They maybe a waste of time for you but not others including me. However in the future I will feel free to waste as much of your time as I can.
Never pre-soaked and never will. A complete waste of time.
[Warning: Pedantic Post]
I work in reservoir engineering with a specialty in modeling fluid flow through porous media (primarily water and water-based solutions through geologic reservoirs). That's not a perfect analog to the film world, but probably close enough to take a shot at this question, which I've given some thought to in the past.
To my thinking, there are at least two mass-transport-related processes going on here that dictate how quickly the developer starts to react with the latent image in the emulsion. The first is the ability of the developer solution to penetrate through the outer layers coating the emulsion (e.g., the protective topcoat, the film base, etc.). The second is the ability of the developer solution to diffuse into and throughout the emulsion.
Most people make the quite reasonable assumption that since the pre-soak water and developer solution are perfectly miscible (i.e., both based on water), doing a pre-soak should make the development happen faster -- almost as if the pre-soak water were helping to "escort" the developer into the film faster. I think that assumption might be applicably true to process #1 above, depending on the composition of the various outer layers (I don't know for sure, but it seems at least plausible). This phenomenon, if real, might be comparable to the positive correlation we always see between phase saturation and relative permeability in porous media.
The movement of the developer into the emulsion (process #2 above), however, is a bit more complicated. Similar to what was described above for the outer layers, doing a pre-soak might speed up the process of distributing some of the developing agent throughout the emulsion layer (again, I can't say for sure), but there's a catch: The pre-soak water in the emulsion is also diluting the incoming developer solution. And that's really the problem here -- dilution. It's not so much that the developer solution is having a hard time "pushing" the pre-soak water out of the way -- after all, what we're describing is a purely passive transport process in which both fluids exhibit perfect miscibility. Instead, what's going on is that the two fluids are mixing for a period of time until the fluid in the emulsion is more or less compositionally identical to the fluid in the rest of the tank. That process is entirely based on diffusion, which in general is quite slow, especially through semi-permeable membranes. Pretty much the only things you can do to speed up the process are: 1) agitate frequently at the beginning of development (thereby maintaining the steepest possible diffusion gradient at the fluid-film interface); and 2) develop at a higher temperature (since the rate of diffusion is moderately positively correlated with temperature).
So, we have two competing effects: a) the possibility that wet/swollen layers might slightly speed up development by aiding in the movement of water molecules through the various layers; and b) the absolute certainty that the in-situ pre-soak water in the emulsion will slow down development by temporarily diluting the incoming developer. Based on my lab experience testing diffusion-limited processes, my instinct is that the second process is likely more significant than the first. So, there probably is something to the idea that a pre-soak should be compensated for by slightly extending the development time. The only way to know for sure would be to run a test with a densitometer. I might give this a go to satisfy my own curiosity.
There's an additional effect to consider, and this comes from an analogy to paper chromatography.
First I need to explain what happens in paper chromatography. Here's how it works. a small amount of sample is applied to a strip of paper in the form of a spot. The spot is applied near one end of the paper but not quite at the end. That same end is then dipped into and held in contact with a solvent. (The solvent could be water for example.) The solvent (assume it's water) creeps up the paper by capillary action. As the water rises it carries the sample with it. Typically the sample does not travel at the same rate as the solvent front, but it does move up the paper. (Different components of the sample travel at different rates.) This is not happening by diffusion but rather is a more active form of transport. Diffusion does occur, but diffusion is the what is responsible for the the movement of the spot. (Diffusion produces spreading of the spot, not movement of the center of mass of the spot.)
There are some differences between paper chromatography and the application of developer to film, but there must be an important similarity as well, which is that as the water penetrates into the gelatin it will carry developer along with it. As with paper chromatography this is not a diffusion effect but is a more active form of transport. This active form of transport does not occur if the gelatin is first hydrated before the developing solution is applied. In that case (the pre-soak case) transport of developer into the film relies on diffusion, not the more active form of transport that I am discussing here.
The bottom line is that, although there are several effects taking place, some of them perhaps competing with the effect I described here, the effect I am describing will tend to slow down development if the film is pre-soaked.
