U of S | Mailing List Archive | alt-photo-process-l | Re: Paper negatives- Ink Selection

Re: Paper negatives- Ink Selection

"If Keith were to increase his dichromate from pot di full strength to
am di full strength, yes the curve changes and I assume he would
recalibrate to make a curve for full strength.  But if I remember,
Keith is fairly loosey goosey about his practice and produces
excellent work so he may not need to."

While I do feel better that I am throwing less toxic chemicals into
the environment by diluting the sensitizer, in actuality, I am not so
much "diluting the sensitizer" as "thinning the emulsion" so that it
will spread easier.  As I think I have discussed before, I like to
humidify the paper prior to coating to make it less "grabby".  Masa
doesn't work that way.  In an interim step between humidification and
thinner emulsion, I was spraying the surface of the paper with water.
Since I was diluting it anyway, as a move towards More Consistancy and
Less Loosey Goosey I just added the water to the mix.

I'll try am di and see what that brings.  If I recall, it is a bigger
hassle to obtain am di.  More hazardous maybe?

On Thu, Oct 16, 2008 at 8:36 AM, Christina Z. Anderson
<zphoto@montana.net> wrote:
> Loris said:
> 10% AD is about equivalent to saturated PD, which is something like 13% at
> room temperature. PD solubility in 20C / 68F is 12% (according to MSDS),
> at 22C / 72F (room temperature) should be slightly more (about 13%,
> empirical).
> AD molar mass = 252.07g, 100 (10% in a liter) / 252.07 = 0.39M
> PD molar mass = 294.19g, 130 (13% in a liter @ 22C) / 294.19 = 0.44M
> and 120g PD (12% in a liter @ 20C) / 294.19 = 0.40M
> Accepting there isn't any factor affecting speed (chemically) other than
> molarity of dichromate ion in solution(!?), then in theory, due to
> slightly stronger concentration (0.44M > 0.39M), 13% PD should be slightly
> faster than (or about equivalent to) 10% AD.
> Chris says:
> Thanks for this again, Loris; will file it in my "to know" file. My next "to
> do" for education would be to take a series of chemistry classes so I can
> understand what the hell molar mass is, but it looks good to me!
> Loris said:
> What a pity! For how long it will stay? Good luck in rehabilitation...
> Chris says:
> Well, what was supposed to be 10 days ended up being 6 weeks when I awoke
> from the operation.  So you can imagine how grumpy I am.  Can you imagine
> having to have your husband drive you everywhere?  Well, no you can't, it'd
> be your girlfriend...But it has been a great experience because I am VERY
> understanding now of people's "minor" surgeries which are only "minor" to
> others (and also student absences due to surgery--I actually missed a week
> of school for the first time in my life).
> Chris