Hi there,
You didn’t mention what size of film that you are using. In general, I have observed with my students that tiny white pin-pricks tend to occur more often on roll film especially when the film has been wound on and then the camera was not used for some time (possibly dust settling over time when the camera is not being used). Back in the 1960s a German photographer (sorry it was too long ago for me to remember his name) wrote a book on achieving the highest quality with Leica cameras. His advice was to only wind the film on when you are ready to take the photograph. His argument was that the film was ‘protected’ in the cassette and moving it ‘fresh’ immediately prior to taking the picture reduced the risk of dust settling on the film. Whether this is true I do not know but I have always followed this advice (not winding on film until ready to make the photograph) and have never had any significant issues with tiny white pin-pricks irrespective of the format that I was using at the time.
On the more general theme of using a pre-wash/pre-soak, if you do a search on Photrio you will find thousands of comments for and against using a pre-wash/pre-soak. In fact, some of the exchanges have got really heated in the past!
I personally have always used a pre-soak irrespective of developer or film. I have also always taught my student to use a pre-soak and I have never had any issue with it causing any problem whatsoever. I know plenty of photographers who happily do not use a pre-soak. However, whenever someone comes to me with a problem with uneven processing (mostly with 35mm films) the introduction of a pre-soak has eliminated the problem every single time.
Another reason that I use a pre-soak is that, for my photography, I have been exclusively using a two-bath developer for more than 15 years. The reason being is that the two-bath developer is reused for 15 films and the pre-soak stops the Bath A from becoming very discoloured by the dyes that are now present in all modern films.
Finally, to your original questions:
- Tap water is fine for a pre-soak but, depending upon your local water supply, you may have to filter it to remove any impurities in the water
- You should pre-soak a film for at least two minutes
- The agitation that you use should reflect the agitation that you use for development. So, in my case, that is 4 inversions in the first 30 seconds (followed by a sharp tap to the bottom of the tank to remove any air bells) and thereafter one inversion every 30 seconds (also followed by a sharp tap to the bottom of the tank).
Best of luck with you experimenting,
David.
Note: my current temporary website address is :
http://dsallen.carpentier-galerie.de