Inherent advantages of Alkali fixers?

[Tom Kershaw]

Are there any advantages of alkali fixers purely as a result of the alkali solution? i.e. can the features of an alkali fixer be designed into a fixer at <7 pH?

Tom

 

[Ian Grant]

A fixer like Hypam/Ilford Rapid Fixer etc is pH 5.2-5.4 that's not as acidic as a cup of Black Coffee at pH 5, many stop baths are around pH 2.2 - 2.5

The recommended throughput of some Alkaline fixers is less than Hypam, and the recommended wash times similar. If you're using a toner there's probably no real advantages at all, as the pH of the toner is going to come into effect.

Sandy King has indicated that the Ilford fixers are fine with Pyrocat negatives, and you might save on wash-aid (Sodium Sulphite) using an Alkali fixer but that maybe out weighed by higher costs.

Choice of alkaline fixers is more limited in the UK, so mixing your own is a good option.

Ian

 

[Tom Kershaw]

I've just come to the end of my stock of Fotospeed FX40, an alkali fixer, but one for which little or no documentation is available. For my standard printing I've been using Champion Amfix, and I'm in the process of considering whether it is worth pursuing another better documented Alkali fix (e.g. TF-3) or not.

Tom

 

[Photo Engineer]

Yes Tom, the features of an alkaline fixer can be designed into a fixer at a pH of less than 7. The trick is to design in comparable swell that is induced by alkali in the alkaline fixer. Then you have an acidic fixer with high swell and the high activity and wash rate of an alkaline fixer.

An acetic acid stop bath should be around pH 2.5 - 3 at 1 - 2% or when buffereed with sodium acetate about 4.0 to prevent undue damage to a photo product.

All of the testing was done years ago when Kodak first began selling alkaline fixers and the published data from those tests proved that the claims for alkaline fixes was true regardless of what the individual was doing with the fixer, selling or not. Early uses were in rapid X-ray processing and in color processing (Process P-122 and Ektaprint C come to mind). It is based on the gelatin swell profile as a function of pH which I have posted before, and it can be shown that by shifting that profile a fast fix / wash cycle can be achieved at any pH. Use of pig gelatin, which inverts the swell profile, inverts the fix / wash cycle to some extent all on its own.

So, it is not hype that alkaline fixes give enhances to the fix and wash and this effect can be achieved a variety of ways.

PE

 

[BobNewYork]

I've been using Champion minilab ammonium thio. fixer for years - apparently with no ill effects. I buy in bulk from Unique Photo and dilute it 1+4 for both film and paper. I run 20 "8x10 (or equivalent)" films in 1.5 litres. I've standardized my fix time to 10 minutes because testing showed a three minute clear time after 20 films. Washes easily out of fibre-based paper and as for RC you only have to show the print a running faucet from 30 yards!!!

Bob H

 

[dancqu]

Are there any advantages of alkali fixers purely
as a result of the alkali solution? i.e. can the features
of an alkali fixer be designed into a fixer at <7 pH? Tom

If you include neutral then either sodium or ammonium
fixers are much easier to mix. Spoon up or pour out
using the necessary volume of water. Nothing
need be added.

That's one feature you'll not design into an acid fixer.
Fresh fix is a breeze and either are odorless. Dan