Continuation of... Developing without chemical stop...etc

[wdavidprice]

Nobody responded to Ole's suggestion...

 

"For the ultimate in darkroom simplification, add 30ml of rapid fixer

concentrate to the tank at the end of development instead of a

separate fix step. So that's dev, add fix, dump, wash."

 

I think this would be great...if it works...especially for traveling.

Has anybody else tried this technique?

[ivan_dzo]

There have been numerous recipes through the years for single bath developers ie developer, stop and fixer in one go. As you say it was used by travellers and people in a hurry. Difficult to get just right though as the developer has to be very quick acting to work before the film is fixed. Little advantage to separate developer and fixer. It's really not that difficult!

[chris_waller]

My concern about the process suggested would be dichroic fog. I would use a water rinse instead of stop to wash out the dev before fixing.

[rowland_mowrey]

Grant Haist has written the definitive book on the subject of Monobaths.

 

This is what you are really describing, a monobath. It works but the problems inherent in the process are so great that it has never been commercialized. People still use it on a one-shot basis.

 

Ron Mowrey

[jay_de_fehr]

I think there'ds a distinction to be made between converting a developer to a fixer after development is complete, and a true monobath. Ole is suggesting the former, and Ron is commenting on the latter. Pat gainer, among others, regularly adds ammonium thiosulfite after the development cycle. I think his procedure is to dump a small amount of the spent developer, and replace that volume with undiluted ammonium thiosulfite.

 

True monobath developers, Like Haist's, are very film-specific. By that, I mean that the formula must be adjusted to suit the particular film and desired contrast, and the approach is probably better suited to some films than to others. Some monobath formulae spec some pretty exotic chemicals, as well. All that being said, monobath development is on my list of things to try.

 

 

Jay

[ole_tjugen]

That's correct - I convert (spent) developer to an alkaline fixer by adding ammonium thiosulfate after development is done.

 

A monobath process is something entirely different, where the development and fixing occur simultaneously. I have tried it with moderate success, but it needs a lot of experimentation to find the best composition for each and every film.

 

In a way it was my dissatisfaction with monobath that led me to the "conversion" routine. I mostly use one-shot developers, and usually at dilutions high enough that the developer is essentially dead at the end of the development. Since the rest of the componenet in the developer are about the same as in my (own) rapid fixer, I decided to try just adding the thiosulfate to the spent developer and giving the tank a good shake. I haven't run any "time tests" on this, but I opened the tank after five minutes and the film was completely cleared. So I let it sit for an additional five minutes just to be safe.

 

What can I say? It works! You could even consider "pre-packing" little 20g bags of (dry) ammonium thiosulfate. Dilute in a shot glass, pour in the tank when development is done.

[richard_trochlil]

Back about 1960 or so, you could buy a commercial monobath, oddly enough I think it was called 'Monobath' and probably made by Edwal.

[robert_marvin]

IIRC it was called Unibath. There were two versions giving different film speeds. I used it when i first started to develop film c. 1958. Not bad stuff, but I quickly learned that conventional developers wweren't that much extra trouble.

[wdavidprice]

Ole...I would like to give this a try. I use a one shot developer of HC-110 diluted 1/63 for 9 to 13 minutes depending on temp for tri-x. My understanding is that the HC-110 is mostly spent by that time. Is your 20g dose of ammonium thiosulfate right for 1 roll of film?

Where does one obtain ammonium thiosulfate in dry form? I there a commercially available fixer that would have the same effect?

[ole_tjugen]

I buy my chemicals from www.vwr.com, but that's because they are the only source for chemicals in Norway. And the cheapest form of ammonium thiosulfate from there is dry anhydrous.

 

"Rapid fixer" concentrates tend to be 60% ammonium thiosulfate with some added sulfite and pH buffering chemicals, I would assume that 40ml TF-4 (conc) contains about 20g ammonium thiosulfate. The "milkyness" of TF-4 disappears quickly, so it isn't even necessary to dilute it further.

[patrick_gainer]

I add an amount of TF4 concentrate equal to 1/8 the amount of the developer at the end of development time. If necessary, I dump that much developer before adding the concentrate. It is by no means a monobath developer. I see absolutely no difference in negatives done this way and those done by the usual method of dump, stop or rinse, fix. The fixer, even though it is alkaline (you can also use acid fixer concentrate) apparently stops development quickly.

 

Many years ago, Edwall suggested this technique for use with their ammonium thiosulfate fixer concentrate.

 

So, for 16 oz developer, develop for usual time, dump 2 oz and add 2 oz TF4 fixer concentrate, fix for normal time. You can get by with 1 oz if you extend fixing time. You can inspect the process soon after you mix in the fixer.