Fixer and color tinted negatives

[photophorous]

Every time I read about this, I find a variety of opinions. I wish we could get a Kodak chemist to straighten us out, but that seems unlikely. Below is my understanding of the topic. Please comment, confirm, or disagree as you see fit.

The purpose of fixer is to remove the unexposed Silver Halide crystals from developed negatives. Improperly fixed negatives will have a cloudy look and will not be transparent. After fixing (assuming good fixer and proper times), your negatives should be clearly transparent, aside from a small amount of film base fog. The presence of a color tint does not necessarily indicate improper fixing.

Some films have various coatings such as antihalation layers, speed enhancing layers, and probably other proprietary layers that the manufacturers don't talk about. One or more of these layers is responsible for the purple, pink, or blue colors we see. Typically, fixer will remove these layers, but that is not the purpose of fixer. When fixer fails to remove the color tint, it often leads people to falsely believe their negatives are not properly fixed. It is possible that fixer becomes less effective at removing the color layers as it becomes exhausted, but this is not a reliable indicator of your fixer's effectiveness.

As long as you are sure you're using good fixer, and you follow the mfg recommendations, any remaining color tint should wash out with hypo-clear and a final rinse. If this doesn't work, try changing your washing methods before changing your fixing methods. If the film is already fixed, then fixing it again is really just using your fixer as a washing agent.

One thing that may help is a presoak. Try a 30-60 second presoak with water at the developer temp, and agitate. If you see a color tint when you drain the presoak water, you've already removed some of the color.

Paul

[Xia_Ke]

Good post Paul So far I've tried Ilford Delta 100, HP5, FP4, SFX 200, Kodak Plus-X, Tri-X, TMax 100, Agfa APX 400, and Fuji Neopan 400. The only time I have seen any sort of color cast was with the TMax and it was a light pink/purple. I hadn't done a fixer test for a couple rolls and it turned out to be exhausted. Also, I hadn't realized until into development that I had needed to mix up some more Hypo Clearing Agent and just rinsed with water. Subsequent rolls using good fixer and hypo proved fine. Needless to say I am no longer lazy when developing...LOL

What films have you experienced a color cast with? Under what circumstances did it appear? Did it effect the usability of the negatives?

[photophorous]

Hi Aaron,

I'm glad you joined in, because I'd really like to understand this a little better. I didn't mean to say that all films will do this, but most of the films I've developed had at least a little bit of color. Usually, I see color after fixing, but then the hypo-clear washes it out. If not, then I wash longer. I can only remember one time that I couldn't get the color out, and that was with Tri-X. That was before I figured out that better washing would take care of it. It was a long time ago. I could have had old fix too. :blush2:

Judging from what I've read and from what you're saying about your experience, I'm thinking a persons choice in chemicals might have a lot to do with it. I've always used D76, water stop bath, Kodak Fixer (not rapid), and Kodak Hypo-Clear. Tmax, TriX, PlusX, Acros had color, some more than others. I don't think Delta 400 had any color. All the Kodak films were pinkish, but Acros was sort of blue. I can't remember about Neopan 400, but I think it had some color too.

Paul

[Xia_Ke]

All the B&W films I have run have had varying degrees of color wash out. I can't remember how much or when it washed out with all of them but, Plus-X had a lot of dye that washes out with the developer, while Neopan 400 only has a little which washes out with the Hypo. What is the dye layer for anyway? Is it to adjust the red sensitivity and make them panchromatic?

[photophorous]

I don't know much about what the dye layers are for, but I think they usually serve multiple purposes. I think all films have an antihalation layer, that helps prevent the light from scattering and bouncing around inside the camera, which would cause the film to fog. It also helps to prevent scratches in the emulsion. Some films have layers that help to increase the film speed. You may be right about the panchromatic thing too.

What you mentioned about the color washing out is what I'm talking about. I think with different films and different chemistry, those colors get washed out at different stages in the process. There seems to be a misconception that this color is somehow related to fixing, but I don't think that completely makes sense. Sometimes fixer washes the color off, but not with every combination. Sometimes it just doesn't get washed out until you wash with hypo-clear or even during the final rinse. Of course, if you have a standardized process where the color is always gone after fixing, and all of sudden it's not, that might be a signal that something isn't right.

[Xia_Ke]

I have to thank you for starting this thread. It's made read and learn much more about how film is made. Here's a quote relating to dyes in film...

As naturally prepared, silver halide emulsions are very much more sensitive to blue and UV light than to green and red wavelengths. The German chemist Hermann W. Vogel found out how to extend the sensitivity into the green, and later the orange, by adding sensitising dyes to the emulsion.

[SmartWombat]

Anti-halation is just in the back of the emulsion, at the base/emulsion interface.
It's not going to stop scatter throughout the camera, but it does stop the important bit.

Think of it like the multi-coating on the lens elements.
From a point of light focussed on the emulsion, light can bounce back off the base and expose the emulsion a little way away from the origin.
But the anti-halation layer can reduce that light, twice, to make the haloes less intense.

[photophorous]

Anti-halation is just in the back of the emulsion, at the base/emulsion interface.
It's not going to stop scatter throughout the camera, but it does stop the important bit.

Think of it like the multi-coating on the lens elements.
From a point of light focussed on the emulsion, light can bounce back off the base and expose the emulsion a little way away from the origin.
But the anti-halation layer can reduce that light, twice, to make the haloes less intense.

Thanks for clarifying that, Paul. That's a good illustration.

[Xia_Ke]

Thanks Paul

[SmartWombat]

Thanks for clarifying that, Paul. That's a good illustration.

Thanks - comes from having both parents as teachers perhaps