Re: Reversal processing for enlarged negatives

On Thu, 25 Mar 2004 oakcask@mm.st wrote:

> It's hard to believe that what you saw was due to fixing by the small
> amount of thiosulfate in KRST. Kodak MSDS says 27% of the stock
> solution is ammonium thiosulfate. By the time you dilute to 1+14, it's
> 1.8%. This isn't enough to fix prints that fast. Bleached crystals are
> often more difficult to fix than original crystals. What bleach did
> you use?
>

I estimate that I toned about a thousand prints (maybe more -- I had
something like 15 cases of old Brovira, with 10 boxes per case, 50 sheets
per box) so I was pretty familiar with the operation. It's quite possible
I was using a stronger KRST... this was more than 20 years ago, and only
one or two prints, because I didn't do it again. However, if 27% of the
stock solution is ammonium thiosulfate, I would not expect, even at 1:10
much image potential to remain.

I mostly used copper sulfate bleaches, with various acids & potassium
bromide, or other... or it could have been a ferricyanide bleach... But it
clearly wasn't a useful procedure. I also found, however,that infinitesmal
amounts could have a very profound effect. I used to use a pre-bath of 1
drop of a 20% solution of a sulfide mix in a liter of water for 30 seconds
before bleaching and it gave a distinctly different effect... It's
probably a mistake to even mention, because I don't remember specifics and
don't feel like looking them up... but it comes to mind a propos of the
effects of very small amounts. In fact I was so surprised I asked the
chem prof at school -- how could 1 drop of a 20% solution in a liter,
etc. etc.... His explanation was, my dear, there are billions of ions in
everything. (Though maybe he only said millions.)

> > selenium got hard to get. I had/have a bunch of it, but it was claimed to
> > be poison... And for a while at least as expensive as gold.
>
> Yes it's a poison but it's a bit surprising to hear that from a person
> who isn't afraid of formaldehyde, ammonia smell, dichromate, and what
> not...

Actually I thought the fuss about selenium poison was a lot of ado about
very little. I was very carefully putting a small quantity in water. But
there seem to be different forms -- mine is NOT powdery, but quite
granular. I mentioned the poisonous part because when I wanted to get
more, I was given that as reason for unavailability & it may still obtain.
However I do think the smell, or the poison, or whatever, should certainly
be mentioned when others not familiar with a material are listening. Don't
you? Does mentioning it mean you're afraid?

In fact we already had a big tsimmis about this on the list... It may have
been exactly this topic. I was probably being scolded for using selenium..
with the kind of hysterics those photo hazards books (which assume 40
hours a week of industrial strength participation) provoke. I think it was
Sil Horwitz who pointed out that we require trace elements in our diet,
maybe to keep our fingernails from breaking, and people take selenium
pills if they don't have enough in their hair ! (It occurs to me to
mention that this last is meant to be funny. Sorry if it isn't.)

Judy

I make my best favorite toner (selenium plus polysulfide) from
> scratch because both AGFA and Kodak discontinued the product, and to
> my knowledge, there's no one else who sells anything comparable.
>
> --
> Ryuji Suzuki
> "All the truth in the world adds up to one big lie." (Bob Dylan 2000)
>
Received on Thu Mar 25 21:11:46 2004