Are acetic acid stop bath and acid hardening fixer redundant?

[majid]

Since the main purpose of the stop bath is to lower the pH and desactivate the

developer, shouldn't acid hardening fixers do both in a single operation? Or is the

idea to also wash away the developer (in which case plain water would also do the

trick)?

[m0002a]

Acetic acid stop bath stops the development immediately and removes the alkalinity of the developer before fixing. But acetic acid stop bath is optional (can use water or skip entirely) since the fixer has acetic acid in it. However, in addition to immediately stopping the development, stop bath helps to extend the life of the fixer somewhat, since water alone does not remove all the alkalinity of the developer (unless you wash it for a while). The hardener is for a separate purpose, and even fixer without hardener will stop the development.

[conrad_hoffman]

The fixer will last longer if it doesn't have to neutralize the developer, and there is the possiblity of stains if you go direct from developer to fixer. Either use a weak acid stop bath, or a few changes of water. Hardener is another matter entirely, and there doesn't seem to be much reason to use it these days. OTOH, hardening fixer like Kodak powdered fixer works about as well as it ever did, and I still use it sometimes. A better solution (no pun intended) is Photographer's Formulary TF-4 akaline fixer. It's faster, washes faster, has better capacity, and maintains an akaline environment start to finish. Don't use acid stop bath with it, just a few changes of water.

[john_cook1]

A second purpose for the stop bath is to save wear and tear on the fixer, thus prolonging its life. I never took the time to work it out exactly, but a tray of indicator stop is cheaper than a tray of fixer.

 

While I'm here, let me recommend Ilford odorless indicator stop bath which is more pleasant to work with.

 

Also, Ilford no longer recommends the use of hardening fixer, as the hardener is unecessary with modern emulsions and also is difficult to wash away. A dandy fixer is Ilford Rapid Fixer which is sold in liquid form, works for both film and paper in the same strength, and washes away very quickly.

 

Check out the technical information in pdf form on their website at

 

http://www.ilford.com/html/us_english/homeng.html

[photojim]

Actually, Conrad, according to Steve Anchell in The Film Development Cookbook, there is some evidence that good old powdered fixer does *not* work as well as it ever has. There are more iodine compounds in modern emulsions than in older ones, and it seems likely that sodium thiosulfate (which is in powdered fixers) reacts with the iodine to form compounds that are very difficult to wash out of the film, no matter what the wash time. On the other hand, an alkaline ammonium thiosulfate bath (like TF-4) needs a very minimal wash time to be completely archival. I've switched completely to TF-4 for film as a result (although, due to TF-4's odour, the odd time that I do sheet film I usually use a standard acidic rapid fixer).

[conrad_hoffman]

Hi Jim. Yeah, I did read that, but just haven't seen or heard of any actual problems because of it. Possibly those problems are years away, and it's one of those time-bomb issues. Also, I think emulsions have always had some iodine compounds; the amounts and in what films are unlikely to be revealed to us, so it's sort of a crap shoot. I use TF-4 for all my films and am satisfied with it in every way. Most of my prints still get the old stuff.

[frank.schifano]

You're assumptions are correct, but as others have posted here, your fixing bath will last longer if you use an acid stop bath. I've gone through periods when I've alternately used, stopped using, and resumed using an acid stop bath for film. I found that I was able to squeeze at least a few more rolls through a batch of fixer before it expired. That advice goes double for prints unless you have a sink and running water in your darkroom which I don't have. And as others have also said, a bit of stop bath is certainly a lot cheaper than fixer. Some of the pyro developer formulae and Diafine recommend that you NOT use an acid stop bath. In those cases, I'll follow the manufacturers recommendation. No matter which you choose, just use some sort of hypo clearing agent (the brand is not important) before the final wash to be sure that all the fixer and byproducts will wash out. That stuff too, is dirt cheap, so I see no reason not to use it. It certainly will do no harm if used as directed.

 

The debates about hardening vs. non-hardening, rapid vs. traditional, and acid vs alkaline fixing baths are heated ones to be sure and I for one am not going to take sides in any of them. I tend to use whatever I can get at the best price when I need it. Traditional fixers have worked fine, with longer fixing times, even with the newer emulsions containing more silver iodide. More often than not, however, a partially used fixing bath will go bad on me from age before I've used it to capacity. The only exception I'd make here is if I want to tone a print after fixing. Then I'll use a non-hardening fixer. My experience here is limited to the use of two part, bleach/redevelop sepia toner but anecdotal evidence suggests that the bleaching process works more efficiently and completely without the hardener in the fixing bath.

[majid]

I forgot to mention this, but I was implicitly thinking in the context of film

development.

 

The conclusions I draw are:

 

- the stop bath is not strictly necessary but as it is cheap it saves on fixer and avoids

potential streaking

 

- many people advocate using a neutral water stop bath and alkaline non-hardening

fixers, i.e. TF4, the only commercially available product

 

I guess I will continue using my current stock of acid fixer until it is exhausted, and

then investigate TF-4, as "The Film Developing Cookbook" makes a very strong

argument for them, on the basis of faster washing and better archival characteristics

by avoiding acids altogether.

 

Thanks to all who responded. My next step - deciding whether I should switch from

Ilfotec DD-X to either XTOL or D76, but that's for another day :-)

[m0002a]

There is one problem with acetic acid used on film. It can cause pinholes with certain thin emulsion films when using a highly alkaline developer like Rodinal (and maybe others). Also, I don't like to store stop bath as a working solution and re-use it. Therefore, I mix it at 1/4th recommended strength as a one-shot (or one session) solution.

 

Use of an alkaline fix is not advisable for modern film emulsions, in my opinion. An ammonium thiosulfate rapid fix is strongly recommended for films. Alkaline fix can be used for paper.

[ole_tjugen]

"Use of an alkaline fix is not advisable for modern film emulsions, in my opinion. An ammonium thiosulfate rapid fix is strongly recommended for films."

 

Mark, you seem to be confusing alkaline with "Hypo". There are alkaline fixers with sodium thiosulphate or ammonium thiosulphate. I use one with both...

 

Anchell & Troop's recommendation was that "there are indications that sodium thiosulphate fixers may not work properly with some modern emulsions, and we therefore recommend ammonium thiosulphate ("rapid") fixers for all modern materials". Or words to that effect. They specifically recommend alkaline ammonium thiosulphate fixers...

 

My own favorite is TF2 with 3 teaspoons of ammonium chloride per liter. That gives it enough ammonia concentration to gain the "rapid" benefits, while being significantly cheaper (and easier to store) than TF4. The odour level is very low - I have smelled many acid fixers that are much worse.

[richard_urmonas]

Unless you are using a staining developer (e.g. pyro based) then

you should use an acid fixer. I researched this after reading

the "Film Developing Cookbook". Acid fixers prevent staining

etc. by removing unwanted developer products far more effectively

than alkaline fixers. I suspect this is why film manufacturers all

suggest acid fixers. As for washing, years ago I read research

which investigated rapid washing (for processing machines).

They found that it was possible to wash acid fixed film to archival

standards in just 15 seconds. I wish I could find where I had

read this. Anyway the Ilford washing method works, and is both

quick and water efficient.