Developer shelf life.

The keeping qualities of photographic chemicals to a degree is dependent on the dilution of the mix. In the first instance you should always follow the manufactures recommendation when mixing stock solutions by only adding the chemical to that quantity of water thus giving you a known starting point. If you require a more dilute working developer you should only make this up just before you are about to use it. Once used it should be discarded.

Reusable developers are poured back into their containers when finished with. Each time you pour it back a little bit is used up, it is a good idea to keep these containers full to stop the developer going off. This can be achieved in several ways if it is a plastic bottle you can squeeze the air out just before you nip the cap up, add glass marbles to the bottle so increasing its level, use a concertina bottle or the plastic bag out of a wine box ( if using one of these make sure it has been thoroughly cleaned.)

Remember that developer that has been used is likely to go off more quickly. It is a good idea to keep a record on each bottle of how many film or prints and what format has been developed. When you think you have reached the maximum usage discard it and make a fresh batch.

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.