Washing Film - Best Environmentally Friendly Way to Do It?

[ozphoto]

As a latecomer to all this discussion, can I address the original OP? I also live in South Australia (known as the Driest State in the Driest Continent on Earth) and I've likewise struggled with my conscience as I contemplate building a darkroom in the next few months. The solution I've decided on, which may be of some use to you, perhaps, is to dedicate one of our rainwater tanks as my photography water supply. (I'll install appropriate filters). If it runs out in mid summer, that'll be a good time to go and shoot some more film until it rains again, or -GASP! - drag out the DSLR.

I have been using rainwater to do just that; my main objective for the original question, was how to best use any/all water I had access to regardless of it being mains, or rainwater from the tank.

The less I need to use, the better.

[Tom S.]

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.

[RalphLambrecht]

if we use as much water as we can, ewe might end up with clean rivers again !