When using a standard 16 ounce two reel developing tank, Kodak's method of running water used with HCA, requires a minimum flow rate of .2 gallons per minute, using a total volume of 1.125 gallons after 5 minutes. The alternative of 10 fill and dumps uses 1.25 gallons. Ilford's method uses a volume of .375 gallons, but assumes a non-hardening fixer. Kodak assumes a hardening fixer and would require less washing than their published data if adjusted for a non-hardening one, especially if still used in conjunction with HCA.
Very good points Greg. And, good measurements of the water.
These values would be reduced yet again by an alkaline fixer.
You may want to keep the film for 5 years or so, and re-examine these results. I have done so with paper and the results are astounding. The "bad" ones that tested as unwashed are dark brown!
What levels does the Kodak test indicate as far as remaining thiosulphates goes?
According to the data sheet that came with the Hypo Estimator:
Density of Stain vs. Estimated Grams of Thiosulfate Ion/sq. meter
Very well presented. In fact better than I have ever seen in any book I have read on the water washing part of film processing. All of us on APUG owe you a debt of gratitude for this comprehensive test. I use the Ilford method but extend it to an initial flush then 5,10,15,20, 15,10 5 so 8 changes in total. I'll now stick with this as my method.
Thank you, Pentaxuser and Ron. The whole purpose of the project was as a teaching aid in class, as well as to stop the arguing here since nobody else was willing to actually put these methods to the test instead of arguing which was best simply because they used that particular method. I am not going to draw any other conclusion from this comparison except to say that if anyone uses the combination of hardening/nonhardening fixer, HCA, and wash methods that the manufacturers recommend, you can't go wrong.
Thanks for the altruistic work.
The results should stick somewhere before time buries this thread under the new ones.
I would say that your test shows that both methods work quite well with non hardening fixer, after that it comes down to what you prefer, or what fits your needs at the time.
The Ilford method might save water, but there are times that running water over the film gives you a chance to duck out and do whatever, like find a towel, while the film washes on autopilot.
We could ask the moderators to make this a sticky.
Thanks very much, Greg. I'm always wondering if I have washed enough. No more.