Friday, 9 December 2011

Farmers reducer.

This is a follow on from my last post on reduction.

Over developed or over exposed negatives may need to be reduced to make them a better printing prospect. This is achieved with chemicals that strip silver from the final image. Like developing, reducing a negative requires practice so you get an idea of how much to take away. It is best carried out in a place that is well ventilated with diffused light so you can see the process at work. It is a good idea to pre-soak the film it will allow you more control by slowing the process down. With experience you will get to know at what point to remove the negative. The chemicals do not stop working instantaneously. Because you can repeat this procedure it is better to reduce the negative in small steps so as not to over do it.

Reducers can be supplied ready mixed or you can mix your own. The formula that follows is a proportional reducer for overdeveloped negatives:

Stock Solution A

  • Potassium Ferricyanide 7.5 grams.
  • Water 1 litre.

Stock Solution B

  • Sodium thiosulphate (Hypo crystals) 200 grams.
  • Water 1 litre.

Notes: Ferricyanide has good keeping qualitys if kept out of strong sun light. Once you have mixed the chemicals you should use immediately. If you are using a stepped method of reduction do not contaminate solution A with Solution B as it will stop working. Working temperature of 20 degrees. You can place a dry negative in solution A but will need to watch the process carefully for between 1-4 minutes then transfer to solution B for about 5 minutes.

Potassium ferricyanide is a poison. Avoid contact with your skin and do not breathe the fumes.

Checking development times?

How do you know that the negatives you are looking at are correctly developed and not under or over exposed. The only way to be sure is to do a test. What follows is a method to help you achieve this:
   Choose a subject like a view or still life to take a series of photographs.
   First you will need to determine what the correct exposure should be.
   Then set the camera settings to two stops under and take the picture.
   Follow this by setting it to one stop under and take another picture.
   Now enter the correct exposure settings and press the shutter.
   Next, one stop over and two stops over respectively.
   Once you have done this wind the film on two frames and repeat the procedure, once done do the same again with a two frame separation so you now have three test strips.
Once back in the darkroom cut the film into three strips. Give the first section of film half the recommended development time the second set twice the time and the third group the suggested process time. Then compare the combined results of exposure and development and you will be able to clearly see which was developed correctly. It's worth the cost of a film to know that your films have been correctly developed.