By fabricator4/Chris (3,505) 
on May 22, 2005 1:38:41 AM CDT
Introduction
Materials
Method
Analysis
Conclusion
Comments
Introduction
This was a test to determine what affect if any substituting a water wash for stop bath has on film development. Invariably when I recommend that a water wash be used someone says "Oh but you can't do that!". Supposedly an acid stop bath will "stop" the development but a water wash won't, or not as fast.
Materials
Two strips of FP4 film
Tray of Ilfotec HC mixed as a one shot developer (1:47)
Tray of Ilford indicator stop bath
Tray of very special H2O, right out of the tap at about 23C
Tray of Ilford Rapid fixer
Normal room light.
Method
I cut two short lengths of FP4 off my bulk roll, each about four inches long
In normal room light both strips were inserted emulsion down into the dev and given constant light agitation. Normal development time is 12 minutes. Originally it was my intention to give them three minutes development but they'd developed to a heavy grey at 2:25 so I picked up both strips and drained them for five seconds.
Each strip was then simultaneously inserted into it's respective stop solution:- one into the acid stop and the other into the tap water and were left there for one minute with intermittent agitation.
Both strips were then simultaneously removed from their solutions and dropped into the rapid fixer. Processing from then on was normal: 2 min fix, five minutes wash, photoflo final wash.
Both films were then dried and put on the Epson scanner for evaluation with the densitometer function. Five readings were taken from the middle area at various places along the length of each strip. These readings were then averaged and compared.
Analysis
|
|
1 |
2 |
3 |
4 |
5 |
Average |
|
A
|
236 |
236 |
239 |
237 |
236 |
236.8 |
|
B
|
239 |
236 |
238 |
237 |
235 |
237.0 |
All readings varied to some extent, which appears to be well within normal tolerances. The tonal range on both films is very similar and appears to be about the equivalent of a zone 8 exposure for this film, but is well short of the maximum density. The film was rapidly approaching maxium density however and it would be better to process for the equivalent density of a zone 5 exposure: try two minutes development next time.
Conclusion
Given the rapidity of the development the close results are fairly miraculous. The two strips were processed differently only in regards to the stop bath and it can be safely assumed that the use of water instead of acid stop bath has no measurable affect on the degree of film development.
NOTE: This test deals with film processing only. The use of acid stop bath on photographic paper processing is still highly recommended for reasons of convenience in the darkroom, and to counter the alkaline developer that will be absorbed in fiber based papers.
Comments
Read 4,839 times
Reply
|
From fabricator4/Chris (3,505)
on May 23, 2005 4:12:09 AM CDT
Thanks Willis, I'll have a look at tables, presumably via some HTML.
BTW I recieved no mail notification of your replies to the article, so I take that this is still to be added.
Reply
|
|
|
From fabricator4/Chris (3,505)
on May 23, 2005 11:33:44 AM CDT
I just did the data as a table. I have no idea if I did it right, since it's the first time I've ever done a table in HTML (seems a bit long-winded).
Reply
|
|
|
From joshfreeman/Josh (1,563)
on May 22, 2005 2:37:47 PM CDT
My large format photography teacher at college recommends this as well. He also said that a water stop will help prevent pinholes from forming in the emulsion.
Reply
|
|
|
From fabricator4/Chris (3,505)
on May 23, 2005 4:28:13 AM CDT
a water stop will help prevent pinholes from forming in the emulsion
Yes that's true. The alkaline developer in the emulsion can react agressively with the acetic acid stop bath, and pinholes can be the result. In practice it's not likely to be a problem though, unless you are in the habit of mixing the stop bath extremely strong. As long as you stick with the recommended dilutions for an acetic acid stop bath then it should be perfectly fine to use.
Citric acid (odorless) stop bath has some bufferring affect so it might not be so critical. It could be that the commercial odorless stop baths have an added buffer: my memory is a bit faulty on this one.
Reply
|
|
|
From vaidotas/Vaidotas (205)
on May 25, 2005 4:27:45 PM CDT
Thank you for your conclusions (I never use any acid for stop bath - luckily :)
More interesting and mistificated thing IMO is presoaking influence into film developing results. Maybe you have some figures on that?
Reply
|
|
|
From fabricator4/Chris (3,505)
on May 28, 2005 12:31:27 PM CDT
Pre-soaking would wet the gelatine, speeding up the start of development. It also has the effect of normalising the temperature inside the tank.
It's a great idea though, and would lend itself to daylight testing. The objective would be to show if there actually was a difference in development between pre-soaked and normal development.
Reply
|
|
|
From dalemarsh/Dale (1,081)
on May 27, 2005 1:35:12 AM CDT
Its been along time since I developed large amounts of film but it seems to me that one of the reasons for using an acid bath was to help keep developer out of the hypo. Water still leaves alittle residue carry over. this means that we had to repalce the hypo bath more often. And with lage amount of film that gets expensive.
Reply
|
|
|
From fabricator4/Chris (3,505)
on May 28, 2005 12:45:26 PM CDT
This is true for paper development, and is the reason I recommend that acid stop bath be used for paper in the darkroom. For film there is very little contamination of the fixer since normal procedure for stop is a one minute wash which is enough to remove 99.9% of developer and normalise the pH of the emulsion. Even a simple fill and dump water stop would remove at least 95% of the developer.
I do keep a careful eye on the fixer since I re-use it until the fix time reaches four minutes: the maximum fix time recommended by Ilford at double the clearing time as per a visual check. This works out to be far in excess of the normal recommendation for the number films, which seems to have a 100% safety factor built into it.
...and to pre-empt the next question, no I have not had a problem with insufficiently fixed films in the last 27 years, as long as the Ilford guidelines are followed.
Reply
|
|
|
From morningfrost/Silvio (22,728) 
on June 9, 2005 3:56:26 AM CDT
Thank you for the test. As far as I know, it's worth considering the water Ph. If water is alkaline, as it happens in some place, it may take more time to stop development. Someone once told me that the difference is also that stop bath leaves the film in a acid enviroment, while an alkaline one will slow fixer action. If you wish to test more, I often use old fixer as stop bath.
Reply
|
Return to articles
|
