If you don't neutralise the developer carry over that will help take the fixer more alkali and effectively you'll have a more than a trace of development taking place as the fixer's beginning it's task of dissolving unexposed and undeveloped silver halides. This can result in dichroic fogging - a patchy stain.
It's even more likely to happen with prints with no stop bath whether acid or alkali/neutral fixers but at least with a print you can make another once a neg is ruined it's gone
Then there's the ammonia smell as well
All fixers contain Sodium Sulfite or a Sulfite salt. On the acid side, this releases the very smelly SO2 (Sulfur Dioxide) gas which some people absolutely despise. Some are even allergic to it. On the alkaline side, Ammonium Hypo based fixers release Ammonia gas as the pH rises due to developer carryover (less so if you use a good running water rinse or an acid stop).
So, it depends on what you dislike most! SO2 or NH3... Take your pick. The happy medium is a near neutral pH fix at about 5.5 - 6.8. This does not release gases to any appreciable extent unless mishandled with a poor workflow.
AFAIK, no Kodak or Ilford film or paper needs a hardening fix, all of which are acid and use alum, or which are alkaline and contain formalin and no Ammonia. Recent reports say that some Fuji films may need a hardener. Many European films benefit from a hardening fix. The only way to know for sure is trial and error.
At the present time, I know of no neutral pH hardening fixer.
Any fix containing Ammonia is up to 10x faster than an all Sodium based fixer. Do not add Potassium salts or Calcium salts to a fixer.
There's a lot of bull-shit about alkali fixers most aren't Alkaline at all, someone seems to have tried to reinvented the definitions of Acid & Alkali.
pH 7 is neutral, most Alkali fixers are pH 5.6 - 6.8 according to one online test - that's acidic
Now how can a sub pH 7 fix be alkali but that's the claims
The only essential ingredient in a fixer is thiosulphate. All the rest is secondary, being preservative (primarily) and pH adjusting, and perhaps hardening. Rapid fixers are ammonium thiosulphate. If they are acidic they smell of SO2. If they are alkaline they smell of ammonia. If they are close to neutral (i.e. between acidic and alkaline) they have minimal smell. If you use materials from mainstream companies you don't need hardening, so use something like Kodak Flexicolor Fixer (pH=6.5) which is cheap, rapid and not very smelly. It's sold for color procesing but is totally functional for b+w fil and paper.
Originally Posted by Ian Grant
This is the kind of rubbish some manufacturers attribute to their "alkali" fixer.
1 Alkali fixer regulates the pH level of the development process.
As development takes place before fixing that's just not possible.
2. Alkali fixer will maximise the tanning and staining qualities of staining developers.
Again no fixer can add anything to the tanning or staining properties. If anything the more alkali a fixer is then the more softening of a tanned emulsion in the fixer bath. Strong acids may reduce the stain created during development but most commercial fixers are pH 5.2 to 6.5 and have no detrimental effects.
3. Alkali fixer has a much greater capacity than acid fixers
Capacity isn't directly related to pH and for archival permanence fixers aren't used to their full potential capacity.
Another manufacturer/supplier compares their Alkali Rapid fixer to "conventional Sodium Thiosuphate (Rapid) fixer", but Rapid fixers are based on Ammonium Thiosuphate so the data sheet does make you wonder how much of it is correct.
There's little or no odour with most Ammonium thiosulphate based fixers between pH 5 and 7, below pH 5 the sulphur smell increases higher than 7 and ammonia becomes noticeable.
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This bit of info is new to me: "AFAIK, no Kodak or Ilford film or paper needs a hardening fix, all of which are acid and use alum, or which are alkaline and contain formalin and no Ammonia. Recent reports say that some Fuji films may need a hardener. Many European films benefit from a hardening fix. The only way to know for sure is trial and error."
I've stopped using Tri-X sheet film since they changed some years ago, found it disappointing. Prior to that, I started using hardener after I got reticulation when my wash temp fluctuated. It didn't fluctuate that much, from cold to warmish, not hot, but it reticulated severely. I'm using T-Max - 400 now, with hardener. I wonder if I still need it? This is a great thread, BTW.
Tmax 400 along with Fuji Neopan 400 is one of the films that can suffer reticulation, although not as a badly as the Fuji film. However it's not quite so simple as it's a developer pH/formulation issue along with the temperature deviations that cause the problems.
In a separate thread I brought up this issue, developers like Rodinal with it's high Hydroxide content and some using Carbonate can soften certain emulsions more than devs like D76/ID-11, Xtol etc.
I used Rodinal for about 20 years and switched to Pyrocat HD about 5 years ago but I've not had an issue with my own negatives and I have used Tmax 400 both old and new and the Neopan 400, I've always used unhardened Hypam or Ilford Rapid fixer. However I have seen this reticulation first hand (someone else using my chemistry etc) and there are plenty of reports of it from other people.
At it's worst the reticulation of the Fuji film is full blown reticulation - cracking of the emulsion surface, but with the Kodak films it's milder and restricted to the surface, this is known as micro-reticulation or surface reticulation, although Kodak don't use the term, it causes increased graininess of prints or scans. The grain structure of the film isn't changed it's the effects of the gelatin surface, it can be worse with 120 films as they often have a gelatin anti curl layer on the back and this can suffer micro reticulation as well.
Ctein wet mounted his negatives for printing to get the finest grain and sharpness and I've found references and an article showing similar techniques being used as far back as the late 1920's to get finer grained prints with 35mm negatives.
In recent years Kodak have changed their hardening techniques to overcome this gelatin surface issue as it becomes even more apparent when negatives are scanned and this is why they now state many of their newer films scan better.
If you maintain reasonably tight temperature controls then a non hardening fixer is fine with all the B&W films manufactured today.
Last edited by Ian Grant; 07-01-2011 at 02:17 PM. Click to view previous post history.
Reason: change date to 1920's
Originally Posted by john_s
I said most of this in an earlier post with one notable exception. Most commercial fixes are not a single ingredient. And, they ALL contain Sulfite while most contain Ammonia. Therefore there is odor at either end of the pH spectrum, namely 4.5 or 8.0 approximately. The ideal is between about 5.5 and 6.8.
AFAIK, both Tmax and Trix use the same gelatin and the same hardener and therefore should respond about the same to temperature variations. Kodak has processes for these up to 90 degrees IIRC. Sometimes, very soft water coupled with extreme changes in temperature may cause problems, but it should be about the same for either film all other things being equal.
Just to clarify, is this just for modern Kodak & Ilford products?
Originally Posted by Photo Engineer