Uneven development

1. What developer are you using?

2. I suspect the reason the twizzle stick exists at all is because agitating in the first few seconds after pouring in is critical for even processing, especially when adding developer to dry film. It's much quicker to get the stick in and twizzle than to get the lid on, burp it and invert. But after those first few seconds, inversion makes better sense.

snusmumriken said:

1. What developer are you using?

2. I suspect the reason the twizzle stick exists at all is because agitating in the first few seconds after pouring in is critical for even processing, especially when adding developer to dry film. It's much quicker to get the stick in and twizzle than to get the lid on, burp it and invert. But after those first few seconds, inversion makes better sense.

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That, plus it very effectively gets rid of air bubbles!

The whole point of agitation is to introduce fresh(er) developer to the emulsion to replace partially exhausted developer during the development process. This is achieved by creating turbulence within the development tank.

During the initial filling of the tank there will be enough turbulence and this will suffice until you fit and burp the lid before commencing your initial inversion agitation of recommended 30 seconds. Inversion speed 2 - 3 seconds per inversion.

Subsequent inversion agitation of 10 seconds per 30 secs / 1 minute as per Kodak / Ilford (per your religious persuasions) should only require 3 - 4 gentle inversions. You are not shaking an aerosol paint can! If you are really paranoid you can rotate the tank 90 degrees when placing it back on you benchtop.

Rapping the Patterson tank on the benchtop can result in chipping the base of the tank. My 48 yo Paterson tank has the chips to prove it. Long ago I settled on rapping the bottom of the tank with three fingers is sufficient to shake any air bubbles loose. Three or four hard raps will do the trick.

Using the twizzle stick exclusively for agitation will reduce the process of bringing fresh developer from above the spool down into the spirals. The total amount of developer must be able to pass through the spirals to achieve an even mixing of the spent and fresh parts of the solution.

Patersons recommendations for solution volumes per film are minimum requirements and a bit more solution will not hurt. When developing 35mm film in HC-110 at dil. H (1+63) I use a total of 320 ml of solution, 5 ml syrup and 315 ml water. This gives a bit of headroom above the spool over the 290 ml that Paterson recommend, (and who can do the maths and accurately measure the amount of syrup required for 290 ml total volume of developer. Just use a bit more solution whatever developer you use.

I started developing in Paterson tanks in 1973 and I have never seen air bells or streaking. No internet in those days. Self taught from a couple of books - a Paterson Darkroom Guide and a book by English photographer Kevin McDonnell. It's never been rocket science. Kodak and Ilford have published screeds of documents on processing film in small tanks. Begin by following their advice and don't deviate until you have the basics under control and you have a good reason to do so. And be CONSISTENT!!!

grain elevator said:

That, plus it very effectively gets rid of air bubbles!

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Yes that is what John Finch says in his interesting demonstration of how to use a twizzle stick Here it is:


Worth a look IMO

pentaxuser

My favourite way to agitate with a Patterson tank, are vigorous figure eights. I always get even development.

pentaxuser said:

Yes that is what John Finch says in his interesting demonstration of how to use a twizzle stick Here it is:


Worth a look IMO

pentaxuser

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John Finch is one of the best YouTubers for film processing. I've subscribed to his channel and I even bought his book. Lots of great info in a single source.

Although the video linked to demonstrates use of the twiddle stick in all of his other videos he uses inversion agitation and his inversion cadence is slow and even.

Andrew O'Neill said:

My favourite way to agitate with a Patterson tank, are vigorous figure eights. I always get even development.

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When you state vigorous inversion I think of shaking a cocktail or an aerosol paint can. Can you give us an idea of your inversion cadence for the nominal 10 seconds of agitation. Are we talking about 5, 10, 20 inversions?

I have not found a bulletproof method for avoiding an occasional uneven development. You can:

• Agitate strictly in accordance to Kodak or Ilford datasheet.
• Use machines like JOBO with regular or alternating rotation.
• Use machines like Heiland TAS with inversion+rotation.
• Pre-soak film or not.

... and still occasionally observe uneven development with some film+developer combinations every once in a while. It's almost a phantom problem and reminds me the endless "can't get a roll onto a JOBO/Paterson reel in a bag" threads, where everyone agrees that it's humidity but somehow some folks have much higher success rate than others that aren't explained by humidity difference.

