[lithedreamer]

Some general film developing information. Ilford's published development times in their DD-X Data Sheet

And per the DD-X data sheet under the Manual Processing Spiral Tanks, they say to invert the tank 4 times within 10 seconds of each minute of development. It's a good idea to read the data sheet for every chemical and film you use.

That's good info, thanks. The chemicals came with instructions, but nothing this detailed. I don't do inversion agitation, do you know how that translates to 'stir agitation'?

[tuco]

That's good info, thanks. The chemicals came with instructions, but nothing this detailed. I don't do inversion agitation, do you know how that translates to 'stir agitation'?

Sorry, no I don't.

But also take note of why we have to agitate film in the first place. It is because only a very, very thin layer of the developer is actively developing the film. It's an area called the boundary layer in fluid mechanics. When the developer gets exhausted in this boundary layer, we need to shake the tank to get a "fresh layer" of developer next to the film.

Now if that agitation is slow and gentle, you can also get what is called laminar flow across the boundary layer in fluid mechanics. That is, the same exhausted developer moves across the surface of the film never getting replenished enough and we can get uneven or streaky development. So we need to make sure the agitation is turbulent enough to put a fresh layer of developer next to the film. So make sure your "stir method" is random enough.

[ChrisPlatt]

Loaded reels must be completely immersed but don't overfill your tank i.e. always allow an air space above them.
If developing tank is completely filled with developer agitation - especially by inversion - will be much less effective.

Chris

[Alex645]

That's good info, thanks. The chemicals came with instructions, but nothing this detailed. I don't do inversion agitation, do you know how that translates to 'stir agitation'?

For years I used the Paterson agitation stick to slowly rotate the reel in the tank about 10 seconds per minute, but I may have found if you donʻt rotate/spin the reel at just the right speed, I was getting what Tuco mentions as laminar flow.

Ever since Iʻve been using inversion agitation which is more similar to what is done with metal developing tanks. After adding the solution, Iʻll knock the bottom of the tank a couple times to release any air bells, then with the Paterson tank stir for 10 seconds then cover everything with the lid. Every 60 seconds I invert the tank twice for the remaining development or fix time. In lieu of stirring with the agitator, you can do the inversion with a twisting figure 8 type motion. Keeps your wrists limber and makes the time pass better with the right music.

[lithedreamer]

For years I used the Paterson agitation stick to slowly rotate the reel in the tank about 10 seconds per minute, but I may have found if you donʻt rotate/spin the reel at just the right speed, I was getting what Tuco mentions as laminar flow.

Ever since Iʻve been using inversion agitation which is more similar to what is done with metal developing tanks. After adding the solution, Iʻll knock the bottom of the tank a couple times to release any air bells, then with the Paterson tank stir for 10 seconds then cover everything with the lid. Every 60 seconds I invert the tank twice for the remaining development or fix time. In lieu of stirring with the agitator, you can do the inversion with a twisting figure 8 type motion. Keeps your wrists limber and makes the time pass better with the right music.

Eh, I really don't care for the inversion method. I always find the Paterson lid such a fuss to get sealed (and otherwise it leaks), at least on my tank. Having to do that over and over again is my main objection.

[Alex645]

Eh, I really don't care for the inversion method. I always find the Paterson lid such a fuss to get sealed (and otherwise it leaks), at least on my tank. Having to do that over and over again is my main objection.

On mine, securing the lid is no more difficult than putting the top on a Tupperware container. And I only put it on once for the developer and once for the fix. As stop bath is less than a minute, I donʻt bother with inversion and thus no lid needed.

When I demo for my high school students, they remember because I tell them to not forget what their parents often tell them: "Put a lid on it." Thereʻs always one student that then rolls her eyes and says, "OMG, a Daddy joke".

[Digitalis]

I recently got a laboratory grade hotplate/magnetic stirrer unit [ I got it cheap as the heating element had burnt out] and a few magnetic/ceramic stirring bars. I find at low RPM stirring settings ( you don't want to create cavitation bubbles) it is well suited for large and medium format film developing - especially when i'm developing by inspection as the movement of the developing solution is in constant, controlled motion. I haven't tried it with my 35mm tanks as I don't think there is enough clearance for the stirrer bar and the bottom film reel, and how much film is on reels I doubt there would be sufficient flow around the film for this to be reliable.

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Last edited by Digitalis; 01-18-2017 at 10:53 PM.