I'm confused about alkaline fixers!

[michael_schiller]

Hi All.

 

I've decided to look into alkaline fixers, and I'm kind of confused. I've been using Kodak

Flexicolor fixer (I have a few gallons of it), and when I first started using it with Arista's

EDU films, they were scratching really easily, and the fixer was turning purple (the exact

same shade as HCA turns). I got a bottle of Rapid Fix Part B (the hardener) that I've been

adding to the fixer, and that's taken care of both problems, the film isn't as soft as it was

before, and the color stays more like it should (turns yellow as it gets used, not purple).

 

I reciently bought some sodium thiosulfate so I thought I would try making an alkaline

fixer with it, so I used the formula for TF-2, and it seems to work great, despite what

some folks think about needing ammonium thiosulfate for 'modern' films.

 

I looked up the pH of the Kodak flexicolor fixer, and find that it's 6.5 which is closer to

neutral than most other commercial fixers, so I was wondering why it made my film so soft

when used without the hardener? Would it be possible to make it more alkaline by adding

either sodium sulfite, or borax to it? If so, would there be an advantage?

 

As a side note, the batch of MC-TEA I mixed up seems to work pretty good!

 

Any comments about the fixer would be appreciated.

 

-Mike

[ronald_moravec1]

I have been using Photographer`s Formulary alkaline fix or years now.

A gallon is $20 and I shake it up and put it in four quart bottles the first time I open it.

 

Works fine with Delta and Tmax films.

[conrad_hoffman]

There should be a huge discussion of this in the archives from a few weeks ago. Also, I seem to remember that A&T *may* have had an error in one or more editions for the fixer receipe- be sure to double check this.

[rowland_mowrey]

Mike;

 

An alkaline fix with sodium salts is considerably less effective as a fix than a fix with ammonium salts. Alkaline fixes can have a strong odor of ammonia if made with ammonium salts. This is a bad feature to some. Many fixes today are near neutral (about ph 6.5).

 

I posted a URL to the swell profile of gelatin in photographic materials as a function of pH a few months ago. Swell is lowest at 4.5 and increases rapidly with pH, but swell and hardness are sometimes not related. See my other posts on this. Basically, a swollen soft film will fix more rapidly.

 

Generally, films from major manufacturers such as EK, Fuji, Ilford, and Agfa are hard enough to survive a process with no hardener, but other mfgrs often do not harden their films to the same point as these companies do.

 

If you wish to harden a film, do not use an alum hardener in an alkaline fix. It will cause a scum to form. Sodium Sulfate (note the spelling) at 100 g/l in a fix at any pH will decrease swell, slow down the fix, and wash out during the wash stage. It does not harden the film, just reduce swell.

 

The color of a fix or any photographic solution is often a function of pH as the dyes washed out often change color with pH. They also wash out of the film at different rates as a function of the pH. This is not a problem as long as you wash or otherwise treat the film long enough to remove the colored dye.

[michael_schiller]

Thanks for the replies, but I'm still curious, if I want to take my C41 fixer that's at a pH of

6.5 and raise it up to 7.5 or so, what would be the best chemical to do that with?

 

-Mike

[photojim]

Sodium thiosulfate might *seem* to be fine, but you won't know for a few decades. The final answer isn't in yet, but Kodak research suggests that sodium thiosulfate can't properly fix modern films because of the silver iodide content of the films. Older films had little to no silver iodide and fixed fine in sodium thiosulfate. To me, it's not worth the risk to see if Kodak was wrong.

[rowland_mowrey]

Mike;

 

If you want to raise the pH of C41 fixer to a higher value, use household unscented ammonia (ammonium hydroxide) that you can purchase at the local supermarket. Be sure it contains only ammonia. It should be added dropwise with stirring while you monitor the pH change.

 

It will work fine. It will also give a rather strong odor to the fix. But then any alkaline fix with ammonium salts will have an odor of ammonia to them.

 

The alternative is to use sodium carbonate or sodium hydroxide as solutions, adding it drop by drop. This will be effective, will still cause odor, and will slow the fix down a bit due to the sodium ion present.

 

Do NOT use any materials containing potassium. These can slow the fixing action down very much.

 

Ron Mowrey

[discpad]

Bingo!

 

Using C41-RA fixer explains why I had scratches on a batch of four rolls of Efke.

 

RON: Would I do better to raise the pH with ammonia; or should I use a hardener (Fixer Part B)?

 

Thanks!

Dan

[rowland_mowrey]

Dan;

 

The C41 fix at any pH should be no better or worse than any other non-hardening fixer with most films. I have to assume that it is the Efke film that is underhardened. If that is the case, it will be soft and swollen in any nonhardened fixer.

 

You cannot add the standard alum hardener to any neutral or alkaline fixer, as the active ingredient is aluminum (alum) sulfate. This will ordinarily precipitate out and form scum at near neutral or alkaline pH. If you want to work at neutral or alkaline pH and harden, you will slow down fixing action by a rather large amount. In addition, the effects of the alum are only for the duration of the fix, and the first part of the wash, as the alum is not a permanent hardener.

 

The way to harden at alkaline or neutral pH (well, not harden really but reduce swell and scratching) is to add 100 g/l sodium or ammonium sulfate (note spelling) to the fixer.

 

Other true hardners for this pH range (~6.5 - ~9) include zirconium sulfate. This causes case hardening at the surface layer of the film and reduces swell. Another ingredient is formalin at about 3% in the fix. This does not keep well and I have not tested either of these in ammonium fixes, just in sodium fixes.

 

In general, the major manufacturers, having solved the bulk of hardening problems in flms and papers, have been tending towards neutral or near neutral nonhardening fixers. This started in the mid 60s.

 

Therefore, with Efke and similar films it might be prudent to use the old acidic hardener fixes for best results rather than play around looking for a good process. IDK. You will have to judge for yourself what is best for you.

 

Adjusting pH in ammonium fixes should be with Ammonium hydroxide and either acetic acid (28%) or citric acid. With sodium fixes, use sodium carbonate or bicarbonate or sodium hydroxide, and citric or acetic acid. This is for acid base pH adjustment and these chemicals should be handled with care. I list them in order of danger - worst to least worse - Sodium Hydroxide, Sodium Carbonate, Sodium Bicarbonate, Acetic Acid, Citric Acid. (alkaline materials are much more dangerous to human skin and mucous membranes than acidic materials)

 

Ron Mowrey

[discpad]

Ron, I'll follow your advice and get a bottle of conventional hardening fixer. What I'll do is use it as the second stage fixer, since I 2 stage fix anyway: C41-RA fixer, quick wash, hardening fixer, final wash.

 

Thanks!

 

Dan