[snip]
> >
> > Keith has just described one consequence:
> >
> > >KOx does not become
> > >exhausted. I don't know about the dichromate. I have found some green
> > >needle-like crystals in one of the bottles.
> >
> > This is, very probably, potassium tris-oxalatochromate(III): K3Cr(C2O4)3.3H2O
> >
> > The other consequence is that when the Cr(VI) of dichromate is thus reduced
> > to Cr(III) it will cease to have a 'contrast enhancing' effect.
> >
> > Mike
> >
> I guess the only thing to do to determine if Mike is right on this
> (and I have little doubt that he is) will be to repeat the test
> sequence at intervals of a few weeks and compare the results to those
> obtained with fresh KOx/NaDichromate developer. Its been several
> weeks since the first round already so I'll try to get to it this
> weekend.
>
> Anyone else (David) who has been using this method for a while have
> any observations on this count?
My experience has been that my potassium oxalate developer (which I use
at room temp.) with the sodium dichromate added as a restrainer seems to
hold up quite well. However, I have to qualify this statement because I
have not made rigorous tests.
First, as I only make up 2 liters of developer at a time, it really
doesn't last for years before I have to make more -- some gets splashed
out of the tray, some evaporates, some gets carried away with the paper, etc.
Second, I haven't had many occasions where I am printing the same image
with the same developer a year later. In the one or two instances I
*think* I recall, the developer seemed to be much the same as it was.
Now, of course, as I mentioned before I am entering the world of digital
negatives which allows me to do away with the whole issue -- one
developer (no restrainer), one paper sensitizing formula (no chlorate).
This must be heaven!
Interestingly enough, I am able to get sharper prints from my digital
negatives (to which sharpening has been applied, though not too much)
than I can from a contact print of the original negative! Neat trick.
David