Discolored streak down negatives

[sean_fitzgerald1]

In my school darkroom, some classmates and I have been getting

discolored streaks down the center of our negatives. It only happens

sometimes though, and to different people every time. It's happened

with Illford and Kodak films alike. We use d76 1:1, "standard kodak

acetic acid stop back" and "standard kodak fixer"... "both mixed

accordingly" according to my teacher. Agitation is done with

spinning rods. I agitate what I consider to be normally: (developer:

5 seconds every 30 seconds, fixer: 10-15 seconds every minute for 10

minutes) The developer is always between 19-21 C and recommended

times are mostly always used for developing. When we take the

negatives after they've been washed and put them back into the fixer

for about 5 minutes, the streaks go away... So I'm guessing that 10

minutes is not enough for the fixer? This is a few minutes more than

the recommended though, so I do not understand. Perhaps it is the

spinning agitation?

 

The tri-x negatives always come out a light transparent blue/gray

color. (this is normal, correct?) The streak going down the middle

is usually a pale yellow color. I made a print from one today before

I fixed it again. I noticed on the print that where the streak was,

there occurred a less amount of contrast and brighter values. I

apologize if this is a repeat, or obvious, but I could not find it

anywhere.

[bob_mcbob]

Bad fixer?

[ronald_moravec1]

In sufficient agitation in the fix. Spin rod agitation gets new solution to the edges, but not the center.

 

The proof is to cut off some and refix in a tray. The streak will disappear.

 

Agitation is to be vigorous and random so as not to set up any patterns.

 

A one reel tank (stainless steel) needs five inversions every 30 sec. Rotate 90 degrees when setting it down.

 

I use a two reel tank for one film with an empty reel on top. Fill with only enough to cover the bottom reel with the film. Rotate when setting down. Two easy inversions are sufficient.

 

A plastic Patterson tank has lots of head room so two inversions are ok. Use twist rod only for first agitation cycle if you read the instructions.

 

Your developer is off too with dense edges and less dense center. It will print light on the long dimension after you clean up the fix.

[chris_waller]

I'll also go with insufficient fixing. I use Paterson tanks and agitate by inversion. When I get to the fixing stage I agitate continuously. Within reason it's almost impossible to over-fix. I suggest you test the fixer by dropping the cut off leader of the film in a sample and then agitating it. Note the clearing time and fix for TWICE that.

[steve_unsworth1]

I use inversion for the fixing stage. Invert repeatedly for the first 30 secs and then 4 inversions halfway through the fixing time. 10 minutes should easily be enough provided there isn't a problem with the fixer.

[colmmccarthy]

Insufficient agitation. Spinning's no good. You need to invert those tanks and agitate better.

[kaiyen]

I fix with _constant_ agitation via inversion for 4 minutes each, 2 baths. That might be a bit of overkill, but I don't think that agitating more is going to cause any problems, and agitating not enough leads to fogginess/milkiness, plus possibly more of that purple tint action.

 

allan

[sean_fitzgerald1]

Well, if spinning is insufficient for fixer, is it insufficient for developer as well? Should I switch to inversions ?

[johnmarkpainter]

Sean,

 

Spinning isn't insufficient for anything. I never Invert my Tanks (Mostly Patterson).

 

Do a search of this Forum for "Minimal Agitation" it is a Technique. If you OVER Agitate in

the Developing stage it will change the way your image looks drastically.

 

The Fixer in your school Darkroom is either not mixed correctly or it is Spent. It is likely

that students aren't rinsing their Film well before the Fixing stage.

 

The Streak you are describing is when the Film hasn't "Cleared". You should try mixing

YOUR OWN batch of Fixer and don't let anyone else use it. Your troubles should be gone.

 

Oh yeah....you know it wears out, right?

 

jmp