But thinking logically, I am convinced that most rolls are unevenly developed. The crude mechanics of pouring liquids in/out of small tanks, varying liquid movement in the different parts of the roll on a reel (inner/outer), and intermittently agitating for short period of time, all of that makes it hard to believe that an entire surface on a roll ever achieves 100% uniform development, but it's not always noticeable. Factors such as uniform subject matter, under-development, under-exposure, development time, and gamma boost post-scanning makes it more noticeable in some cases vs others.

Just last night I got unevenly developed 120 roll of Fomapan 100 using TAS film processor. First time in two years of owning the processor and shooting Foma almost continuously. Why did it happen? I don't know.

tokam said:

John Finch is one of the best YouTubers for film processing. I've subscribed to his channel and I even bought his book. Lots of great info in a single source.

Although the video linked to demonstrates use of the twiddle stick in all of his other videos he uses inversion agitation and his inversion cadence is slow and even.


When you state vigorous inversion I think of shaking a cocktail or an aerosol paint can. Can you give us an idea of your inversion cadence for the nominal 10 seconds of agitation. Are we talking about 5, 10, 20 inversions?

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I never invert the tank. I find that to be too aggressive. I hold the tank with one hand over the top of the tank, and do a figure 8 pattern, continuously for the first 30 seconds. Then 5 figure eights every minute.

Andrew O'Neill said:

I never invert the tank. I find that to be too aggressive. I hold the tank with one hand over the top of the tank, and do a figure 8 pattern, continuously for the first 30 seconds. Then 5 figure eights every minute.

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In what sense 'too aggressive'? Apart from an initial twiddle, I always invert. Am I overlooking some terrible consequence?

snusmumriken said:

In what sense 'too aggressive'? Apart from an initial twiddle, I always invert. Am I overlooking some terrible consequence?

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With 35mm film, you run the risk of surge marks on the films which results from the developer roaring through the performations. I've even gotten surge marks with 120 film. Some films are more susceptible to this than others.

Andrew O'Neill said:

With 35mm film, you run the risk of surge marks on the films which results from the developer roaring through the performations. I've even gotten surge marks with 120 film. Some films are more susceptible to this than others.

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For the record, I do semi-stand development with 35mm and do not get streamers. I use Ilford films in a 2-bath developer, and (after an initial twiddle) agitate with continuous inversions in bath 1 and a semi-stand regime in bath 2. No problems whatever. Maybe problems depend on the developer as much as the film?

I've always used the stick for agitation in a Paterson tank and I've have never had streaks. Always nice even development for both 35mm and 120.

My technique is after filling and rapping the tank to dislodge bubbles, then turn the stick quite quickly for about 5 seconds to get both the film and developer moving. Then abruptly stop the stick and the reel and let the developer flow past the film. I don't invert because of the time it takes for the developer to flow through the stick aperture is quite long, I'd rather keep the film immersed in developer.

Andrew O'Neill said:

I never invert the tank. I find that to be too aggressive. I hold the tank with one hand over the top of the tank, and do a figure 8 pattern, continuously for the first 30 seconds. Then 5 figure eights every minute.

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Andrew, I'm really curious to see your figure 8 pattern of agitation. Isn't short video of it long due to enrich your YouTube channel?
Looking forward to see it!
On the same note, about John Finch videos, does anybody know where to buy this darkroom timer I saw in his video?

gorbas said:

On the same note, about John Finch videos, does anybody know where to buy this darkroom timer I saw in his video?

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If you drop him an email at pictorialplanet@gmail.com he'll probably reply. I recently asked him a question via email and he responded quickly.

Edit: It looks to be the one described here:

These clockwork darkroom-timers come up on a reasonably regular basis on the U.K. e-bay. They were made in their tens, may be hundreds of thousands or millions in the 1950-60s but of those that survive they are getting old now. Most are well used so be aware of that and finding anyone now who knows how to repair them if they go wrong can be difficult and this expensive

If you find one even of the outside looks good, I'd ask about it age and use. Occasionally one will come up that has hardly been used. If this is the case they will not be cheap but are likely to be worth it for reliability

I see no reason why they should not appear on other countries' e-bay sites as well

pentaxuser

gorbas said:

On the same note, about John Finch videos, does anybody know where to buy this darkroom timer I saw in his video?
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I've got one surplus to requirements tht you can have if you will pay shipping. DM me if interested and I'll send you photos. May take a few days, as I'm just heading off on hols.

