Great, thank you. So for FB paper 2-3 min in each bath (sodium fix no
hardener), followed by 5 min wash, hypo clear, followed by 30-40 min wash
(or water exchange) sounds about right as well.
So far my regime was 1-2 min in Ilford Hypam 1+4, single bath, no hypo
clear, wash up to 1 hour.
V sre., 6. nov. 2019 20:59 je oseba `Richard Knoppow <dickburk@xxxxxxxxxxxxx>
napisala:
In older books on processing one finds three grades of
washing: 1, is for short term use, that is, something that is
expected to last for days or weeks, 2, commercial, such as photo
finishing, expected to last for some years, 3, archival, supposed
to last forever (or at least many years). These were specified by
the amount of residual thiosulfate measured in various ways. It
turns out that the "commercial" or medium thorough washing had
longer life than the "archival" washing, which was specified to
have NO residual thiosulfate. If a print or negative is toned
this makes no difference. For many years the use of selenium
toner was the standard for microfilm but it was found that for
some reason the use of Kodak Rapid Selenium Toner was not
effective so some microfilm, which had been in storage for a
relatively short time, was showing signs of image degradation.
The use of gold toning, which was the gold standard (no pun
intended) works fine but is quite expensive. So another toning
method had to be devised for regular use on microfilm. This
turned out to be a type of sulfide toner which tones all
densities the same. This was the failure of KRST, it did not tone
light densities the same as darker or more dense densities.
Evidently, something had changed in the toner although Kodak
claimed they had made no change. A polysulfide toner was found to
work where only a small amount of toning was wanted for the
purpose of protecting the image against oxidation and further
sulfiding. Actually selenium works if its carried out far enough
but for microfilm, which is especially sensitive to attack by
atmospheric pollutants, toning must not be carried out to the
point where it affects the color and structure of the image. For
pictorial photography this does not make a difference. In any
case, The Image Permanence Institute devised a polysulfide toner
especially for this application although standard Kodak PolyToner
(now discontinued) works fine for general photography.
By leaving a very slight residue of thiosulfate in the
emulsion a degree of protection is afforded although not so good
as with a suitable toner.
Any sulfiding toner or selenium toner, carried out to
completion will result in very permanent images but will also
produce a change in color which may not be desirable. The
importance of image structure in microfilm is because it is
important to preserve the very fine image structure, not
necessary for pictorial photography. Only a few toners will
provide protection without full toning, polysulfide and gold are
among those that will.
We are talking about images intended to last a couple of
hundred years. One indication that "commercial" processing
standards can be archival (sometimes) is that there are so many
snapshot pictures in people's collections that are more than a
century old and in perfect condition despite storage under
non-archival conditions. Helps us because it does not require
some of the overblown washing techniques in some of the books
from the 1950s. In particular, overnight soaks and similar
treatment can damage fiber support, bad practice but recommended
in a lot of places.
Well, we now have digital and everything will last forever.
Won't it? You mean digital wears out? Oh, dear...
On 11/6/2019 11:25 AM, Miha Golobic wrote:
Dear Richard, I have read many of your posts answering similar
questions, however this one seems to be the most comprehensive so
far. Thank you very much for taking the time and sharing your
knowledge.
There is, however, a claim in your post that piqued my interest -
you said:
The old commercial standard of washing turned out to be much
better.
Can you shed some light on this commercial standard of washing
method?
Miha
--
Richard Knoppow
dickburk@xxxxxxxxxxxxx
WB6KBL
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