MaxP
Hello!
I recently bought this JOBO cascade for film rinsing to go with my JOBO developing tank.
You can connect it to the tap, but how do you get the water to the right temperature?
I’ve never really managed to get it exactly to 20 °C. Can anyone give me some tips on this?
Or is it perhaps enough just to get the temperature roughly right?
Thanks, Max
SCKStef
Hi Max,
It’s fine if you shoot at around that temperature; most emulsions aren’t too fussy about it.
The exception is older emulsions, like those used in Efke films... where you might end up with something like grain graininess, but I’ve only ever had that happen once, and that was with a water temperature below 10 degrees.
Best regards,
Stähane.
Christoph
Hi Max,
I also use the Jobo cascade, and it works brilliantly for temperature control. First, I turn the tap on until the water flow is roughly right. Only then do I insert the cascade into the Jobo canister whilst the water is running. I place a thermometer in the top opening where the water comes out of the canister. I have a tap with a mixer tap and a boiler. When the temperature rises, I turn the mixer tap slightly towards the cold side, and when the temperature drops, I do the opposite. It works really well.
Chris
joepi
Max,
If you (like me) have a continuous-flow water heater: get rid of the cascade system.
Even in my old flat with district heating, I soon found the thing a bit of a faff. If I have to keep an eye on the temperature and therefore be careful during washing, I might as well use the Ilford method straight away, which uses far less water.
Regards,
JP
MaxP
Hello!
Yes, I also have a instantaneous water heater that can’t maintain the temperature reliably. Even when I pay close attention to the temperature, there are always significant fluctuations.
I’ve just done a test. Once with quite cold water without really checking the temperature. And once ‘by hand’ at exactly 20 °C. I can’t see any difference in the negatives. I’ll take some prints today.
What exactly is the Ilford method for washing?
Regards, Max
Gerd
Unfortunately, when washing, the temperature must remain within ±5°C of the rest of the process (i.e. up to 15 or 25 degrees, if you have developed and fixed at 20 degrees). That is quite a significant difference at first glance, but it should be manageable in most cases. The aim here is presumably to prevent grain wrinkling, which can occur when the emulsion and base expand or contract at different rates due to sudden temperature shocks.
However, I once read a thread somewhere where someone – for educational purposes – tried to induce grain wrinkling. They did not succeed. Most modern films are probably reasonably resistant to this.
The Ilford method goes something like this:
- After fixing, fill the tank once with water and pour it away (to rinse out any surface fixer residue).
- Refill the tank, tilt it 5 times, pour out the water.
- Refill the tank, tilt it 10 times, pour out the water.
- Refill the tank, tilt it 20 times, pour out the water.
- Refill the tank, tilt it 20 times, pour out the water.
- Done.
Gerd
Renate
Hello,
The problem with cold water isn’t so much the grain. I’ve never experienced that. The problem is more that the fixer gets washed out. At cold temperatures, this takes considerably longer than the recommended 5 minutes. This makes it impossible to predict how well the negatives will hold up over time. That’s why I no longer use the Jobo Cascade.
Instead, I use a bucket of water, which I leave to stand for a while until it has reached a temperature of 20 degrees. Then I follow the Ilford method. It takes longer, but it’s safer.
Best regards,
Renate
Wolfgg
The Cascade (that’s how Jobo spells it) makes sense if you’re in a real hurry (like the press labs used to be) and have the water temperature reasonably under control. Otherwise, buckets, sinks and the like are preferable.
The last time I had grain shading was in 1979 with Panatomic-X. That’s when the emulsion tore into lots of little triangles.
Best regards, Wolfgang
bernhardmangelsgmxde
I’ll also vote for the ‘Ilford’ method, as described above; (I’ll just do that later... better safe than sorry)
Cascade: I bought one of those myself at one point; I’ll be putting it up for sale on eBay soon, along with my film scraper (things that haven’t exactly made my darkroom work any easier)...
cfb_de
Hi there,
Back in the day, on two other forums, before this old chestnut was trotted out for the 301st time, I actually worked out how washing works and what you need to bear in mind in terms of timing. A straightforward example that’s easy to follow.
Here are just a few pointers:
- We’re talking about solutions of substances in water (which is why the claim about heavy fixing salts sinking to the bottom is simply nonsense. Pour some saline solution into water and look through the glass vessel to see what it looks like after a while: exactly: homogeneous. And it tastes just as salty at the top of the solution as the ‘bottom sample’).
- Washing is a diffusion-controlled mechanism.
This involves concentration gradients (which makes ‘slow or fast washing’ irrelevant; what remains important is ‘washing’) and temperature gradients.
Based on calculations and supporting chemical analysis, I conclude that temperature plays a rather minor role (i.e. in film rinsing, we’re talking about a range of just a few seconds at a temperature difference of 10°C between 10°C and 20°C).
