[pure-silver] Re: Increasing contrast of a print
----- Original Message ----- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx> 
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Saturday, June 16, 2007 7:44 AM
Subject: [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
A more practical intensifier is Kodak In-6. Kodak calls this a Quinone-Thisulfate Intensifer and claims it give more intensification than any known single solution intensifier. The image is not permanent and is destroyed by acid fixer. FWIW here is the formula: 

Kodak In-6 Intensifier

Solution A
Water (at about 70F)                    750.0 ml
Sulfuric Acid                            30.0 ml
Potassium Bichromate                     22.5 grams
Water to make                             1.0 liter

Solution B
Water (at about 70F)                    750.0 ml
Sodium Bisulfite                          3.8 grams
Hydroquinone                             15.0 grams
Kodak Photo-Flo                           3.8 grams (sic)
Water to make                             1.0 liter
(Note: Two editions of the Kodak formula book give the amount of Photo-Flo in grams. Its probably supposed to be milliliters) 

Solution C
Water (at about 70F)                    750.0 ml
Sodium Thiosulfate (crystaline)          22.5 grams
Water to make                             1.0 liter
Use distilled water for all solutions. The presense of chlorides in amounts greater than about 15 parts per million will impair the intensification. For use: To 1 part of Solution A with stirring add 2 parts of Solution B, then 2 parts of Solution c; continue stirring and finally add 1 part of Solution A. The order of mixing is important and should be followed. The stock solutions will keep in stoppered bottles for several months and the mixed intensifier is stable for two or three housrs without use. Bhe bath should be used only once adn then discarded, because a sued bath may produce a silvery scum on the surface of he image. Wash the negatives for 5 to 10 minutes, harden in Kodak SH-1 for 5 minutes and wash again for 5 minutes before intensification. For highest degree of intensification, treat for about 10 minutes at 68F (20C), then wash for 10 to 10 minutes and dry as usual; for a lower degree of intensification, treat for shorter times. Agitate frequently to avoid streaking. Treat only one negative at a time when processing in a tray. The usual precautions for the use of Sulfuric acid and Potassium dichromate apply; both are hazardous materials. 

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



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