Presoak - I never used it (going on 50 years now), but lately I do more semi stand development in Rodinal (agitate every 4 minutes). I believe presoak was recommended by Sandy King for stand and semistand with Pyrocat, and so I do also with Rodinal, for initial chem contact.
Unnecessary?
The pre-soak has a few potential benefits:
1. Since pre-soaking lengthens the development time, and short development times (<4 min) can cause uneven development, pre-soaking can provide a more even development with short development times.
2. Temperature conditioning for tank, spool and film.
but it also has a few potential dangers or disadvantages:
1. Pre-soaking must be long enough (several minutes) or it can cause uneven development. The reason for this is again that pre-soaked emulsions need longer development times. If pre-soaking was not full and entirely even, development won't be either. You can test this by putting a drop of water on the dry film for a minute or two. After development, you will clearly see where that drop of water had been. The area will be slightly less developed than the rest of the film.
2. Pre-soaking adds a step to the process and extends the processing time. With sufficiently long enough development times, this is unnecessary.
and there are also a few myths:
1. Pre-soaking washes the anti-halation dye out of the emulsion and this improves development!
As far as I know, the anti-halation dye does no harm to the development process. Conversely, the pre-soak might wash out some built-in development agents, helpful and intended to be there for the process, in which case, pre-soaking becomes a disadvantage.
In conclusion my recommendation is:
1. Only pre-soak if the film manufacturer recommends it, or if your development process pushes you below 4 minutes.
2. If you pre-soak, do it for at least 3-5 minutes or you'll risk uneven development.
3. If you want to pre-soak, don't forget to add it also to your film development test, because the development time lengthens with the pre-soak.