Of course, the temperature becomes interesting for high-altitude laboratory technicians for other reasons when the gradient is between 0°C and 10°C. They then have to grapple with transient diffusion, which, to make matters worse, comes on top of the question of whether the propane burner can even ignite at all at the prevailing air pressure.
Once completely freed from faith, from the love of long-established processes, from hearsay in the literature: even the ‘Ilford washing’ with 10°C cold water is already too much of a good thing. And any washing machines are superfluous if you wash each print individually. Moreover, for a 30x40 baryta sheet under unfavourable conditions (high-key print on silver-rich paper), you don’t need 500ml of water. Anything beyond that is merely a matter of appeasing one’s conscience and has more to do with parapsychology than with photographic chemistry.
However, such things are not found in a prayer book, but can only be discovered through proper analysis. That is, with test strips and measurements, and the occasional proper spectrometry. Hardly any devotee of washing has done this. Eder started it, and from then on trivial writings reigned supreme, much like the ‘iron in spinach’ debate. One author copied from the next.
Best regards,
Franz (chemist, has tested it to certification standards)
Andreas_23
Hi Max,
I can’t explain it as well or as thoroughly as Franz, but I too think using a rinsing aid is unnecessary. Once the fixing process is complete, the film is light-insensitive. So why make it so complicated and rinse through the hole in the developing tank? I just open the tank, pour out the fixer and place the open tank under running water for a few minutes. I’ve never had any problems with this method (though I did have issues with the Cascade, which kept slipping off the tap).
Best regards,
Andreas
Renate
Hello,
Rinsing the film is crucial for its long-term stability and should not be taken lightly. Only if the fixer is completely rinsed out can the film be stored for many years without damage. The Jobo Cascade is the ideal tool for this. I am not aware of anything better. The only issue is the water temperature. It should be around 20 degrees, because at lower temperatures, rinsing out the fixer can take considerably longer than the recommended 5 minutes. The chemical processes involved are temperature-dependent. As I cannot regulate my tap water to around 20 degrees, I have switched to the Ilford method. It also produces good results, but takes considerably longer.
Best regards
Renate
Wolfgg
It’s just that, dear Renate, it takes a bit of time to wash it all out :rolleyes:. As you surely know as a physicist, the blighters have set up a nasty inverse exponential function...
Best wishes, Wolfgang
cfb_de
Hi Wolfgang,
Anyone who fancies it can work out the non-steady-state diffusion for themselves :-) I did a preliminary calculation for a steady-state system at some point over the last few months. Even this significant simplification yields surprisingly good results, as I’ve verified through chemical analysis (you know I’m neither an engineer nor a physicist).
Ah, I’ve found it again:
http://phototec.de/phorum/read.php?3,17892...8937#msg-178937
It may come as a surprise to many who rely on the literature that the temperature effect is actually not all that significant. And it may be just as surprising to many that the washing times can also be kept quite short (an engineering approach would be to double the minimum time obtained from the developer). In fact, with HP5/7°C/Jobo 1236/1 l min⁻¹ after 150 seconds, I could not detect any difference compared to longer washing.
Condition: The tank is first cleared of any residue of the fixer before the official start of rinsing. After pouring out the fixer, simply rinse twice quickly with water. Then (with my process and under my conditions here) about three minutes is sufficient for archive-safe film rinsing.
And I certainly don’t bother fiddling with the Cascade on the tap. I just unscrew the can and let the water run directly from the tap into the centre tube. For paper, I’ve built myself a semi-automatic wetting unit using a dual-wash water pump repurposed from a car: it turns over, drains after 30 seconds and refills itself. A 12V power supply, a synchronous motor with a gearbox, three relays.
In my view, the Cascade has several effects:
- It’s a laboratory device. So it *must* be good, and you believe in it.
- It hisses and bubbles. So something’s happening.
- It costs money. So it *is* good.
- Everyone uses it. So *you have to use it*.
However, this device lacks the most important effect: it has absolutely no influence whatsoever on the processes taking place during washing! No decent diffusion can be disrupted by bubbling water at the top of the Cascade down into the can, where the flow is once again almost laminar.
Interestingly, in the specialist literature, I found the most sensible comments on washing in the work of the late Hofrat Eder. Everything since then has been nonsense of the ‘long and with plenty of water’ variety, without any substantiation of the claims.
Best regards,
Franz
Wolfgg
Hi Franz,
Thanks very much for the link to your theoretical thoughts. Differential equations, Laplace transforms and the like used to drive me up the wall for ages. They were often used to weed people out.
With the cascade, I always found it so funny that you have to plug a hole and then turn the tap on until the water level is between two marks.
