"Francis A. Miniter" wrote in
message ...
On 2/7/2011 16:04 PM, Francis A. Miniter wrote:
On 2/2/2011 23:53 PM, Frank Pittel wrote:
Richard wrote:
: On Jan 30, 5:57??pm, Frank
wrote:
: I have a bunch of long expired film that I'm working
on
developing. To keep things simple I'm using D76 diluted
1:1 and am
: having problems with fogging. I know that
Benzotriazol
should help and that Potasium Bromide may help. Does
anyone
: have experience with either approach or have other
suggestions? I'm also interested in home much much I can
add to
: the stock D76.
:
: --
:
: -------------------
: Keep working dumbo needs the money
: There is a chart showing benzotriazole use in _Modern
: Photographic Processing_ by Grant Haist. However, fog
in
negatives may
: look bad but for the most part just increases printing
time a bit,
: provided its uniform. The film should be given a bit
more exposure
: than if it was fog free. Increasing development will
increase the fog
: along with the contrast so is not useful. Bromide will
also reduce
: fog. It seems to have more effect on film speed than
benzotriazole,
: the remarks above apply to it also.
: I have been able to get rid of moderate age fog on
Plus-X sheet
: film by adding about 1 gram/liter to D-76 1:1. I shot
the film at
: about half the rated speed. The unexposed margins were
pretty clear.
: The prints were not any better than similarly exposed
film developed
: without the added bromide.
Richard,
Thanks for the quick reply. If the film were unexposed I
would pitch and get
"fresh" film. Alas, the film was exposed anywhere from
20
to 40 years ago and
there's no date on the rolls. There's a lot of fog and
it
seems to be hurting
the shadow contrast. To get any kind of reasonable print
we and the others
working on the project are being forced to do a lot of
printing with two (or
in some cases three) filters. One of the filters
generally
being a #5 so we get
some contrast in the shadows after using a 2-3.5 filter
for the main exposure.
My hope is that by reducing the fog we would pick up the
contrast in the shadow.
With minor exceptions the fog is uniform and "printing
through the fog" is
working alright.
Frank
BTW - I ordered the Haist books a few days prior to my
original post and have since
recieved it. For those that haven't seen or read it
Grant
Haist is an amazing
talent and I wish I got the books years ago!!
Some years ago, the founder of Film Rescue International
(see http://www.filmrescue.com/ ) used to participate in
this forum. He had, through long trial and error -
together
with a good knowledge of photochemistry - put together a
process for minimizing film in such situations. If top
quality recovery is your objective, you may want to
contact
Film Rescue.
He shared some information with me at a time when I was
trying to develop some 80 year old negatives (Richard
probably recalls that trial), but I promised I would not
reveal his proprietary information. And, I have to
confess,
I lost the specific email he sent, and only have
fragmentary
information now anyway.
I also note that the following is a patent filed in 1966
(now in the public domain) which describes a method of
fog
reduction in silver halide films.
http://www.freepatentsonline.com/3244522.pdf
Attention should be paid not just to the particular forms
of
xylene or benzene to be used, but also to the specific
development processes described.
Here is another relevant patent in the public domain.
Again, note the details that the two processes have in
common: http://www.freepatentsonline.com/3226232.pdf
--
Francis A. Miniter
Its good to see you are still here Francis. I do
remember the thread. I also talked to the guy. He gave me
some hints but not the actual process. We talked enough to
convince me that he knows what he is doing.
A good source for patents is Google Patents. One can do
a complete text search on all US patents ever issued and
download them as PDF's, much more convenient than the Fax
TIFF files from the USPTO.
--
--
Richard Knoppow
Los Angeles, CA, USA