This is probably a transient effect. Once the system approaches something closer to a steady state then this delaying effect does not effect further development. This probably means that the effect would best be considered in terms of a more or less fixed delay i.e. a simple addition of a certain amount of time to the development time rather than a proportional adjustment is probably more accurate.
I'm not actually sure if people usually recommend a fixed-time adjustment or a proportional adjustment, but at least some have recommended that a pre-soak compensates for rotary vs. conventional film processing, which sounds a lot like a proportional adjustment to me. However, I think a fix-time adjustment is probably more appropriate.
If a fixed time adjustment is most appropriate then what time would that be? I will hazard a guess, a rather wild guess. Suppose that normal development averages about 5 minutes. Suppose that one assumes that 15% greater development gives a reasonable adjustment for a 5 minute development time if one uses pre-soak. (This 15% is just a wild guess.) That would mean adding 45 seconds to the development time. If my hypothesis is more or less right then adding 45 seconds would apply regardless of the total development time. One probably just round that off to one minute.
So, what if one were to convert a conventional processing time without presoak to a rotary process with a presoak. The following scheme might be a reasonable first guess on how to do the conversion. Take the conventional processing time. Add one minute. Then multiply by 0.85. I'll bet that would get you fairly close most of the time.
Note: After I wrote this I saw the latest post by M Carter which recommended adding one minute to the development time if one uses pre-soak. That sort of confirms my wild guess. I think M Carter is also on the money when he or she says that a short pre-soak is not a good idea. I think you want to either reach more or less full hydration of the film (i.e. a reasonably long pre-soak) or not at all. Otherwise the process becomes less controllable.
Just be wary of short pre soaks. Myself and others have found that (at least with Delta 100 in 4x5) a short pre-soak is disastrous. When the film dries, a weird crack pattern emerges on the base side, but it does render the negs useless. It took me a fair amount of testing to nail this down to a 1-minute pre soak causing this issue. I did find a post or two about it on other forums as well.
That's really interesting. I was getting the exact same thing -- a crack-like texture on the non-emulsion side -- in 4x5 and 8x10 sheets of Delta 100 developed in Pyrocat-HD. It's suggested that development in Pyrocat-HD should be preceded by a water pre-soak (1-2 minutes), which is what I had been doing. When I eliminated the pre-soak, the cracks went away, too. The problem, however, is that not doing the pre-soak often (~50% of the time, in my case) results in mottled, uneven development along the edges of the sheets. I eventually gave up on Pyrocat-HD for those reasons and went to XT-3. It's unfortunate, because Pyrocat gives really beautiful negatives with fine grain and high sharpness. That said, XT-3 is a close second.
Just be wary of short pre soaks. Myself and others have found that (at least with Delta 100 in 4x5) a short pre-soak is disastrous. When the film dries, a weird crack pattern emerges on the base side, but it does render the negs useless. It took me a fair amount of testing to nail this down to a 1-minute pre soak causing this issue. I did find a post or two about it on other forums as well.
And it could be part marketing/customer service. Short pre-soaks are not safe (as per others above) and not needed for average use...so to reduce complaints from inpatient and sloppy workers, it is better not to recommend it. But Ilford stops short of saying it is actuall harmful, since pre-soaking can be useful in the hands of the experienced worker.
Was the presoak water the same temperature as the developer, rinse water, fixer and wash water?
What conclusion did you come to about the short but unspecified soak time that resulted in a weird crack pattern on the base side when it is dry?
Was this the case with all films and all developers in your testing?
...........
It's quite possible that you'll only see this anomaly if you're developing in a tank where the film holder or the tank, itself, makes direct contact with the film and inhibits the even flow and penetration of the pre-soak water. If you're developing roll film on reels, I'd be willing to bet you won't see it.
This puzzles me. I have always thought of the back of the film as being inert but it seems not so. Is it the case that you've found that a short water pre soak causes this problem with one rather dilute, high pH developer, Pyrocat-HD, but not with a more concentrated, lower pH one? Or do you not do a presoak with the XT-3?
If you ingress emulsion with water, it has to depart to accept developer and it may not do that evenly.
