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Inside Paterson tank

AndreyV

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May 3, 2012
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Hi guys,
Sorry for my English.
I use reel agitation and it was very interesting for me what is going on inside Paterson tank. Is agitation effective or not? How bottom layers of developer mix with middle and top layers? Because main task of agitation (except stand approaches of development) is to move exhausted developer away from film and to bring fresh developer to film surface. I have made small experiment:
1) glass tank (exactly as Paterson tank);
2) Paterson reels with 120 film (unexposed Across);
3) water;
4) small tea leaves (will help us to detect layer mixing).
We will rotate reels with different ways and different velocity. We will try to choose convenient way for agitation.
Look at my small Dead Link RemovedDead Link Removed).
I was very surprised to conclude that uniform rotation is a worst way to achieve mixing of layers. And powerful rotation (clockwise/counter clockwise) gives us the best results.
I think this information will be helpful for somebody.
 
Your video confirms what tests on evenly exposed films showed, that with continuous uniform rotation a laminar flow pattern evolves.

You might do an advanced test and use coloured layers, by "stacking" differently dyed layers of fluid. You would have to do so by inserting the fluids with the reel already inside the beaker.
 
AgX said:
Your video confirms what tests on evenly exposed films showed, that with continuous uniform rotation a laminar flow pattern evolves.
Click to expand...
Yes, you absolutely right. During uniform rotation we get the next: speed of reels=speed of liquid => no mixing => looks like stand development
So uniform rotation is a worst way of agitation.

You might do an advanced test and use coloured layers, by "stacking" differently dyed layers of fluid. You would have to do so by inserting the fluids with the reel already inside the beaker.
Click to expand...
It's interesting.
 
AndreyV said:
blich and fix goes out through Paterson's cover.
Click to expand...

So does everything else! I don't think I own a tank which doesn't force me to wash my hands after every inversion.


Steve.
 
Steve Smith said:
So does everything else! I don't think I own a tank which doesn't force me to wash my hands after every inversion.

Steve.
Click to expand...

I use a 2-reel Paterson (System 4) and the cover is tight. Never any leaks.
 
Agitate by inversion - and wear latex or nitrile gloves to avoid getting the chemicals on your fingers.
 
My Paterson System-4 tanks don't leak either. There are a lot of older Paterson tanks (with screw tops, white plastic lids etc) which are so old now that the original soft plastic seals are either hardened or missing - perhaps it is those that people have problems with? Anyway, the 'tupperware lid' style tanks work fine for me.

Inversion agitation also seems to give better agitation, if there is enough air volume in the tank to let it work. That could be tricky if the developer is highly diluted and you need a large volume to hold enough active dev, but possibly in that case one would be (somewhat optimistically) trying a variant of stand-development and using minimal agitation.
 
Mind you, there is the current (Tupperware lid type) Paterson Super System 4 and the older (screw-on type) 'non-super' System 4.

IME, the older system leaks almost invariably, while the latest version does not, or only if you let too much pressure build up (easily released).
 
Tea Leaves are good for this sort of flow visualisation - I have used them many times at work to try and understand water flow behaviour.

If you think about it its not surprising that constant uniform rotation does not agitate the developer - there is almost no relative movement inside the tank between the surface layer of the film and the chemical.

What agitation is supposed to achieve is to remove the depleted surface layer of developer with fresh chemicals.

Whether you use a flick of the "Twizzle Stick" or use inversion, the effect is the same, lots of relative movement between the film and chemical - allowing fresh chemical to replace the stale layer at the film surface.

On the subject of Paterson Tanks leaking, I have just invested in some new Paterson Tanks and have been pleasantly surprised how leak resistant they have been.

However, I still wear Nitrile Rubber Gloves - a friend after many years suddenly developed an allergy to Metol, which is a common component in many B&W Developers.

He nearly had to give up Photography because of it

Martin
 
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