Weird streaking with 120.

[hamradio]

For some reason lately, I've had this weird issue with streaking across an outside edge of only a the first couple frames that get wound into a roll, on 120. I'm not doing anything crazy, usually doing two gentle inversions every 30sec, and agitating a few times when fixing as well. For a while I thought a back of mine may somehow be problematic, but it this is definitely a developing issue, as the same thing happens across multiple cameras.

Any ideas what might be going on?

 

[brainwood]

Wondering if it's a stress mark from putting the film on the spiral though it looks a bit far from the edge for that. Did you have any difficulty getting the film on the developing tank spiral ?

 

[newsgrunt]

does it only appear in that corner of the frames ?

 

[Dwig]

Dark on the positive image means light/clear on the negative. That means:

• less/no light in that area during exposure = something in the camera blocking light

or

• less/no development in that area = ?? possibly the film is shifting on the reel and the image area is coming in contact with the reel ??

 

[swifty63]

Yes I sometimes get this exact thing on 120, when developed in my Paterson tank and even in my SS tank. It is due to insufficient volume of developer in the tank, so that stop strip is not fully developed. Sometimes it appears as a series of blobs along the top of the frame.
Slight frothing in the developer causes cause bubbles at the top of the solution which impacts development by "starving" some portions at the top of the frames.
It was most annoying to get this! Add a little more developer, it should not happen then. Also gently invert, but you said you are already doing this so that isn't the problem I guess.
With the fixer, I agitate to my hearts content, it won't have any detrimental effect, all it is doing is removing the residual silver salts.

 

[swifty63]

To be more precise, when I said "add more developer", i meant volume of developer. When I look at the volume of developer solution required to cover to the top of the reel, I allow room so that the base of where those bubbles form (they always form to some extent), is above the top of the film. An extra 50 ml did the trick for me.

 

[Bob T]

I used to get similar effects with 120 then I changed my agitation routine to one full minute initial agitation and 10 seconds per minute after that. No further problems.

Good luck!