The 6 changes, 1:1000, numbers came from one of the film manufactures literature, though I forget which one. It has worked perfectly well for me over the years. The 30 seconds between changes Bill mentioned was required, though like him I always allowed a minute.
Note to Bill about the 3 rinses on the color film: Remember the stabilizer is the equivalent of hypo-clear.
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Dr E D F Williams wrote:
Six changes of 1 litre will dilute the first, say 1ml left on the film and reel, more than 1:10^6 times. In other words there will be less than a millionth or a ten millionth if you rinse the reel before starting the wash, of the original fixer solution left assuming that only 1 ml stays behind on the reel and film each time. But this does not account for the fixer that was bound to the emulsion. That removes itself by diffusion and takes about a minute (I think) and agitation prevents it diffusing back. I would say that ten changes of a litre every minute would be perfect, and it's what I do, and have half an hour ago just done.
-- graywolf http://graywolfphoto.com/graywolf.html
