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Pre-soak before developing & developer reuse question

Anon Ymous said:
Yes, dilution is an option, but I don't understand how I can alter pH...
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When mixing your own developer, you have control over the type and amount of activator in you developer. To reduce the pH for example (less pH = less development activity) you can use a less active activator (borax instead of sodium carbonate) or use less of it to get the solution's pH down.
 

Before saying anything else, I'd like to stress that I'm not an expert in this field.

Anyway, some people may say that you need to increase development time if you presoak, some may say that you don't need to etc... I've only done one test, but I can't say that it's ideal, or correct, or whatever. So, I took a film leader and immersed the wide part of it in water. The narrow was left out. Then I developed the leader in print developer. Development wasn't uniform and the part that was darker after about a minute was the soaked part. The difference between the two parts seemed to decrease as time passed, but it was still noticeable. The problem with this test is that print developers are generally much stronger than film developers, so if development rate is affected by presoak and wet parts get a head start, it will give exaggerated results. If film developer was used the difference might have been minimal, or practically unnoticeable, as the dry part would sooner or later become as wet as the wet part. Honestly, I haven't done any serious tests to be able to back any statements. It is interesting though that PE says that (there was a url link here which no longer exists).


Oh, now I got it, but I don't mix developers (yet). And I'd rather mix paper developers when I start home brewing. You see, we have very few choices for paper developers here, as opposed to film developers. I can find nearly every film developer from Ilford - Kodak.
 
Anon Ymous said:
...Anyway, some people may say that you need to increase development time if you presoak, some may say that you don't need to etc...
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In very simple terms:

The developer needs to get to the exposed silver halides, deeply imbedded into the gelatin emulsion, in order to 'develop' them into metallic silver. If the film is dry, the developer solution itself will take care of emulsion swelling, and in that case, is right there to start the developing process. If the film was pre-soaked in water, the emulsion has already absorbed a liquid (water) and this needs to diffuse out and be replaced by developer before the developer can start the process.

Consequently, a pre-soak will delay the development and the process will take a bit longer. This is not a bad thing, actually it can be useful (to extend otherwise very short development times), but it needs to be considered when switching between pre-soak and no pre-soak.
 
RalphLambrecht said:
Mahler

I'm about 3 years away from Florida retirement, so, this is important to me! Why not calibrate the system to 25C?
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I have Ralph! 24C on the Jobo....everything works very well, and is calibrated perfectly.

As you desire, PM me about places to live here...you are always welcome to come by....I have lots of information for you.
 

Hmmm..... (rubbing my bearded chin deeeeeeeep in thought)...... you have a point there Ralph!
 

Having said that, the effect of a pre-soak on development time is easily tested for. Next time, start your film with some uniform middle-gray exposed frames. Just prior to development, and in the dark, place a drop of water to one of those frames and blot it off after a minute or two. Then develop normally. After processing inspect the frame and you will usually see a slightly lighter spot where the drop 'pre-soaked' the emulsion, proving that a pre-soak reduces the developer activity.

Again, this is not necessarily a bad thing, but it needs to be accounted for. Use a pre-soak if your process benefits from it, mine does not.
 
Anon Ymous said:
It is interesting though that PE says that (there was a url link here which no longer exists).
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There's an article where this was tested on another site and it showed quite conclusively that adding a pre-soak leads to lower densities, all else being equal, so a slight reduction in overall development. Of course this can easily be compensated for.

Ian
 
I always pre-soak for about 3 minutes in two changes of water. One reason is for temperature control. The other reason is because I occasionally used to get air bells with 120 film. Pre-soaking solved that problem and I'm quite happy with my negatives now.
 
Anon Ymous said:
Ralph, that might be true and sounds reasonable, but why did the exact opposite happen in my test?
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I really don't know. Maybe, with your test conditions, the time to diffuse was shorter then the time required for your developer to swell the emulsion.

Try the test described in post #32. In your case, the spot on the negative should be darker than it's surroundings. In my tests, it was always the other way around.
 
If you place a drop of water on film and then place the film on a reel, you have the risk of evaporative cooling and a number of other things that could go on. For example, blotting is not the same as draining a tank of water. It compresses the swollen gelatin.

In any event, I have seen no difference between prewet and no prewet in color and B&W film processing. OTOH, I have seen an increase in small defects and less contrast in both processes with no prewet. Going back to the earliest Kodak booklets on film development, I have found instructions that include a prewet with tray development of B&W films.

It really does not matter. What matters is what works for you, not me or someone else.

