The Thermometer.

This is one of the most important pieces of kit in the darkroom. As already mentioned temperature is one of the main controlling factors in the processing of your films and prints. It is important that you have good quality thermometers that are graduated to at least half a degree but a quarter of a degree is better and one that has a thicker line at the vital 20 degrees C. It is a good idea to have a thermometer for each of the chemicals you use in the processing of your films and prints as it will stop cross contamination.Also there will be no hold ups if you break one. It is recommended that you keep to one type, preferably alcohol as it is safer than mercury. If a mercury thermometer breaks it will contaminate the chemicals it comes into contact with and fog any prints that are being processed at the time.

What temperature?

20 degrees centigrade is the standard temperature that film development should be carried out at. It is also important that this temperature be maintained throughout the process. You may use a higher or lower temperature which will shorten or lengthen the development time. There is a risk that the negatives may not be fully developed; you should wherever possible follow the instructions as to time and temperature unless an alternative has been suggested by those instructions. With experience you will know what temperature and time combinations give good results. I personally always develop my film at 20 degrees C unless a higher or lower temperature is recommended.

Over development

The film has been processed for longer than it needed. The following can cause this:

• Too long a development time.
• Too high a temperture. ( thermometers can go wrong.)
• Too much agitation.

Attention to these factors should avoid this. If you know that a film has been under exposed then you can remmedy it by over developing.

What does developer do?

The function of the developer is to bring out the latent image held in the emulsion. This is achieved by a chemical reaction, acting on the silver, producing dark areas where it is light and bright areas where there is shadow. The negative is reversed later with the print. The two most important things to keep at the front of your mind are: the development time and the temperature. It is these two factors that ensure the ultimate image quality you later produce in the print. Too short a development time will produce too thin a negative, like wise too long a process time will make the negative too dence, leading to very short and very long print times.