As a follow-up to my previous post (#33, above), I ran some film tests over the last few days to evaluate what impact, if any, doing a water pre-soak has on development, and the results really surprised me. This is a pretty long post, so if you prefer not to read the whole thing, the primary takeaway is this: Doing a water pre-soak does inhibit development (i.e., reduces negative density), at least for the combination of film, developer, and process type that I tested (Tmax 100, Adox XT-3, rotary development). I was really surprised at just how significant the effect is. I describe the testing procedure and results in detail below.
To run the test, I exposed six 4x5 sheets of Tmax 100 with a 21-step Stouffer step wedge, developed them using different development routines, and measured their resulting densities with a densitometer. Plotting the results (zone versus visual density) allowed me to visualize how the density ranges compared among the different development routines.
For each exposure, the step wedge was placed on top of the film in a film holder. Following that, a photograph of a flat, uniform surface (e.g., a white wall) was made with the camera and lens under daylight to create a film negative of the step wedge. The step wedge allowed me to record a range of densities in half-stop increments on the film, ranging from what is essentially equivalent to a Zone 0 exposure all the way up to a Zone 10 exposure. I’ve included scans of one of the sheets in Figure 1 below. The non-inverted negative is on the left, while the inverted positive is on the right.
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Figure 1: Tmax 100 film exposed through 4x5" Stouffer step wedge. Non-inverted negative on the left; inverted positive on the right. The dashed box indicates where the base plus fog density measurements are taken (a patch of black electrical tape on the step wedge). The Roman numerals correspond to equivalent zones.
I adjusted the brightness and contrast in the scanning software (Flexcolor 4.0.3) so that the tonal difference in each of the steps would be more clear in this composite image. This was done for purely illustrative purposes and had no effect on the test (the evaluative portion of the test was done with a densitometer and the actual negatives).
All six negatives looked similar to the one on the left-hand side of Figure 1 with only minor variations in density. I’ve labelled the steps in the inverted positive with the corresponding equivalent zone numbers as I find this a useful, if potentially inaccurate, way of thinking about tonality. (I’ll note here that I’m glossing over some of the technical details regarding how a step wedge is used that aren’t particularly important for the interpretation of these specific test results; I'm simply trying to record a series of uniform, repeatable densities on the various sheets of film so that I can make some measurements and comparisons with the densitometer.)
I used a Chamonix 45H-1 camera with a Nikkor-M 300mm f/9 lens, shooting at or near f/22 for all exposures. The metering was done with a Sekonic L-558 in spot mode using an ISO of 100, which is box speed for Tmax 100. The photographs were all made during mid-day under sunny conditions. On the first day, I exposed three sheets (Sheets 1-3) within approximately five minutes of each other under virtually identical lighting conditions (I re-metered before each exposure). On the second day, I exposed an additional three sheets (Sheets 4-6) under slightly brighter (+0.3 EV) ambient lighting compared to the previous day. The slightly brighter conditions on Day 2 were accounted for in the exposure settings for Sheets 4-6. Subsequently, all six sheets should have received essentially identical levels of exposure, say, within +/- one-sixth of a stop (i.e., the metering and exposure settings were all read to the nearest one-third stop, so the standard uncertainty in the measurements should be half that).
All sheets were developed in Adox XT-3 (chemically comparable to Kodak Xtol) using a dilution of 1+1 at 20 degrees C. For processing, I used a Jobo CPE-2 with lift, a 2520 tank, and a 2509n reel with the 4x5 retaining panels installed. The tempering bath of my CPE-2 is equipped with a small circulating pump to help with temperature equilibration and I monitor the temperature with an in-calibration digital lab thermometer. All chemical solutions were prepared using distilled water and ensured to be at the development temperature of 20 degrees C before starting development. Although I only developed one sheet at a time, I used Jobo’s recommended minimum volume of 270 mL for all solutions and processing runs.
For the standard development time, I referred to the most recent Tmax 100 data sheet (see page 4 here). For 4x5 rotary development in Xtol at a dilution of 1+1, Kodak recommends a time of 9:45 (mm:ss). In general, the processing regime went as follows:
(A quick note about Step 7 – Because I’m using Kodak Rapid Fixer, which is based on ammonium thiosulfate, Hypo Clearing Agent (HCA) isn’t really necessary for the purpose of removing residual fixer. It is quite useful, however, for removing the sensitizing dyes that are commonly present in tabular-grain films. I know from experience that these dyes can, if not removed, have a pretty significant effect on densitometer readings, so that’s why I’ve included an HCA step in the developing regime. This step could be eliminated but would need to be compensated for by using much longer wash times.)
