REPLENISHMENT SYSTEMS
Continuous Replenishments
In these instances, the replenisher is flowed into the tank at a constant rate dependant on the speed of the processor for as long as film is being processed.
Flow-raters or flow meters with a small glass or plastic ball that rises in a graduated glass tube are used to estimate the flow.
The replenisher solution either is pumped or flows by gravity through the meter into the recirculation system of the process solution. In this instance, there is a continuous overflow of solution in order to maintain the tank level constant.
An alternative and more modern system uses a time switch on a metering pump that switches on for a fixed period every so often, or a cam that switches a gravity feed on periodically. This method makes adjustments between different film gauges and different film stocks more easily automated.
Batch Replenishment
This method was used for stills processing or for replenishing the early solutions that processed or tinted film on racks or frames.
After each process a quantity of solution, depending on the amount of film processed, was removed and replaced with replenisher.
A different formulation is needed from the continuous method above.
Calculation of Replenishment Rates
The most accurate method of determining the replenisher formula and replenishment rate [i.e. the volume needed for every 100 ft, say, of film] consists of analysing a solution for the individual chemical components, processing a relatively large quantity of film and then re-analysing the solution.
From this it is possible to estimate the quantity of each chemical required in the Replenisher to return the solution to standard and the volume of replenisher solution required per foot or metre of film. If analysis equipment is not available, standard replenisher formulae and rates are available from the film manufacturer and it is then possible to adjust according to the sensitometric results obtained.
Almost all processes used in the world today were devised by Eastman Kodak. Other manufacturers make their film to fit these processes.
Some Kodak process and replenisher solutions are available a pre-packaged kit form, both from Kodak and from other suppliers.
Leader rates
When running leader, the blank film that is used to "lead" film through the processor no chemical action is taking place.
The chemistry is not being used, but there is always some carryover of solution from tank to tank on the film surfaces, so a low level of replenishment is operated just to maintain the solution levels.
This flow rate for leader film is the Leader Rate.