The less I need to use, the better. :)
There were some studies done on film washing in the 1950s. A 2% solution of sodium sulfite was found to reduce residual thiosulfite in film to zero in two minutes. Film bathed this way, followed by a running waster wash of one minute has less residual chemistry in it than would a sheet of film washed in water alone for more than an hour. This is the mechanism used for the various hypo clearing agents.
Washing efficiency can also be improved by first bathing films in seawater or solutions of common table salt at that strength for ten minutes before a thirty minute wash with running water. One reference in the literature states that a ten minute bath with seawater dropped the residual thiosulfate content to 0.005 milligrams per square inch where after thirty minutes of tapwater washing alone only lowered it to 0.080 mg/square inch.
My preference is to use a hypo-clearing agent for about eight minutes, rinse the film thoroughly twice and then do a very low trickle wash for 15 minutes.
if we use as much water as we can, ewe might end up with clean rivers again !
I've just joined today. I shoot 35mm with a Leica CL, Medium Format with a Mamiya C33 and Digital (gulp) with a Leica M8.
Just to add. I've always used the Ilford Method because I don't have running water in the darkroom.
Since I have a motorbase, I started to use the Ilford method too.
After twice a 2 min. neutral-to-alcalic fixer, 2 min. KHCA and then 5 times 2 min. washing (20°C +/- 2°C) with continuous agitation (motor base) to finish with 2 min ADOSTAB.
According to the Kodak Residual Silver Test, which is actually a 1+9 KRST solution,http://www.google.be/url?sa=t&rct=j&...zc_Ny619mPuJEw, and a Sodium Permanganate 1/1000 test to test the washing, it looks good, but I am absolutely aware that those tests are not conclusive, and good for my peace of mind, but better these than notting!
I process in King's Pyro-HD, which is superb, thank you Sandy!
BTW, is it true that Pyrocat processed negatives are less archival?
I go along with the "soak it out" policy. Preferable warm water but not hot enough to soften and damage the emulsion. I understand that if a bottle of even the most noxious liquid is emptied, refilled with water, left to sit, then emptied and refilled another 7 times, the result is clean water.
There's a test for residual hypo, but I don't know what it is. :(
how does using lots of wash water harm the environment?
There is a test for retained Silver Halides and a test for retained Hypo. Both should be used to establish whether your wash is up to the standards. Both are sold premixed by several chemical supply houses that specialize in photographic chemicals. I use the Photographers Formulary.
I use the "Ilford method" and presume that Ilford tested that method before publishing it. I haven't done any testing myself.
Test you washed product!