The Darkroom Cookbook Forum

Hi Guys,



The TF-2 alkaline fixer formula given in the Cookbook uses Sodium Thiosulphate, a conventional fixer. It is recommended for modern tabular grain emulsions to use a rapid fixer. As with acid fixer recipes, is it possible to add ammonium chloride 1 part to every 4 parts hypo to make this into a rapid alkaline fixer?



The reason I ask is that in Australia it is very hard to find Ammonium Thiosulphate whereas Sodium Thiosulphate is commonly available. Also I don't know where you can get an off the shelf alkaline rapid fixer here in Meblourne, Australia.



Regards, Simon.

you probably already tried it by now. fwiw, i just got hold of a Kodak manual & in it there's a formula for Kodak rapid fixing bath F-7

Hypo: 360gr
Ammonium Chloride: 50gr
Sodium Sulfite: 15gr
Acetic Acid 28%: 48cc
Boric Acid: 7.5gr
Potass Alum: 15gr

But i'd omit the alum & boric acid, assuming they're just hardener. the acetic is part of the hardener, too, but it helps to reduce pH so ammonia doesnt escape from solution. In my experience, replacing the acetic acid with citric gives me the best self-mixed rapid fixed. I've a problem getting ammonium thiosulfate as well. price is too steep.

These are interesting questions and will be dealt with in Film Developing Cookbook 2.

Certainly, you can, and one might say should, add ammonium chloride to TF-2, but I would then worry that the pH would be high enough to cause ammonia fumes to emit. Therefore, I would suggest omitting the Kodalk. The target pH should be 7.2 to 8. I think you will be there comfortably, so long as you don't use an acid stop bath and carry it over into the fixer.

Regarding modifying F-7, you shouldn't remove the boric acid, which has an important role to play, because it extends the pH range under which the hardener, potassium alum, can be used. However, if you omit the potassium alum, you have a great deal more flexibility, and could reformulate F-7 to anywhere between pH 4.5 up to about pH 8. You could go higher, but not with open trays, as there would be too much ammonia smell.

Thank you for the response, Bill.