[pure-silver] Re: Mercury Intensifier (VMI): was Increasing Grain
- From: john stockdale <j.sto@xxxxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Sat, 17 Jun 2006 11:28:22 +1000
Jerry, Eric and Richard,
Thanks for your comments. I know the facts of life (i.e. that intensifying
a neg with minimal shadow detail can't improve what's not there). In
Anchell's Darkroom Cookbook he does say that VMI can improve such negatives
where other intensifiers could not.
Richard, the VMI formula is used without a preliminary bleach. The orange
intensified image can be made permanent by soaking in sodium
sulphide. Overintensification must be avoided since it leads to orange
powdery deposit on the film.
Here are some notes by Bill Troop that give me some encouragement. It was
in an article about pushing etc. His comment that the ingredients are
"caustic" may be true, but "dangerously poisonous" should have been
added. I doubt that the intensification is a "dye stain" as he states.
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<Start of quote from Bill Troop>
VMI Intensifier
It may sometimes be necessary to further intensify negatives in order to
increase the contrast to printable levels. For this purpose I use a formula
known as Smith-Victor VMI.
VMI creates a dye stain which increases the overall density, revealing
shadow detail you didn't even know existed. Unlike most other intensifiers,
VMI especially strengthens detail in the thin, weak areas, creating greater
separation of tone and increased contrast. From one to three minutes will
intensify your negative approximately two to three times. If you over
intensify, or change your mind later, VMI can be completely removed by
immersing the negative in hypo and rewashing!
The only drawback to using VMI is that you have to mix it yourself and the
ingredients are highly caustic. The formula is as follows:
Smith-Victor VMI
Mercuric chloride, 13.0 grams
Magnesium sulfate, 60.0 grams
Potassium iodide, 30.0 grams
Sodium sulfite, anhydrous, 15.0 grams
Distilled water to make 1 Liter
(Note: All chemicals to make VMI formula can be obtained from Tri-ESS
Sciences, 1020 West Chestnut Street, Burbank, California 91506; (818)
848-7838.)
Be careful not to inhale any of the powders before or during mixing. Always
use a dust mask with ample darkroom ventilation. Also, use rubber gloves
when handling caustic chemicals such as mercuric chloride, whether in
powder or solution.
A sediment will form at the bottom of the bottle. You may filter it out if
you wish but either way pour as little as possible into the tray when you
intensify. If sediment does settle on the negative it may be removed by
carefully brushing the wet emulsion with a wet cotton swab.
The negative to be intensified should be thoroughly fixed and washed.
Sometimes, after developing film from an available-night session I can tell
that the negatives are too thin. In this case, I intensify the entire roll
while it is still wet. To do this I leave the film on the developing reel
and after washing immerse it directly into a tank containing the intensifier.
If the film is already dry it should be resoaked for at least five minutes
in plain water before immersing in a tray containing the intensifier. Using
a black tray will cause negatives to appear as positive images which helps
to judge the density increase. As in any after-processing technique handle
the negatives with great care to prevent damage to the emulsion.
After intensification, wash for 10 minutes, soak in wetting agent, and hang
to dry. To make the intensification permanent, soak the negative in a 1%
solution of sodium sulfide for a few minutes.
<End of quote from Bill Troop>
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