2015 February 3    Film   Developing

Background


The fixer is one of the three critical steps in developing black & white film.  (The steps are: Developer, Stop Bath, and Fixer).

Dry powdered fixer is not really expensive, but sometimes you just want to mix up enough for a roll or two.

If you want the whole developing process to go smoothly, there are a couple things you should know about fixer.


A Quick Note


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In This Article


Basic Instructions

Diluting Fixer

Negatives Cloudy After Fixing?

When The Fixer Is Spent

Another Tip

Fixing Times

Conclusion




Basic Instructions


Kodak Professional Fixer is a dry powder.  It's a hypo-based fixer, with some other ingredients to stabilize it and make it fix more reliably.

The bag contains 700 grams.  You're supposed to mix this with 3 liters of water, for a total of 3.78 liters (one gallon).

The fixer can take a while to dissolve.  There will usually be clumps on the bottom.  They require swirling for several minutes.

How many rolls of film can you fix with this?

If you mix according to the instructions, it is supposed to be 100 rolls.  That's going to vary depending on 24 vs 36 exp, and also how long you store the fixer. 

As-directed, the fixer solution actually has a rather long shelf life (couple months).




Diluting Fixer


There is no point in mixing up 100 rolls' worth of fixer if you're not going to develop 100 rolls of film this month.

I shoot a lot of color, so for me, black & white is sort of "on again, off again". 

If that's you, too, you might want to mix up just enough fixer for one or two rolls at a time.

If 700 grams can do 100 rolls of 35mm film, then 7 grams should be able to do one roll of film.  Right?

Maybe not.  Here's why.

To use that 7 grams in a Universal tank, you would have to mix it with at least 300 mL of water.  That means your fixer will be 10 times more dilute than recommended.

That fixer will be useless in a matter of hours. 

I've found that even if you mix up fixer that's only twice as dilute as recommended, it will not even last for a few days. 

There is some well-known chemistry here.  When diluted, the active ingredient (hypo) more readily turns into something that cannot fix your film.  

If you mix the fixer according to the label, it will be concentrated enough to stabilize the solution for a long time. It could last for five or six months, if you keep it from air.

If you want to mix up some dilute fixer, mix it immediately prior to using it.   Keep the batches small, or it will go to waste before you can use it. 

If you're going to prepare more than you'll need to do 2 rolls right now (within the next hour), use the concentration recommended on the package.  That would be 70 grams of fixer per 300 mL of water.  In theory that should have enough to do 10 rolls of film.  Even in less-than-ideal conditions, you should be able to get at least half that many out of it. 

Five or ten rolls from 70 grams of fixer... or not even two rolls from 35 grams. Which is the better deal?



              



Negatives Are Cloudy After Fixing?


If your film has a heavy, thick fog that you can see in the light, your fixer might have depleted in the middle of the fixing process.  Quite often it won't cover the whole film. If it looks like cloudy film emulsion, that's because it is.

It happens because the film was not fixed completely.

One reason could be that the fixer was too dilute, or it sat on the shelf too long. 



The good news is that you can always re-fix the film.   (It seems to work better if you don't wait until the film dries out, though.)  I've read that the negatives won't be as archival as if you'd fixed them correctly the first time, so just keep that in mind. I don't yet know for sure the chemical reason for this; I wouldn't be surprised if oxidation had something to do with it.

I do know that silver halides can take a "set" if they're left out too long in the air and the light. They become much less soluble.

To your 300 or 350 milliliters of depleted fixer solution, add one more teaspoon of dry fixer powder.  Swirl to dissolve.   Then, pour the solution back into your film developing tank and let it stay there for 5 to 10 minutes. Swirl periodically.

The thick haze should be gone.  It was simply silver halide that didn't dissolve.




When The Fixer Is Spent


After a while, fixer becomes saturated with the silver that it removes from the film.  It's not silver metal, but compounds of silver.

Test your fixer solution periodically with some of this.  You won't have to do it for those 1- to 2-roll batches of dilute fixer, but if you mix up the whole gallon, I suggest using the tester. 




Another Tip


Most photographers test a small piece of film in their fixer solution, to get an idea of how long the fixing time should be. The rule of thumb: fix for twice as long as it takes to clear a piece of film.

You can use a scrap of film leader to do this. Even if it's been out in the light, it's still good for the fixer test. Save the pieces that you trim off when squaring the edge for the film reels.

One way you will know the fixer is working, if you are observant, is that you will notice a subtle color change in the solution. 

The silver complex that forms is supposed to be colorless, but it's not;  it's very light tan or brown.   This happens due to transformation of the complex into fine particles of silver sulfide.  I think it starts out as a colloid (i.e., it never settles out of solution.) 

There's a chemical equilibrium there.  It's pretty much a one-way reaction, though;  once you get silver sulfide, it stays silver sulfide unless you add a lot more fixer.   However, you wouldn't get any of this brown coloration if the fixer were not working. 



Fixing Times


With rapid fixers you can fix... rapidly.  Normally that will be less than ten minutes. Kodak dry powder fixer is not a rapid fixer. I like it, though, because some films are actually not supposed to use rapid fixers. You're less likely to go wrong with a traditional hypo fixer like this one.

Originally I figured on five to seven minutes with diluted fixer; however, I found this was kind of erratic. Some variable was making it work sometimes, and not other times. Those other times, the film would not clear entirely. By making the fixer solution a bit more concentrated and extending the fixing time to 10 minutes, it clears every time.

Don't forget to agitate or swirl the film.

Don't overfix the negatives. Too long, and it could actually start to dissolve the silver. The fine details would go away first. One advantage of diluted fixer is that it's less likely to affect the silver itself, in case you leave it in a bit too long.



Conclusion


This has been a look at mixing up fixer, both normal and diluted.

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