BTW, the swell argument falls down when you consider that diffusion of the large development molecules are involved. As dry gelatin swells, it must achieve a maximum value before developing agent diffuses, but it does not need to meet that value to allow diffusion of OH ions (alkali). The Sulfite and halide ions are inbetween. So, development is different with prewet film than it is with dry film, in the sense that the rate of diffusion of the different ingredients enter into this.

Imagine a dry sponge immersed in water with small particles of varying size suspended in the water. These small particles begin diffusing inward as the sponge expands, but each particle will diffuse according to its size. That is the best analogy I can give. Timing of these is important in instant products, and so the diffusion and swell have been extensively studied and there are many many internal reports on this at EK.

PE
 
Photo Engineer said:
If you place a drop of water on film and then place the film on a reel, you have the risk of evaporative cooling and a number of other things that could go on...
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You've got a point about the cooling effect due to evaporation, but 'significant' evaporations only starts after blotting, and it ends as soon as the film goes into the developer, which is a very short period of time in the proposed test, and that followed by 10 minutes of development (in my case) hardly makes for a cooling effect to worry about.

Photo Engineer said:
...In any event, I have seen no difference between prewet and no prewet in color and B&W film processing....
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I have. I really have, anywhere between 5 and 10% of development time. Enough to include it into a proper film test for the discerning practitioner.


The fact remains, active development agents must get to the exposed silver halides to do their work. If pre-soak water is 'in the way', it has to be removed, diffused, saturated or else, and this will slow things down, unless it takes more time for the developer to swell the emulsion itself.
 
Shoot less film. Seriously. Or take a break from film, try digital, and return to film. or try shooting 4x5 film. The more expensive it is, the more you treasure it, the more you weed out bad images before you take them.

Or buy bulk developer.
 
tiberiustibz said:
Shoot less film. Seriously. Or take a break from film, try digital, and return to film. or try shooting 4x5 film. The more expensive it is, the more you treasure it, the more you weed out bad images before you take them.

Or buy bulk developer.
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I must have missed something!
 
Ralph;

Let me explain it another way....

If film is fully swollen with plain water, and then dipped into acid or base solution, then you can measure the pH change instantly at the bottom of the film near the base. Other ingredients can be shown to arrive later. Diffusion of H+ and OH- are nearly instantaneous. If you do the same thing with dry film, the diffusion front of liquid can be seen advancing and wetting the base side of the emulsion if you view it from the back. In this case, both swell and diffusion take 15" or less depending on thickness so acid and base fronts and developing agents diffuse more nearly together.

Equillibrium of the developer salts in a wetted film takes about 15" for the remainder to catch up.

Therefore, both unwetted and wetted film take about 15" max at 68F (20C) to fully spread through the emulsion. This is as nearly a photo finish (pun intended) as you could ever desire! And, the timing just about cancels out. Now, this can be offset by very hard water and water with a very alkaline or acidic pH, and it can also be affected by a number of other things, but on-average things equal either way and the prewet serves to temper things at high temps and to reduce defects.

Just MHO.

To describe one test, a film is dyed with an insoluble indicator dye and then treated with acid or base and the delta density vs time is measured. When the known Dmax is achieved by full pH change, then equillibrium has been reached. This can also be done for reflective materials. You can measure the change in color with time and you can also take cross sections and place them on a microscope and add a drop of acid or base under the slide cover and observe the wavefront of dye change and time it. The same thing can be done with developer to time the appearance of silver and the rate at which it develops in a front through the coating.

BTW, the person who taught me this was Milan Dvorak, nephew of the composer of the same last name. He was one of Kodak's prime experts in photomicography. I was a dud!

PE
 
Wow, a lot of good info here. I never expected so many replies. Anyway, thanks everyone...I'm off to try to digest all the info you gave
 
i pre soak except for the short time when i used to use xtol developer and it was recommended by kodak not to pre soak.
i usually soak and agitate for a few minutes, shake the bubbles off &C when i am using 35mm o r120 film.
if i am using sheet film too. it helps me get the sheets ready to go in the developer
and allows me to separate the sheets and count them ahead of time and make sure nothing is stuck together ...

whether it is a necessary step or a waste of time, ive been doing it for a long time, and i really don't see any reason to stop ...
 
PE

I really don't know how I would measure the pH at the bottom of the emulsion, so I have to take your word for it, but the drop test clearly shows reduced development fort pre-soaked film. To avoid the influence of evaporation cooling, we can repeat the test with water drops slightly elevated in temperature or partially pre-soak film in a bath in which the pre-soak area can be fully submerged. But first, I will try to measure evaporation cooling on larger drops.
 
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