McDiesel said:

and still occasionally observe uneven development with some film+developer combinations every once in a while. It's almost a phantom problem and reminds me the endless "can't get a roll onto a JOBO/Paterson reel in a bag" threads, where everyone agrees that it's humidity but somehow some folks have much higher success rate than others that aren't explained by humidity difference.

But thinking logically, I am convinced that most rolls are unevenly developed. The crude mechanics of pouring liquids in/out of small tanks, varying liquid movement in the different parts of the roll on a reel (inner/outer), and intermittently agitating for short period of time, all of that makes it hard to believe that an entire surface on a roll ever achieves 100% uniform development, but it's not always noticeable. Factors such as uniform subject matter, under-development, under-exposure, development time, and gamma boost post-scanning makes it more noticeable in some cases vs others.

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For the large part, most people aren't flashing their film to specific grey densities, developing (etc) & reading the results at specified intervals across the film with calibrated densitometers - which is essentially the standardised way to measure evenness of development. That said, there seem to be a number of elements that contribute to getting sufficiently even development on roll film (i.e. 135/120) - efficiency/ speed of total immersion in the developer (rapid but not forceful - and a big reason why stainless steel tanks aren't a great idea if you can't work in the dark - they are intended to have the loaded reel(s) dropped straight into the developer, then the lid jammed on and agitation started post-haste), the shortest possible interval from immersion to initiation of first agitation cycle (where a machine like the TAS fails), decisiveness of that agitation (weird wrist tangling methods, overly gentle tilts, worrying about tilting in different directions all are not a good idea - a decisive 2.5-3s upright to inverted to upright cycle seems about right) - and possibly the cross-section of the material used for the reel (Paterson's thin, square edge of the spiral section possibly being better than the thicker round edge of stainless reels).

If all else fails, troughs and continuous agitation are the answer.

And as for loading reels, it seems a combination of psychological phenomena and aspects of fine motor control. Some struggle massively with 120 and not at all with 135, others are completely the other way round. And none of the online complainers seem to ever dare to report the number of times they screwed up getting a roll into a stainless reel - in fact it often seems suspiciously close to a confirmation bias derived from errant quality perceptions based on socially mandated ideas of material quality hierarchies (rather than the chemical or rheological realities).

Richard J. Henry in 2nd edition of Controls in B&W photography wrote about univenes od film development. Unfortunately he mostly used 6x6/120 as base of most of his experiments. To fix non uniformity he even made his own motorised processing rig but never show the drawing or photograph of it.

gorbas said:

Richard J. Henry in 2nd edition of Controls in B&W photography wrote about univenes od film development. Unfortunately he mostly used 6x6/120 as base of most of his experiments. To fix non uniformity he even made his own motorised processing rig but never show the drawing or photograph of it.
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And what is unfortunate about the 6x6/120 film base? Mamiya, Rollei and Hasselblad would disagree with that observation.

Sirius Glass said:

And what is unfortunate about the 6x6/120 film base?

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Nothing, but it allows people to try and hand-wringingly wriggle their way past Henry's conclusions rather than getting their processes under baseline control.

Lachlan Young said:

Nothing, but it allows people to try and hand-wringingly wriggle their way past Henry's conclusions rather than getting their processes under baseline control.

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"There are non so blind as those who refuse to see."

gorbas said:

Richard J. Henry in 2nd edition of Controls in B&W photography wrote about univenes od film development. Unfortunately he mostly used 6x6/120 as base of most of his experiments. To fix non uniformity he even made his own motorised processing rig but never show the drawing or photograph of it.
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According to the table, the "ISO/ASA METHOD" is much better than all others.
What is that method?

Mark Overton

albada said:

According to the table, the "ISO/ASA METHOD" is much better than all others.
What is that method?

Mark Overton

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I bet Stephen knows
@Stephen Benskin being the person I mean.