Bubbles in the negatives

AgX

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Photo Engineer said:
The bubbles prevent wetting of the surface with active solution for just enough time to alter diffusion of solution. Therefore, marks appear.
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This hampering would be different after each turn. How then a defined structure could appear?
Unless there is a static layer of foam. For instance when the fluid level is far below center (at least one winding). Also the rotation direction may be off effect (Archimedes effect, shoveling fluid above level).
 

koraks

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The last 3 frames are closest to the center of the tank (especially with two 120 rolls end to end), which is also the top of the fluid level when the tank is placed horizontally.
 
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Dani

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The one with the most problem with bubbles was the third to the last frame. Pretty odd, I'm still puzzling over it.
 

Photo Engineer

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If the rotation was slow to start, or the tank was slow to fill, bubbles form and float to the top. I cannot explain it more, but it seems to me that bubbles are the basis for this.

However, it may also be irregular drying on the lowest frames when hung. Sometimes bubbles or "micelles" form. This can cause a similar effect.

PE
 
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Dani

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The jobo I’m using only has the 75RPM speed but maybe I was too slow to pour in the developer.

The film hang with those frames being at the top.
 

koraks

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You pour in developer, tilt the tank, attach it to the jobo and then start the motor - there's a small time frame when the tank is horizontal but not rotating. I think that's what PE is getting at. I can imagine that under some circumstances, this may yield the phenomenon you are experiencing.

FYI: I personally always do the final rinse/conditioning in a tray after taking the film off the reel. That way I get no surfactants on my tanks and reels. Previously this didn't give me problems, but I get a feeling that your mishap illustrates why this approach may be a good idea.
 
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Dani

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My jobo has a lift, so the tank is rotating all the time.

I’m going to develop some film over the weekend and I’ll report back.

Thank you all!
 

MattKing

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koraks said:
The last 3 frames are closest to the center of the tank (especially with two 120 rolls end to end), which is also the top of the fluid level when the tank is placed horizontally.
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Unless they are the ones closest to the edge of the tank - if you load the film into the reels the way I do.
 
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Dani

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I just checked and those three frames ended up being closest to the center of the tank.
 

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Photo Engineer

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And the center is where the solution flows out into the tank as you pour it. This may be the cause of the bubbles. Surfactant present or some such effect causing bubbles.

PE
 
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Dani

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Is there a way to effectively remove the surfactant from the tank and reel?
 

koraks

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Wash thoroughly. Eventually it dilutes so far during repeated washing as to have no consequences. You'll notice that after a few changes of water the foaming subsides.
 
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Dani

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Great! I’ll try that again and again. Thank you!
 

AgX

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Dani said:
Is there a way to effectively remove the surfactant from the tank and reel?
Click to expand...

The residues of final rinse inside the tank got the concentration of that final rinse. With the tank filled up with a new bath one may estimate the volume of that residue and calculate its new concentration... I consider the effect of such residues overestimated.

One might do a test with a plain water bath, once inserted into a non-washed tank after final rinse and once after washing that tank, and see for foaming.
 
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