Pre-soaking FB paper?
Exactly. I don't do it for paper, see no reason for it and in fact never heard of it until now. But I generally do pre-soak film for a couple of reasons. One is the tempering mentioned. The other is with rotary processing in my Jobo. Jobo recommended a pre-soak because they found that with most film developer combinations the slowing of development times for a 5 minute pre-soak just about exactly offsets the increased activity from the continuous agitation. This was recommended in the Journal of Rotary Processing and I have found it to be generally true, allowing me to use the same starting times with the Jobo as for inversion. It certainly does no harm.
Originally Posted by Michael R 1974
I do not use it with Diafine in tanks as the manufacturer specifically recommends against it. Though I haven't tried going against that recommendation it makes sense to me.