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

On Thu, 27 Nov 2003, Sandy King wrote:

> Judy Seigel wrote:
>
> >
> >> One of the obvious problems in carrying out this kind of test with
> >> gum is that you would need to be able to weigh accurately extremely
> >> small amounts of dichromate. For example assuming that you took as
> >> your norm 10ml of coating solution, to run tests with sensitizers in
> >> the 1% to 10% range would require that you be able to measure
> >> accurately from as little as 0.1g to as high as 10.0g.
> >
> >To put it mildly. And, as noted, no particular reason to do so. Or none
> >that I can see.
>
>
> Judy,
>
> The reason should be obvious. Protection of *your* environment. The
> way you work results in pollution of the environment with more
> dichromate than is necessary for the application. Just do the figures
> and and show me if I am wrong,

Sandy,

I think we're talking about 2 different things... I'm addressing the use
of dry dichromate. What seems implicit in your reply is the assumption
that you use less dichromate if you use it dry -- rather than the same
amount per print only dissolved in water. Why would this be? I've always
diluted the dichromate solution well beyond the standard 26% or even 10%,
hence used less, since I find that coating & developing work better with a
thinner emulsion. I think probably my present practice remains heavier on
the dichromate than 1/2 of one percent, tho I haven't checked YOUR math on
that figure !!! -- but, math aside, perhaps you can explain why suitable
dilution can't be made up & used accordingly.

Not to mention that in my experience it's next to impossible to measure
out dry dichromate without having fly-around particles, which would by
"dry" system occur with every print -- as would of course be more harmful
to me and my PERSONAL environment than trivial amounts (what isn't
oxidized or hardened into image) entering the water course, that EPA told
me was removed anyway in treatment plant. On top of which, as i do mop up
of work area, and the particles then enter the water stream, I daresay at
least the same amount total dichromate would be ultimately dispersed, not
to mention the effect on my IMMEDIATE environment, which could at some
point remove me from other good works.

Judy
Received on Fri Nov 28 15:52:20 2003