IIs this what you meant to say?: While the use of HCA can extend the capacity
of the
fixing bath it does not take the place of thorough fixing. Atop bath
extends fix life. HCA reduces wash time.
On Tuesday, February 16, 2021, 07:43:52 PM EST, `Richard Knoppow
<dickburk@xxxxxxxxxxxxx> wrote:
Since this started out being about the processing routine for
toning and then became just the processing routine I wanted to
add a couple of notes from my research. For negatives and prints
to be reasonably permanent they must be fixed and washed
thoroughly. While the use of HCA can extend the capacity of the
fixing bath it does not take the place of thorough fixing. The
use of the test solutions, Kodak ST-1 and HT-2 can take a lot of
the guess work out of this. In the past various indirect methods
of measuring both fixing and washing were used, all had
shortcomings. These two are direct and can give one a very good
idea of whether these two steps of processing are being done
adequately.
Trying to stretch the capacity of fixer is a sure way to
shorten the life of the material. So is skimping on washing.
When a sulfite HCA is used the washing should follow the
manufacturer's instructions. In particular, Kodak knew that when
HCA was used one could over wash and its instructions are
intended to avoid that. Nonetheless washing is probably safe if
one does not indulge in the technique of multiple hours long
washes or overnight soaks. If Kodak recommends washing for twenty
minutes and you wash for an hour its probably OK.
Secondly, certain toning processes much extend the liftime of
the material. The most recent research (and its actually pretty
old now) recommend partial toning of both prints and negatives in
a polysulfide toner. Even a slight toning in a sulfide toner
provides substantial protection against further fulfiding or of
oxidation of the image silver. In general it can be accomplished
without a noticeable change in image color or density. Where
some color change is acceptable or desired other toners can be
used but, in general, they do not provide full protection unless
the images are toned to completion.
Toners that substitute alkaline minerals for the silver,
such as Iron Blue toner or Copper toner may produce beautiful
results but are less permanent than the original silver. They can
be used for display prints that are not intended to be permanent.
The sulfiding toners, like hypo-alum and indirect (bleach and
redevelop) toner are very permanent when toned to completion but
both and some some others like selenium toner, are not uniform in
their actions, tending to tone the less dense parts of the image
before the denser (and larger grained) parts. Polysulfide, on the
other hand, tones all densities at the same rate. Actually
selenium toner also provides quite stable images when used to
completion but the old recommendation of partial toning in highly
diluted toner was found ineffective.
I don't know about Nelson's Gold. It is a sulfiding toner
which is reputed to tone all densities evenly. It requires the
images to be re-fixed after toning, probably due to the
production of some silver halide during the toning process. It is
probably as permanent as polysulfide but, AFAIK no one has tested
it. I think the gold content makes no difference except in the
image color.
Kodak Gold Protective Solution, once the standard for
treating for permanence has been found to be essentially a
sulfide toner where the presence of the gold has little or no
effect (see IPI research reports). Polysulfide is more effective
and lots cheaper.
There is a gold toner for blue images. AFAIK this produces
permanent images. It is a better choice than Iron toner where
long life is desired but is expensive. Images toned in Iron which
have faded can sometimes be regenerated in the same way that
blue-prints can.
You all now know everything I do until I send this and
remember something I left out.
--
Richard Knoppow
dickburk@xxxxxxxxxxxxx
WB6KBL
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