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.
