I just downloaded "Processing B&W Paper" pdf from the
Ilford site and noticed a possible discrepancy. On page 3,
top left, it says to wash for 20 minutes.
But then further down the page under the "optimim pernance
sequence", it says to wash for 5 minutes.
Both times are mentioned after using their washaid.
Five minutes sounds awfully short.
So is 20 minutes the correct time?
Current PDFs, fixers, papers, the one you mention, offer
a few post fix wash routines. The most recent, the fixer
PDFs, suggest the 5-10-5 minute wash, hca, wash
routine what ever the paper's fix routine.
The routine you mention is the 5-10-20 minute wash,
hca, wash. Should be OK. In my mind the shorter 5-10-5
routine has one hovering over the tray/trays with no or
little time for other matters.
The "optimum permanance sequence" or something to
that effect is, in the latest PDFs, associated with and
only with a low maximum silver level of 0.5 grams
per liter working strength fix.
Used to be an Ilford " Archival Processing Sequence".
No longer. The sequence was a very short fix in film
strength fixer followed by the 5-10-5 wash, hca,
wash. That 5-10-5 routine persists and is still
one of Ilford's suggested wash routines.
Ilford no longer uses the word archival. But for
Optimal keep your silver levels low. For that and
great mileage from the chemistry they suggest
the two bath fix.
I manage an archival fix and great chemical mileage
using a single bath of very dilute one shot fixer. Works
well with my single tray processing method. A single
tray for processing is a big space saver. Dan