Black and white film photography is still popular around the world and new generations of amateurs and professionals are learning the black art of film development, albeit with a greatly reduced range of commercial products. Those of us who started processing our own films in the mid-1950s will have been surprised over the years as the advice on washing films after fixing changed. We were brought up in the wash the film in running water for 30 minutes school. However, the success of our fixing and washing methods is evident. None my negatives from that time has deteriorated.
...washing for 30 minutes is necessary in order to remove all trace of fixer and soluble silver. If this is not done, the negatives will deteriorate, and processes such as reduction and intensification become hazardous.
Simply placing the tank under a running tap seldom gives a steady change of water round the whole film; indeed the inner coils towards the base are barely affected. Unless you are prepared to empty the tank completely (removing the lid) and refill with fresh water at least 8-10 times during the 30 minute period, with regular agitation, the tap-water must be led into the centre hole by a length of hose acting like an inverted fountain through all the coils of the film. Washing is carried out in this manner by the Polly film washer, a neat little device which is available for use with up to six tanks at once by means of simple adapters.
Note carefully the temperature of the wash water, especially at the start. Any sudden change in it subjects the gelatin emulsion to great strain, and it is then apt to split into minute cracks. This is known as ‘reticulation’, for which there is no cure; so, if it is not possible to have running wash water at 65-70°F, gradually reduce the working temperature by several successive changes, each two or three degrees cooler until it is the same as the tap water. If this is below 60°F, washing time must be increased by 10-15 minutes, but avoid the necessity if you can.
|An illustration from The Complete Photobook by Philip Johnson,|
Fountain Press, 1955
When your films “go wrong” after drying and storage, it is mostly not, as so often supposed, from insufficient washing, but from imperfect fixation. After fixing wash for five minutes in running water, then harden, and back to running water; five minutes in this is ample.
|From Ilford Technical Information. Rapid Fixer.|
Harman Technology Ltd. July 2010
However, diffusion is involved. Diffusion in a gelatin emulsion is much slower than in water. The rate of diffusion out of the emulsion depends on the difference in concentrations of the silver-hypo complexes and the free hypo in the emulsion and the concentrations in the surrounding water. Therefore, the more often the washing water surrounding the emulsion is replaced, the faster will be the rate of diffusion. Agitation is important because it replaces the water into which silver-hypo complexes and free hypo have diffused from the emulsion by water containing a lower concentration. In processing films, the purpose of agitation is to prevent the formation of what physiologists call unstirred layers and physicists call boundary layers at the emulsion surface both to let fresh developer, fixer — and water for washing — reach the emulsion and its inner structure.
In my opinion the photographers community has developed over the years a false but very obsessive position according to which a proper washing cannot be achieved without leaving the film plenty of time under a waterfall. And even the reasonable common suggestion of washing the films for about a quarter of an hour under a running flow which allows a complete change of water in the tank every five minutes (Kodak washing procedure) is a waste of water compared to Ilford's method, because this 5' change rate requires a water flow of at least 1.5 l/min for a 500 ml tank (we measured this by monitoring over time the decrease in concentration of a conductivity tracer introduced in the tank at the beginning of the wash). It was a therefore a pleasure to read Suessbrich's paper, which I hope will help to break all these generally accepted but preconceived ideas about washing.