Twist agitation - has anyone ever done tests?

[Craig]

This led me to believe that technique may be a much larger factor than originally anticipated.

It probably is. I usually have the end of the film such that when I turn the reel, the fluid goes in that end of the film and would be pushed through the spiral. It actually exactly mimics the shape of the impeller of a water pump. I think that pushes the developer from the outside of the tank to the core.

I have not done densitrometry to test my theory, but simply by inspection I don't notice any end to end variation (on 120 film anyway), and I don't notice frames at the end of the roll printing differently from the beginning.

 

[AgX]

In this context one may wonder why Jobo over 50 years ago omitted that stick. I mean, their savings were just that stick but then they could not say their tanks would please everyones manner of processing.

I assume that at their main markets in the 60's that twisting was regarded as inferior manner of agitation.

 

[Craig]

In this context one may wonder why Jobo over 50 years ago omitted that stick.

Does Jobo make tanks designed for hand processing? The only ones I have ever seen are intended to fit their machines.

 

[AgX]

All 1500 and 2500 tanks they offer at their site and their catalog are manual tanks that have to be upgraded to be used on a processor. In the past these models were offered in two versions.

They make daylight tanks since about 100 years.

 

[gorbas]

So, what is "Dobro method"? Did anybody figured it out?
Recently I start using twiddle stick to rotate reels in first minute of developing only.
Pour developer in, turn tank 5 times upside down to the right, 5 times to the left (basically first 30 sec) and then rest of the minute agitate with the stick. Then for the rest of developing 3 upside down agitation per minute.
While washing film (by ilford method) open the lid of the tank and you can observe what happens to trapped air bubbles in the grooves of the reel when you use the stick. It's very interesting!

 

[Craig]

All 1500 and 2500 tanks they offer at their site and their catalog are manual tanks that have to be upgraded to be used on a processor. In the past these models were offered in two versions.

Never knew that the tanks had to be upgraded to be used on a processor. Mind you, I haven't seen Jobo equipment in any photo store here for decades - probably the last time was in the 90's and there wasn't much then. It's rare stuff.

 

[Sirius Glass]

In this context one may wonder why Jobo over 50 years ago omitted that stick. I mean, their savings were just that stick but then they could not say their tanks would please everyones manner of processing.

I assume that at their main markets in the 60's that twisting was regarded as inferior manner of agitation.

Jobo tanks do not need a stick. They were designed to be used with the Jobo processors. AgX you really need to get on board.

 

[AgX]

Jobo tanks do not need a stick. They were designed to be used with the Jobo processors. AgX you really need to get on board.

I am on board. Just read what I have posted in this in this thread. Jobo make tanks for about 100 years. Have you got a Jobo processor that old?

And as I just explained Jobo today even sell tanks that as such cannot even be used in their processors but must be upgraded.

 

[eli griggs]

I've no done tests, however, I have always introduced a twist in my developing tank/stop/fixer tanks, steel or Patterson, on the down fall and the rise.

This is, in my opinion, the best option to any agitation, no matter how short or long the development, exception being still bath development.

Cheers.

 

[BCM]

With that few rotations, the developer in the middle of the spiral would move very little.
You might get compensation if you have very generously exposed shots or you’re pulling. But otherwise I’d start carefully inspecting my negatives.

The spool/film keep this from happening.

 

[Helge]

The spool/film keep this from happening.

It’s exactly what makes it happen.
It’s not an eye of the storm phenomenon if that’s what you think I mean?

 

[AgX]

But Craig described just this for a Paterson tank at post #37.

 

[250swb]

I think if a photographer uses just a couple of films any form of agitation or rotary processing can work because you learn the quirks of the film and developer, put bluntly you learn from your mistakes. But if a photographer uses a wider range of films and likes to change developers I think it's worth sticking with the twiddle stick because it eliminates common faults or accidents of inversion such as surge, foaming, air bubbles, etc. None of these things come into the equation with the twiddle stick because not matter what developer or strength of developer you will not get surge around the sprocket holes, it can't foam, or make air bubbles etc. A different approach from 'I've never had a problem (yet)' to 'let's not start out by encouraging potential problems'.

So I use the twiddle stick almost exclusively with Paterson tanks with the exception of a couple of film and developer combinations where I just swish the developer gently in a circular motion. But the twiddle stick shouldn't be used like a ham fisted gorilla, gentle turns are all that is required, you aren't trying to create vortices, just enough to keep putting fresh developer on the film. I think the twiddle stick is also more reassuring for techniques such as semi-stand developing where you don't have to worry for three or four minutes if you banged the tank hard enough to disperse air bubbles after the previous inversion. The whole point of using the twiddle stick is to mimic the only sure fire way to process successfully every time, which is a deep tank, where you aren't plunging the film in and out of the developer by way of agitation, just moving the spiral around in the liquid, usually D-76 the last time I used a deep tank.

