Any real advantage to pre-soaking HP5 to remove the anti-halation layer

[stradibarrius]

I am curious if there is an advantage to pre-soaking HP5 to be developed in Rodinal???

[Robert Kalman]

Not sure about HP5 specifically, but I always pre-soak my Tri-x because I believe that the developer then spreads more evenly across the film when immersed into the developer.

[Bill McMannis]

As Robert says, pre-soaking Tri-X (and TMax) makes a huge difference. While I have not shot HP5 if or when I do, I will presoak.

[Eric Rose]

Yes you must pre-soak! If you don't you will become a darkroom outcast. No one will want to play with anymore. Seriously I have done it both ways and have not seen any real difference in neg quality. If I plan on reusing the developer I will pre-soak so as to not muck up the soup.

[rich815]

Supposedly Ilford's data sheets say: "A pre-rinse is not recommended as it can lead to uneven processing."

And some people say its best to pre-soak or you'll get uneven processing.

Both are probably right.

[rich815]

Not sure about HP5 specifically, but I always pre-soak my Tri-x because I believe that the developer then spreads more evenly across the film when immersed into the developer.

Sounds like that makes sense. But then I've seen it said that not presoaking is better because then the dry film absorbs the developer better and faster than film that is already saturated with water.

I'm not trying to be flippant, these are all things I've read in the debate. To be honest I think either is fine as long as you're consistent.

[Kevin Crisp]

Makes a 'huge difference' how? And why? I know this as taken as gospel, but I don't understand why. And I've never pre-soaked any sheet film and I've never had uneven development either, despite short summer development times and tray development.

When I put a sheet of film into a tray, the entire sheet is submerged in a lot less than 2 seconds. Assuming 2 seconds, however, then the differential in development time across the sheet would be, in the context of a 5.5M development time, about 0.6%. So you have a theoretical increased density resulting from 0.6% more time in some random pattern across the sheet of film. You are never going to notice or detect that, any more than you would if you left half a sheet in the developer for just 2 seconds longer than the other half.

If the theory is that pre-wetting the emulsion makes it wet faster in the actual developer -- the most common explanation for a pre-soak -- I still don't follow the reasoning. There is going be a slight delay, wet or dry, in the developer reaching the emulsion in all places. There is the hair splitting tiny difference in developing time, again. You've got the same 'problem' you are trying to avoid. If it takes, let's say, a second or two for dry emulsion to be 'wet' by the developer, the process across the sheet is still going to be uneven in the very slightest way, true enough. But since the whole sheet is marching toward being wet and developed with the differential from place to place on the sheet being the same plus or minus one or two seconds, the difference is never going to be observed.

It is true, of course, that uneven development can be theoretically more likely to occur as development times get shorter and shorter. That 2 second delay in fully wetting the dry film and getting it on its way to an image because proportionally larger as the development time gets shorter. But even with a smoking short development time of 3 minutes, the delay is still only 1% of a difference, in a random pattern across the sheet of film.

If dry emulsion were resistant to wetting, and inconsistently so, so that the top of a sheet of film might take 10 seconds to get wet and get actively developing, while the bottom or sides would taken much shorter or longer, then I could understand how just getting the film wet in advance would even out the process. But dry emulsion doesn't interact with liquid that way. Put a drop of water on emulsion and wipe it away a second later. The film is wet. And it doesn't matter where on the sheet you put that drop, the film is going to get wet just as fast. And if instead of water that drop has developer in it, the chemical activity is going to start quickly.

[cyrus]

I've read that presoaking actually does NOT help the developer spread evenly, and instead makes it harder for the developer to soak into the emulsion since the preexisting water has to be displaced. I don't know if anyone has scientifically tested any of this (Ctein?) but I tend to presoak to rinse off any dust, but mainly because that's just how I was taught

[Jason Greenberg Motamedi]

I am a bit agnostic when it comes to prewash, but it does help bring your film and developing tank to temperature.

[Michael Graves]

I'm no scientist and I didn't do any controlled tests. But I do know that before I was told to start presoaking my film, I consistently had problems with consistency in even tones, such as skies and such. After I started presoaking, those problems are so infrequent that I can't remember the last time it happened. Go ahead and tell me the presoaking has nothing to do with it. But I'll keep doing it anyway.