Shelf life of Kodak hardener

[skipcress]

Some context: I recently bought some Kodak rapid fixer, which comes with hardener. Since I only plan to develop film, I plan to always use the fixer with the hardener.

As fixer only lasts about a month after opening, my plan is to pour it into smaller airtight bottles so it’ll last longer. My question is: should I premix the hardener in with the fixer (in the right ratios), or is that even necessary, i.e. does the hardener even break down due to oxidation? Because if it doesn’t, there’s no point in pouring it into smaller bottles (mixed with the fixer or not). And if I were to mix it in with the fixer, would that reduce the shelf life of the mixture, i.e. does the combination of the two elements not last as long as the two stored separately (I doubt it, but figured I’d ask)?

I’ve tried contacting Kodak on this several times, calling several different numbers and emailing several different email addresses, but never got ahold of a human, or received a response.

Thanks in advance!

[Larry Gebhardt]

I can’t answer your shelf life question. But the general consensus is that most films don’t need hardener, so it’s best to not use it since it makes washing much harder.

[koraks]

AFAIK the hardener used in applications like these is potassium alum, which requires an acidic environment to perform its job, so it's used in acidic fixers. In dry form it keeps virtually indefinitely.

[jnantz]

I can't remember but I think the only films that have a unhardened emulsion nowadays that might require hardener so they don't get damaged are / used to be Efke films. (Maybe Adox and Foma films are soft to being from Europe?) The other thing that might require you use hardened fixer or just a hardening bath are the sub layer and maybe emulsion layer of dry plates but you didn't mention you were making glass images. In most cases, as Larry pointed out, hardener is more of a pain than pleasure.

[koraks]

(Maybe Adox and Foma films are soft to being from Europe?)
I don't think there's necessarily a relationship between provenance and hardening. It's mostly a product-level decision with perhaps a brand/manufacturer tendency. Kodak appears to harden their emulsions pretty thoroughly; Ilford does just about the same as far as I can tell. Foma's films are indeed generally less hardened, and/or perhaps they don't have the same kind of tough topcoat that other brands use. Haven't tried Adox. Foma films don't need a hardener btw, and AFAIK Efke films did fine without one too.

[Michael R]

That's generally how it works. In the case of Kodak's rapid fix you get part A which is a standard acid rapid fix but buffered to allow the addition of part B (hardener) if desired, which is a solution of aluminum sulfate and sulfuric acid.

The shelf life would be similar whether stored separately or mixed.

I would generally agree under most circumstances you don't need the hardener, which also lengthens fixing and washing times. Ilford used to make a hardener you could add to Hypam (which is otherwise the same as Ilford Rapid Fixer) but no longer does and generally advises against using one with contemporary films.

Certainly with Kodak, Ilford or Fuji films, a hardening fixer is unnecessary. Other brands may or may not be less robust, but it's not like a hardening fixer will make up for sloppy handling of negatives anyway. It also obviously doesn't guard against damage before fixation.


AFAIK the hardener used in applications like these is potassium alum, which requires an acidic environment to perform its job, so it's used in acidic fixers. In dry form it keeps virtually indefinitely.

[skipcress]

Thanks, everyone! You’re retire replies have been EXTREMELY helpful!

[Duolab123]

Thanks, everyone! You’re retire replies have been EXTREMELY helpful!

I still use Kodak rapid fix with hardener for fiber base prints that I dry on a old fashioned drum dryer. No need for hardener with film or paper, exception being as I mentioned, toners that can soften the emulsion on prints, or tropical conditions.

Modern films are amazing, factory hardened.