- Pre-warm or pre-soak, 5:00 (dry or wet, depending on test type);
- Develop in XT-3 1+1, from 9:45 to 11:42 (depending on test type);
- Kodak Indicator Stop Bath, 0:45;
- Tap water rinse, 0:30 (to prevent acid carryover into fixer);
- Kodak Rapid Fixer, 4:00 (Part A only, no hardener used);
- Tap water rinse, 2 x 0:30;
- Kodak Hypo Clearing Agent, 2:00 (used to eliminate magenta stain);
- Tap water rinse, 2 x 0:30 (to rinse the pour-in channel in the Jobo lift);
- Running tap water wash, 5:00 (using a Jobo Cascade film washer);
- Kodak Photo-Flo 200, 0:45;
- Hang to dry, approx. 60:00.
Once a sheet of film was dry, I used an X-Rite 811 densitometer in Status M mode to measure the visual density of the various steps recorded on the sheet. I checked the calibration of the X-Rite with a calibration target before each set of measurements to ensure it was reading accurately. In total, 22 density measurements were made for each sheet of film – one measurement to determine the base plus fog (B+F) density, followed by an additional 21 measurements to cover each step in the wedge. The density measurements plotted in the charts below are all “net” density measurements, where net density equals the density measurement of each step minus the B+F density.
Sheet 1 is my control sheet and was developed for 9:45 with no pre-soak. To ensure temperature consistency, I used a five-minute, dry, pre-warm step with the tank rotating in the Jobo to develop Sheet 1. Sheet 2 was similarly developed for 9:45, but utilized a five-minute pre-soak in distilled water while rotating in the Jobo. All other development steps were kept the same. The density curves for Sheets 1 and 2 are plotted in Figure 2 below.
View attachment 313413
Figure 2: No pre-soak vs. pre-soak density.
The above result really surprised me. Although I expected some loss of density in the sheet developed with a pre-soak, I didn’t expect it to be this significant. These results do strongly suggest that, at least for this specific film-developer-processor combination, doing a water pre-soak does inhibit development to some degree.
My next step was to develop a third sheet of similarly exposed film using a five-minute pre-soak plus extended development time in an attempt to compensate for the loss in density seen in Figure 2. Sheet 3 was developed for 10:30, which is equivalent to an additional 7.7% of development time over the standard time of 9:45. The density measurements for Sheet 3 are plotted along with those from Sheets 1 and 2 in Figure 3 below.
View attachment 313414
Figure 3: Evaluating the effect of extended development time (+7.7%) following a water pre-soak.
As can be seen in Figure 3, 7.7% wasn’t enough additional development time to compensate for the loss of density due to the pre-soak. I had initially guessed that 5-10% additional development might be enough, so this result was another surprise to me. There’s also a curious observation to be made in the shape of the curve for Sheet 3. Specifically, there's a steeping of the density curve in the highlights near Zones 9 and 10. My instinct is that by extending the development time to compensate for the loss in density due to the pre-soak, we end up with over-development in the highlights. This seems consistent with what photographers generally assume will be the effect of increased development (i.e., greater impact on highlight density and a corresponding increase in overall contrast).
Because these were surprising results, I wondered whether my control sheet (Sheet 1) might not be a fluke (e.g., metering error, etc.). To investigate that possibility, I exposed three more sheets under similar conditions the following day. Sheet 4 was developed as per normal (9:45, no pre-soak) to provide a check on the accuracy of my original control sheet. The density measurements for Sheet 4 are plotted with Sheets 1-3 in Figure 4.
View attachment 313416
Figure 4: Repeatability test on the original control sheet. The density curve for the repeat control test (Sheet 4) closely matches that of the original control test (Sheet 1).
