Washing intermittently by using a small tank and agitating for a few minutes before changing it is more efficient by far than continuous flow washing. Studies have been done on this comparison. The reasoning goes as follows: suppose your wash tank holds 9x the volume of a piece of printing paper. After equilibrium has been reached, the water in the tank holds 9x as much of the solute as that in the paper. The next change of water reduces the amount in the paper to 1/9x1/9. after 4 changes, the aount remaining in the paper is about 1.5x10^-4. Ten time the volume of a piece of printing paper is a very small amount of water.
I remember one article in Photo Techniques that presented experiments where this method of washing was compared with continuous flow, but I don't remember when it was. There have been others, I'm sure.
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Gadget Gainer
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