Liam Lawless (lawless@vignette.freeserve.co.uk)
Fri, 21 May 1999 13:34:12 +0100
Michael,
Mercuric iodide is orange, and with mercuric chloride and pot. iodide in
your intensifier, this is probably what you've got, in which case it's very
toxic. It's insoluble in water, but should dissolve in pot. iodide or hypo
solutions.
Haven't seen the intensifier you quote, and I wonder if it's correct.
Mercuric chloride and mercuric iodide are both intensifiers: the iodide
intensifies directly while the chloride is used indirectly (in a bleach,
after which the neg is darkened in any one of several ways).
If you still have some mercuric chloride left, try the following (from
Clerc):
Mercuric chloride 30g
Pot. bromide 30g (optional, but recommended)
Hydrochloric or nitric acid 5ml
Water to make 1000ml
If used, dissolve the pot. bromide separately and add after dissolving the
mercuric chloride.
Bleach in the above, wash well, then darken in 3% ammonia (result not very
stable!), 5% sod. sulphite slightly acidified with a few drops of acid, a
print developer, hypo solution (for only slight intensification), or sodium
sulphide. Other things will also work, but that's enough for now.
Have used this method and it shouldn't give you any trouble.
Liam
-----Original Message-----
From: Michael F. Jacobson <jacobson@juno.com>
To: alt-photo-process-l@sask.usask.ca <alt-photo-process-l@sask.usask.ca>
Date: 21 May 1999 11:47
Subject: VMI processing question
>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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