Regards, Wolfgang
ibucgn
If I’ve understood the pros and cons of the Jobo Cascade correctly, then surely the Cascade doesn’t offer much more than the Ilford method and similar techniques. But: apparently, the Cascade doesn’t do any harm either, does it? In any case, I’ve always rinsed with the Cascade so far, and I haven’t noticed anything negative about the method yet. What’s more, as I have a thermostatic mixer tap on the bath (where the aerator has been swapped for a hose nozzle using an adapter), a reasonably stable water temperature is even guaranteed. Well, the water temperature does seem to be negligible, as explained here and in the thread linked by Franz in the parallel forum...
Wolfgg
I’ve also done a bit of calculation regarding the rinsing solution. So, I’ve taken what Franz worked out ‘over there’ on paper and applied it to a 500ml can, looking *exclusively* at the residue of thiosulphate. The question is: what is the achievable residue of thiosulphate with a simple water change in the can?
The “worst-case film”, namely a highly sensitive film (30 DIN and above), has a layer thickness of around 20 µm. With KB36, this results in a dry gelatine volume of approximately 1 cm³ (20 µm × 1.6 m × 35 mm). However, when emptying a tank, more remains behind: the residue on the inner wall, the spiral and, above all, the droplets on both sides of the film are likely to amount to a good 5 cm³ in total. With a 500 cm³ tank, this means that each water change results in a dilution of the salt solution of approximately 1:100. This means that if, with every water change, you allow the salt sufficient time for the concentration to equalise (according to Franz’s calculations and tests, 3 minutes is already on the safe side), the fixing salt concentration drops to one millionth of the concentration during fixing by the third wash (1:(100*100*100)).
And what do we need; what residual salt concentration is permitted? For 100 years of archival safety, the concentration must be below 50 mg per square metre of film (more details at
http://silvergrain.org/wiki/Washing), i.e. 2.8 mg of residual salt per KB36/120 film. At 150 g of salt per litre, 1 cc contains 150 mg of salt. The first water undergoes a dilution to 1/100, i.e. 1.5 mg/cc. If the salt concentration in the film layer were to fully equalise with the water concentration (which theoretically takes an infinite amount of time, but in practice is sufficiently achieved after 3 minutes), there would be only approx. 2 mg of salt left in the film layer (volume 1 cc, perhaps 1.3 cc due to gelatin swelling), i.e. archival safety is already achieved with the first rinse! With the second water, the film contains only 0.02 mg of salt after 3 minutes, and so on.
For thiosulphate, this would mean: after fixing, simply
1) pour water into the tank once, then empty it immediately (=rinse)
2) add water again, wait 3 minutes (=film wetting)
Archive-safe washing is now complete!
Reasoning:
In step 1), the residual fixer outside the emulsion layer is diluted to 1/100; over 90% of the fixer in the tank is now contained within the emulsion layer.
In step 2), the fixer in the emulsion is distributed throughout the total volume of water, i.e. a dilution of 1:300–500, resulting in <0.5 mg salt/ccm (target: <2.8 mg/ccm).
The only question now is: what about the other salts present in the emulsion? Are there any that compromise archival stability and are not sufficiently removed from the emulsion within the 3 minutes?
Regards, Wolfgang
cfb_de
Hello Wolfgang,
Thanks for the simple calculation :-)
Yes, you can’t look at it in terms of the thiosulphate ion alone. Various silver thiosulphate complexes are formed, each with different solubility and stability.
There are also halides in the emulsion, which also affect the film’s archival stability.
However, it is indeed the case that these water-soaking sprees are as much a myth as the high iron content in spinach.
In any case, my press films back then were only rinsed for 1 minute and then rinsed with alcohol. Otherwise, the prints would never have made it to the editorial office in time. The prints are mostly fine (they only have to last a few hours, after all), and the negatives are still perfect even after 20 years.
Best regards,
Franz
Wolfgg
Hello Franz,
So the most sensible way to rinse the film is as follows:
1) Pour water into the tank once, then drain it immediately (= rinse)
2) Pour water in again, wait 3 minutes
3) Pour water in again, wait 3 minutes
Done.
After step 2), the thiosulphate has already been sufficiently removed; step 3) serves as a safety rinse for ‘special products’ that may have formed as a reaction between the developer, stop bath and fixer. And you can save yourself the hassle of tilting the can; everything is done with the can open and without a lid. Afterwards, the films will even survive the next generation, if there is one.
I also have some test negatives from 1970 that were rinsed “unacceptably sloppily”, and they look no different from the thoroughly rinsed ones.
Regards, Wolfgang
Renate
Theory and practice,
Over the years, I have seen many valuable films and photographic plates that were irreversibly damaged due to insufficient rinsing. Yet, in these cases, the rinsing had been much more thorough than the calculations in the theoretical considerations above would suggest.
A theory is only valid once it has been confirmed experimentally. With that in mind, I hope you enjoy carrying out your own measurements.
Best regards,
Renate
