Fuji Acros spec sheet:
"For the stop bath a 1.5 % acetic acid solution is recommended. Immerse the film in the bath at 15 to 25°C (59 to 77°F) for 20 to 30 seconds while agitating."
Fuji Acros spec sheet:
"For the stop bath a 1.5 % acetic acid solution is recommended. Immerse the film in the bath at 15 to 25°C (59 to 77°F) for 20 to 30 seconds while agitating."
I just wanted to get at Ian's BS comment.Kodak says, Ilford says, Fuji says... I figure this will never be settled, so I'll just keep doing what I was doing before. Too many chefs to make this soup any good.
The only flaw here is that stop bath doesn't remove all the residual developer, it doesn't have time to.
Usually the recommend stop bath times are short 10 seconds is one manufacturers suggestion.
So a 1 or 2 minute rinse might actually have a greater effect on removing developer from the emulsion.
In nearly 140 years of Gelatin film emulsions there's never been a theory or evidence that residual developer has lead to any deterioration of a negative, despite the fact that Ilford, Agfa, Kodak and others didn't recommend a stop bath with many films & plates.
In addition they were suggesting a rinse in water after development in highly active developers, with dev times of 2-4 minutes which rather seems to indicate that statements 1 & 3 are rather unlikely scenarios given that most of us develop now in far more dilute modern developers.
Ron's comment about a problem with a 1970 colour paper clearly indicates that carry over with FB papers is a far greater problem due to the dev that's soaked into the paper itself. RC Colour papers came in slightly later.
Food for thought this is what KODAK currently say with film developing
We can assume Kodak know best, which is what Mason (Ilford) & by default Levenson (Kodak) said as well mid 70's
FINAL STEPS
Rinse at 65 to 75°F (18 to 24°C) with agitation in KODAK
Indicator Stop Bath or running water for 30 seconds.
That's up to date Kodak information so lets cut the Bull-shit, that's in the current Tmax data sheet, and in other film data sheets as well.
Ian
Keep in mind that those who recommend stop also sell it. As I said before, I cannot personally recommend one over the other, except as a personal preference, and that I have had no ill effects with water. I do, however, run a pretty tight process. I would say that someone who is sloppy might be better off using an acid stop.
Are you saying my process is sloppy, Jason?
Ian;
Read the whole paragraph. There is a "BUT" in that sentence and he goes on to say something else by the end of the paragraph! And, look at the photo in my last post.
PE
This is a scan of a page from one of the early photo books from Kodak. It describes developing Film, making contact prints and making enlargements.
In it, they describe the best methods to process and wash films and papers.
Take a look at the middle tray and consider the implications in the face of the supposed BS. This shows that Kodak was teaching the use of a stop bath as far back as the 40s. The book is not clearly dated but implies a print date in 1947. I certainly had this book in 1950.
PE
And here is Haist on Stop Baths. He mentions both film and paper. And consequences of not properly stopping development. Please note what he says of a water rinse!
In actual fact, manufacturers recommendations have not changed. They have recommended a stop as did Mason and Haist if you read my posts carefully. They say it is mandatory for paper and recommended for film but you can use a water rinse for film if you must. Then all 3 sources, EK, Haist and Mason list some of the consequences of not using a stop bath.
From your post #108:
"FINAL STEPS
Rinse at 65 to 75°F (18 to 24°C) with agitation in KODAK
Indicator Stop Bath or running water for 30 seconds."
Fuji and Ilford state much the same.
So they all published similar data and Mason and Haist along with Kodak data books agree. A stop is strongly recommended but a rinse can be used with film. A stop is not recommended with paper!
PE
Alan;
Again, you misunderstand. In the diffusion of ions through gelatin, Hydrogen is the fastest and Hydroxide is second in rate, therefore you have an inrush of Hydrogen meeting Hydroxide and a wavefront of neutral water forming as the Hydrogen diffuses downward and Hydroxide moves upwards. When the wavefront reaches the bottom of the coating (or in our tests the undercoat with indicator dye), you stop the reaction. This is virtually instantaneous.
There is a tiny gradient in charge which appears to be taken up by a shift in the equilibrium of the overall medium. Diffusion of Sodium and Acetate for example take place at only a slightly lower rate due to size and this is partly overcome by both shifts in equlibria and in the slight charge imbalance (if any) which takes place. Overall, in the average coating, all diffusion is done in about 15" or less, but the neutralization appears to take place in less than 5".
The two major researchers at Kodak on this were Liang and Tong. They developed a diffusion model for water, hydroxide, acid, dyes and other chemicals through emulsions.
One experiment had the acid anion and proton anchored in place through polymerization of the anionic portion of the acid molecule. They then showed the rapid diffusion of hydroxide into the acid layer to neutralize the alkali. Or, conversely, the proton (hydrogen ion) diffused upwards into the alkaline medium. This led to the development of proper barrier layers in instant products BTW and showed how diffusion and neutralization took place in coatings when acid and base were both present. This "timing layer" was crucial due to the rapid diffusion of either Hydrogen ion or Hydroxide ion. They had to be held back from each other while the development took place and the dyes diffused.
PE
A stop is not recommended with paper!
PE
Yes, it is so, but an approximation. It takes place over less than 15" at 68 deg F.
PE.
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