There's more people in California now. When I was a kid in Sacramento 50 years ago, folks would water their lawns so much that it would flood the gutter and no one would think twice about it. Sacramento was fed by two rivers and water as plentiful. Now with people living here and we had 3 dry years and more agriculture, water is in short supply. There's more talk about using water more efficiently.
At one time a short alkaline bath was recommended by some companies as a post-fix treatment. Carbonate was recommended by Agfa for example. Metaborate has also been recommended. An alkaline pH means more swell, which can help speed washing. It could essentially undo the hardening action of alum hardener (in a typical hardening fixer), which is why the treatment was not recommended for alum-hardened prints. But this is a non-issue now (does anyone even use hardening fixers anymore?).
A sodium bicarbonate solution has a lower pH than carbonate or borates. The pH would likely be somewhere just above 8. Still alkaline but only mildly. And unless you give a thorough rinse before that, any residual acidic fixer might neutralize the weak bicarbonate alkalinity anyway. There was likely another reason for the bicarbonate recommendation. We'd have to get some chemist input. We know that even the properties of your tap water can have an effect on washing.
If you're using progressive trays of standing water, I might recommend short running water rinse between trays to get that "laminar layer" off before going into the next tray of fresh water.
The posts to which I referred above are probably findable. This use of sodium bicarbonate in wash water is after sulphite etc in the post fixing bath. It was found apparently that pure water was not as good at washing Fb papers as many tap waters, which obviously vary quite a bit. The use of bicarbonate was to emulate this effect. The quantity used is quite small compared to the sulphite content of HCA (300mg/L compared to 20g/L)
The posts to which I referred above are probably findable. This use of sodium bicarbonate in wash water is after sulphite etc in the post fixing bath. It was found apparently that pure water was not as good at washing Fb papers as many tap waters, which obviously vary quite a bit. The use of bicarbonate was to emulate this effect. The quantity used is quite small compared to the sulphite content of HCA (300mg/L compared to 20g/L)
...If you're using progressive trays of standing water, I might recommend short running water rinse between trays to get that "laminar layer" off before going into the next tray of fresh water.
When clearing platinum prints, this is SOP, and that 'laminar layer' is usually on my mind when handling film and paper in all processes.
Thanks -- my experience with gelatin and Sodium carbonate is with carbon prints. Once processed, a dark print can be put in a tray with a little Sodium carbonate in some hot water. It appears that this swells (softens?) the gelatin allowing it to release some of the carbon pigment and lighten the print. It works, but not well (for me -- others have found it more useful).
Thanks for all the great tips!
The Sacramento area received 1/4 inch of rain this morning. I was biking to work and ended up like a drowned rat, but we needed the rain. We also have a nasty fire burning in the mountains and I'm sure he helped a bit.
Years ago I hd my washing process tested. Five, one minute soaks following a 2 minute soak in 2% sodium sulfite and the prints were as clean as those washed in running water for one hour.
^^^ Also, was it FB paper, what weight, what brand? What water temp? Type of water... filtered, distilled, or tap? How much and what kind of minerals in the water?
Years ago I hd my washing process tested. Five, one minute soaks following a 2 minute soak in 2% sodium sulfite and the prints were as clean as those washed in running water for one hour.
Jim, was this fibre paper? Did you use ordinary "black and white" fixer which is somewhat acid or alkaline or neutral fixer which is reputed to wash out faster?