[pure-silver] Re: Increasing contrast of a print
----- Original Message ----- From: <C.Breukel@xxxxxxx> 
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Saturday, June 16, 2007 6:07 AM
Subject: [pure-silver] Re: Increasing contrast of a print


Hi Richard,
I have use VMI in the past with quite remarkeble results, I did not know it was for half tone, the end result was quite grainy though. I safely disposed it, I could not justify to keep it on my shelf in the light of it's high toxicity.. 

Best,

Cor
VMI is a Mercury intensifier but is not the same as Monkhoven's. Monckhoven's uses a Mercuric chloride bleach and a redeveloper containing Potassium Cyanide. The Cyanide bleaches the weaker parts of the image before the Silver nitrate in it has a chance to be deposited. As a result the low densities are reduced somewhat while the higher densities are very much intensified. I have formula for an intensifier which is supposed to be VMI somewhere, I don't think it has the Cyanide in it. Agfa 330 is an example of a Mercury intensifer which does not contain Cyanide. The negative is first bleached in the solution given below, then washed in water acidified with a few drops of Hydrochloric acid, then redeveloped in a bath of 5% Sodium Sulfite (not sulfide) or any standard, active, developer (like Dektol). 

Agfa 330
Potassium Bromide                    10.0 grams
Mercuric Chloride                    10.0 grams
Water to make                         1.0 liter
For use bleach negatives in the above until bleached to the base of the film and re-develop as given above.
I am not recommending this formula. Mercuric Chloride is _extremely_ hazardous plus I suspect is very difficult to obtain these days. My memory is that VMI is a single solution so its probably different from the above. 
   The images from Mercury intensifiers are not permanent.

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx 
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