As can be seen above, there’s very little difference in the density curves of the two control sheets. What difference there is can likely be attributed to the +/- one-sixth of a stop uncertainty in the metering and exposure settings. On the whole, I feel Sheet 4 confirmed that my control densities measured in Sheet 1 were accurate and representative of the standard development. Consequently, I’ve chosen to continue using the Sheet 1 density curve for all subsequent comparisons.
Next, I made a second attempt at determining how much additional development is needed to compensate for the loss of density due to the pre-soak. Sheet 5 was developed for 11:42, which is equivalent to an additional 20% of development time over the standard time of 9:45. The density measurements for Sheet 5 are plotted with Sheets 1, 2, and 3 in Figure 5.
View attachment 313418
Figure 5: Evaluating the effect of extended development time (+20%) following a water pre-soak.
This result compared well with the densities in the original control sheet, particularly in Zones 3-8, which suggests that 20% of additional development time may be a good place to start with this film and developer combination. That said, Sheet 5 exhibits the same rapid increase in highlight density that was previously observed in Sheet 3. This is, again, consistent with the idea that extending the development time has a disproportionately large effect on highlight density. This might make extending the development time problematic -- i.e., you can counteract the effect of the pre-soak on the shadows and midtones by simply extending the development time, but doing so may come at the expense of blown out highlights. That said, it’s debatable to what degree we need to be concerned with density in Zones 9 and 10, since we’re usually trying to engineer an exposure in such a way as to avoid recording overly harsh light.
For my final test, I wondered if the duration of the pre-soak might be having an effect on the development. In developing Sheet 6, I reduced the pre-soak time from 5:00 to 1:00 and developed using the standard time of 9:45. The results are plotted with Sheets 1 and 2 in Figure 6.
View attachment 313419
Figure 6: Testing the effect of pre-soak duration on density. The shorter pre-soak (Sheet 6) exhibits less inhibition of development compared to the sheet pre-soaked for 5:00 (Sheet 2).
This was another interesting result. It appears that the duration of the pre-soak does correlate with the degree to which the development is inhibited. Going off my previous hypothesis about how pre-soak water in the emulsion dilutes the incoming developer, it makes sense that a longer pre-soak would result in more water uptake in the emulsion and, hence, greater dilution of the incoming developer. I suspect there are lower and upper bounds to this effect, meaning: The inhibition phenomenon probably begins building at the very moment the pre-soak is initiated, and then reaches a maximum level after a few minutes. Presumably, this would be slightly different for every film type, developer, dilution, and agitation scheme.
To summarize:
Some closing remarks... Your results may vary. I've tried to conduct these tests in as consistent and precise a manner as possible, but given different conditions and a different operator, who knows? Also, this isn't intended to be a true Zone System-style film speed and development time test; I'm simply trying to record some identical latent images on different sheets of film so we can see how the developed densities compare following different development routines. And most importantly, these tests aren't intended to suggest whether doing a pre-soak is "correct". Many people swear by it, many others don't. My intention here was merely to ask (and attempt to answer) a purely scientific question without regard to issues of aesthetics. Hopefully it was useful to you.
- Doing a water pre-soak does appear to inhibit development.
- The duration of the water pre-soak is an important factor -- i.e., the longer the pre-soak, the great the inhibition to the development and the lower the density in the developed negatives (up to a certain point).
- The reduction in density arising as a consequence of the pre-soak can be compensated for in the shadows and midtones by extending the development time (e.g., by +20%), but doing say may simultaneously cause the upper highlights (Zones 9-10) to blow out compared to the highlights in the "standard" development that utilizes no pre-soak.
And just like that, the world stopped prewashing.
I swear, that wasn't my intention!
Pardon me if I commented on this earler. Dunno. But every single type roll and sheet film I've ever used, I presoaked, including Delta 100. It actually helps the developer spread more quickly and evenly. And in the case of sheet film with tray development, I can't imagine shuffling those sheets in developer efficiently without prior conditioning in water. But the whole point is to standardize the length of the presoak and its own agitation cycle, and that's it's neither too short nor too long. I generally use two minutes. It's been a long long time since I've seen an actual technical article about this in relation to different times and different films; but I captured the gist of it in my own practice. And mind you, I'm not talking about just one little experiment, but about decades of experience with many types of black and white film, in multiple formats all the way from 35mm to 8x10.
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