is stop bath essential?
I've been developing using tap water instead of stopbath and the results are fine, but someone told me the negative keeps on developing unless i use stop bath.
does it keep on developing even after it's been hung out to dry???
fyi: i am developing 35mm 400 iso BW film with HC -110
I use water too - the acid stop irritates my lungs. The stop bath neutralizes the developer and stops the process. If you don't use it, the developing process continues until you pour in the fixer. It probably doesn't matter much if you have a reasonably long developing time, and you can compensate by shortening development time slightly. Also, I think the fixer will become depleted more quickly.
My understanding is that stop bath actually stops development more immediately than water does as the pH is lower. To some extent using a water stop does mean that there is still a minimal amount of development occurrring, but as long as you get the fixer in reasonably quickly, this should not matter. The film stops developing once it is fixed, so unless you forgot to fix it, it does not keep developing after it's hung out to dry.
In a word, "no".
You don't need stop bath. Even if any meaningful continued development occurred in the water rinse before the fixer, it would likely be accounted for when you establish your development times through testing.
Even better is to use an all-alkaline processing workflow, with alkaline developer followed by water rinse and then by an alkaline fixer, such as the Formulary's TF-4. IINM this is the recommendation of at least Ilford, if not Kodak also. More archival, since it rinses cleaner for a given wash time, and obviates the need for hypo clear.
No, but some people like it.
An acid stop keeps an acid fix acidic. Do you use and
Originally Posted by bessa_L_R3a
reuse an acid fixer?
Keeps on developing. Nothing more than a hint of water
bath development. Some go for it; two bath, the
B bath being water. Dan
I quit using stop bath with film several weeks ago. So far, so good. I just started "not using" with paper.
As everyone has pointed out, there's no need for an acid stop bath unless your development times are very short <5 mins. If development times are short then you need to stop development very quickly and that would require the acid stop bath. However, most of us are developing for longer times than that.
I would not advise dropping the acid stop bath for printing paper though. It helps keep the highlights clean. I think this is possibly due to the fact that paper develops very quickly and the highlights will begin to dull with over development.
Others have answered, but from your question I suspect you might want to get a clearer idea of what is happening during processing so you can make up your own mind.
Developers are alkaline and development can only continue in an alkaline environment. Dunking the film in an acid stop bath (no more acidic than table vinegar, so no worries about that) rapidly changes the environment to acidic which stops development almost immediately.
Fixer is (usually) acidic. Using an acid stop bath prevents the alkaline developer from contaminating the fixer (which needs to be acidic to work). So, when using an acid fixer, the use of an acid stop bath both arrests development rapidly and extends the life of the fixer. Two good things in one!
Using water, the development is not stopped so suddenly, slowing development down until it eventually is effectively stopped as the water dilutes the developer soaked into the emulsion over a period of several seconds. Is this amount of extra development time important? Probably not in the great scheme of things given all the other variables. To avoid contaminating the fixer, a few changes of water with agitation will probably be required.
However, if you use a non-acidic fixer (not so common, but quite a few people prefer them) then you would probably use a few changes of water and not an acid stop as the acid would contaminate the alkaline, or neutral, fixer. All these fixers, both acid and alkaline, (and neutral) will have buffering agents to reduce the effects of this kind of contamination but they will last much longer if they are not contaminated in the first place.
If you do not like the smell of most stop baths, you can use a citric acid based stop (most are acetic acid - as in vinegar - based). Ilford (Ilfostop), Fotospeed and Tetenal amongst others make them. These have no odour at all. They work out somewhat more expensive I think, but that is a small price to pay for no odour IMNSHO ;).
Good luck, Bob.
that's a heck of a lot of feedback ... I'm developing HP5+ and time is 5 minutes (Dil B) at 68 F using Ilford rapid fixer and my wash is just 4 or 5 water refills with increasing agitation frequency with each fill.
i guess by using water stop bath i'm extending the developing time minimally from 5 minutes upwards but unless i'm doing anything radically wrong in all this i'll just do it this way.