 

[BMbikerider]

When you think of it, those of us who use a JOBO rotary processor to develop films are doing the same actions as a 'twiddle stick' but with the tank on it's side. and using less chemicals to do the same task. The agitation is constant unlike bench agitation with the stick.
Yes I have occasionally noticed unevenness when developing colour C41 this way, but I am not sure that it is all down to the method of agitation because it is always down a few of the short edges on random frames on the length of film and never on black and white or 120 C41. I can go for weeks without a problem and then I get a couple of films where the problem crops up.
Because the shutters of my cameras all have vertical travel and not horizontal that would discount any problem with the shutter causing uneven exposure and not my developing. I think that will have to remain as one of life's mysteries.

 

[BMbikerider]

Does Jobo make tanks designed for hand processing? The only ones I have ever seen are intended to fit their machines.

All their tanks can be use for inversion agitation apart from the model 4312 (120) tank which has a hole in the top cap which eliminates the 'gassing' when the bleach is poured into a tank that has the remnants of developer. That is designed exclusively for rotary processing.

 

[AgX]

When you think of it, those of us who use a JOBO rotary processor to develop films are doing the same actions as a 'twiddle stick' but with the tank on it's side.

No, they don't.

The difference is that at stick twisting the reel is fully immersed into the bath, but at rotational agitation you got a fluid level parallel the rotation axis, which affects fluid dynamics.

 

[MattKing]

No, they don't.

The difference is that at stick twisting the reel is fully immersed into the bath, but at rotational agitation you got a fluid level parallel the rotation axis, which affects fluid dynamics.

In addition, rotary agitation in a JOBO induces much more mixing of solution and air than just using the twist agitation stick.

The whole point of using the twiddle stick is to mimic the only sure fire way to process successfully every time, which is a deep tank, where you aren't plunging the film in and out of the developer by way of agitation, just moving the spiral around in the liquid, usually D-76 the last time I used a deep tank.

This is an interesting viewpoint, because the not recommended by the manufacturer (Paterson) method of using just twist agitation is to my mind, more unlike deep tank agitation than inversion.
The twist stick agitation is the least randomnized form of agitation I know of.

 

[BMbikerider]

No, they don't.

The difference is that at stick twisting the reel is fully immersed into the bath, but at rotational agitation you got a fluid level parallel the rotation axis, which affects fluid dynamics.

The action is the same and when used on the slow speed of rotation and counter rotation that should not make a great deal of difference except as the agitation is constant the development time has to be cut. Jobo recommend 15% reduction. that is fine for colour, but for B&W, 20% is usually better. The overall density doesn't change that much but the contrast is brought to within usable parameters.

 

[AgX]

This whole discussion reminds at that of the pre-wash... in the sense that I started with photography long after that stick vanished over here, practically came across no hints to it, until I joined Apug. And this very thread even surprised me with so many fellows sticking to that stick.

 

[BrianShaw]

This whole discussion reminds at that of the pre-wash... in the sense that I started with photography long after that stick vanished over here, practically came across no hints to it, until I joined Apug. And this very thread even surprised me with so many fellows sticking to that stick.

perhaps you should feel gratified that you are now aware of another photography technique!

 

[AgX]

Yes, Apug is enlightened.

 

[eli griggs]

Yes, Apug is enlightened.

Yes, but can it tell us if we need to twiddle rotate to the left in the upper hemisphere or to the right down below the equator?

At what descent or accession at the actually line of the maximum belt parallel determines or just implies a "Best Practices" point of decision?

 

[250swb]

The twist stick agitation is the least randomnized form of agitation I know of.

You can turn it clockwise or counter clockwise, you can turn it back and forth, you can turn it two or three times or five or six, you can turn it quickly or turn it slowly, so that is seven options that can be combined, which I think makes 5040 permutations of twiddling. If rather than a vague two or three or five or six twiddles you added them as individual numbers 2,3,4,5,6,7,8, etc. it would go into the millions of permutations that can be introduced in the twiddle method. All a photographer has to do is not make it the exact same combination two times in a row but still be consistent, use common sense, and incorporate the technical requirements of the film and developer. How many permutations to randomise agitation are possible with the inversion method?

 

[BrianShaw]

Yes, but can it tell use if we need to twiddle rotate to the left in the upper hemisphere or to the right down below the equator?

At what descent or accession at the actually line of the maximum belt parallel determines or just implies a "Best Practices" point of decision?

Twist direction is not really a matter of geography. Direction of twist depends on the spool, whether it is a clockwise or counterclockwise spool. That’s why it’s important to twist in both directions to split the difference and twist I both directions for consistent processing. Special processing may be required for anticlockwise spools.

 

[AgX]

Can it tell use if we need to twiddle rotate to the left in the upper hemisphere or to the right down below the equator?

Which reminds me to say that I was wrong with saying that at some old Jobo tanks one only could twist clockwise. It was anti-clockwise instead. And at these you cannot invert the spiral...