Well I read 20-30 minutes for FB papers in Tim Rudman's 'Master Printing Course'. I've been following that procedure for a while, but now that I've a lot of printing to do and not so much time; I'm always looking for time quicker options. Plus it would be nice to save some water.
Ciaran
Ciaran, when I wrote that book almost 15 years ago in 1993 (published in 94) that was the received wisdom and a number of authorities at the time (including Kodak if I recall correctly so long ago) warned of dire problems if a full wash of that order was not carried out.
However, it was also the norm at that time to bleach fully, and often (especially with Kodak papers) this took quite a long time, allowing the bleach to penetrate deeply into the baryta layer and paper's fibres.
Since then I have pushed at the boundaries repeatedly and searched for signs of the predicted but never specified problems and never encountered any, although I tend to err on the side of caution.
My current practice when split toning/bleaching (as opposed to full bleaching) is to time the bleach according to test results and then shift the print swiftly into an adjacent half full sink and
hose it off as quickly as possible to move any bleach from the emulsion fast, as uneven toning can occur if the print is just put into water, which allows bleach to keep working - often unevenly.
I then wash until all signs of yellow have disappeared and then some more for safety, but as I am hosing during most of this time, washing off the bleach is fast and 5 minutes is usually sufficient for FB in my experience with light bleaching.
If I am bleaching longer or with a hard to clear bleach like dichromate, I will wash longer - much longer with dichromate.
I should add that I often bleach for sepia quite lightly, and with warmtone papers this can be less than a minute in quite dilute bleach, so there is not much chance for bleach to soak deeply into the fibres of the paper.
Tim