Michael F. Jacobson (jacobson@juno.com)
Fri, 21 May 1999 07:16:50 -0700
Need some help with the following;
I've got some very thin 35mm Tech Pan Film exposed at EI 200, developed
in C-76 for five minutes and after some struggle attempting to lith
print, I decided to intensify the negatives in Mercuric Chloride.
The prints of the negatives were thin and muddy on grade 5
Ilford MC IV RC as well as Sterling lith paper developed in
dilute lith.
After a water bath of 10 minutes the negatives were intensified
for 2 minutes in VMI Mercuric Chloride and washed for ten minutes,
photo-floed and dried.
Mercuric Chloride 13 grams
Magnesium Sulfate 60 grams
Potassium iodide 30 grams
Sodium sulfite, anhydrous 15 grams
Water to make 1 liter
After intensification the negatives have red-orange "salts"
covering them. On extreme enlargement to crop 1/4th of the image at
11 X 9 (image size) the "salts" appear on the print as white spots in
the black areas of the print, a veritable snow storm of "dust." A friend
suggests the formation of the "salts" may be a result of differences in
temperature in the intensifier solution and the wash water.
Unfortunately, the water bath and wash water were both 15 degrees
warmer than the intensifier...
The granularity is not a problem *in* the film, it's a problem on the
film.
The red-orange dust is truly a dust and wipes off onto negative sleeves,
cotton swabs, anything it comes into contact with. (Washed for 10 min.)
It just won't all wipe off at one time or without extreme scrubbing,
something I'm loath to attempt.
The highlight areas of the film are intensified with a yellow-orange
mask,
that's as it should be. The problem is with the red-orange "dust."
The shadow areas are essentially clear film and most of the film is
shadow.
The whole film has the red-orange "dust" of an apparent precipitate
"salt" that can be somewhat removed by gentle swabbing with cotton.
The "salt" builds up more heavily in some areas of the film than
others and has to do with the position of the film in the intensifier
rather than areas of density. I realize the color of the silver
changes with the intensification to yellow-orange, the "salts" are
another matter, another color. I'm trying to identify possible solutions
before moving forward with more testing. The intensification is slight,
only two minutes in the intensifier. Has anyone seen red-orange "salts"
as
a result of this process and do you know what was done to remove them?
Would a solution of sodium sulphide remove the salts, or make them
a more permanent problem on the film?
The possible reasons for the "salts" I see as these:
Differences in temperature in the intensifier and the wash water.
Failure to filter the intensifier before use.
Chemical contamination in the dish.
Chemical contamination from the wash cycle. (chemicals in the water.)
I've contacted my chemical suppliers and as yet, no one has an answer.
Someone must have seen this before... I hope...
Further tests I will carry out:
Fix one strip of film, hypo-clear, wash, strain the intensifier,
re-intensify (in a tray cleaned with fix, cleared, washed),
re-wash (in a try cleaned with fix, cleared, washed), re-photo flo
and dry. (Insuring of course that the temperatures of the solutions
are within a few degrees of each other.)
If that works, fine. If not...
I'll treat one strip with the recommended solution of sodium sulphide
to see if it will remove the red-orange surface "salts" in addition
to making the change to the image permanent.
If that works, again fine. If not...
I'll test the wash water for the amount of time vs precipitation of
"salts."
If the wash water is reacting with the intensifier, I'll test washing
with distilled water.
Comments, suggestions, folks to contact???
Tala Brandeis
brandeis@pacbell.net
415 584-3530
2215-R Market Street
Suite 247
San Francisco, CA 94114
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