of pigment & amount of pigment.
>
> ?
>
> J.
>
Received on Mon Nov 24 06:15:21 2003