Wednesday, February 1, 2012

The next steps

I am not satisfied yet with the coffee-based developer that, for now, before I have CD4 in powder to make my own solution, and a pH meter to control this parameter in order to improve the result, will be made according to the last post.
The development of a color negative film requires 4 treatments with
Bleach and Fixer may be mixed in one bath, that is the case of the Tetenal Colortec kit. The Blix (Bleach+Fix) of Tetenal is Ammonium Ferric - EDTA plus Ammonium Thiossulfate.
Let us forget the fixer because it is the same as for B&W photography and we have to use Ammonium or Sodium Thiossulfate, dot! Other solutions like very concentrated common salt or Ammonia are too slow or produce dangerous fumes.
Let us talk about the Bleach. I found out here and I allready used it, a formula for B&W film, used to make positive B&W slides and disclosed by Hans Dietrich, 1988:
  • 9.5g Potassium Dichromate
  • 12mL Sulfuric Acid Concentrate
  • water (distilled) to make 1000mL
I have both substances at home, sulfuric acid I got at a drugstore and potassium dichromate I found at ebay and I already used it for the gum-dichromate photography. Pay attention to the safety rules when using chemicals like these. Sulfuric acid is very corrosive and potassium dichromate is very bad, can cause serious diseases and is absorbed trough the skin. SO USE GLOVES AND GOOGLES!
Well, I think this recipe can not be used like that, it must be more diluted because it can destroy the color and you will get a blank film like I got. After diluting with the double of water, and with just 1 minute bleach followed by Fixing and stabilizer, it was possible to rescue photos like this:

I used the same developer as described bellow, this bleach of Mr. Hans Dietrich and an usual fixing bath of ammonium thiossulfate. «I know not what tomorrow will bring...»

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