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Gentle stop bath


chris_raney

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I need wiser heads to tell me about alternative stop baths for film.

I'm using scratch-made divided D-76 and off-the-shelf Kodak F-5

fixer. I know there are lots of complaints to the use of the latter,

but it works, I'm in no hurry and I always use hypo-clear before a

wash.

 

My concern is about my acetic acid stop bath. I now realize that

those funny little holes in my sheet film from years back weren't due

to poor production standards at the film manufacturer, but from my

own ineptitude with the chemicals. I suppose I was too heavy-handed

with the acetic acid in the stop bath.

 

Since I live in a hot climate, Iメve been adding sodium sulfate to my

developers and stop baths to prevent excessive swelling (but not in

the divided D-76 formula, of course). But as of late Iメve become a

thorough reader of Anchellメs books, and it appears as though the

acetic acid should go.

 

Anchell makes an anecdotal reference (an infuriating habit of his,

when really important information should be spelled out) to using 10

grams of sodium bisulfite per liter of water as a gentle stop bath.

Since Iメve been using the borax developer I know the instance of

pinhole producing carbon dioxide bubbles is less likely than with

other developers, but I would like to eliminate the danger entirely.

 

Iメm sticking with the Kodak fixer until I burn up all the packages.

But does anyone out there have any experience using sodium bisulfite,

or any other alternative to acetic acid?

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Dilute sodium bisulphite (or metabisulphite, practically the same thing) is fine. It's acidic so is reasonably effective at stopping development, and is very compatible with developers, not producing any reactions or bubbles. It smells like acidic fixer (SO2), but very dilute it won't irritate you too much. It can be used quite dilute. I used it for a while, but eventually started to use just running water.

 

There is an alternative acetic acid fixer that is buffered to a less acidic pH than just acetic acid. It is considered by some to be less aggressive to the emulsion. The following was cut from a posting from Ryuji Suzuki at (I think) apug.org. The second method of mixing is probably more convenient, since lye is easier to buy than sodium acetate.

 

<start of quote>

 

buffered stop bath (replenishable)

 

Written by Ryuji Posted: 06:09 AM - 01-19-2005

 

acetic acid, 90% 20ml

 

sodium acetate 80g

 

water to make 1.0 liter

 

target pH 5.0 plus/minus 0.5

 

same thing can be made this way:

 

acetic acid, 90% 60ml

 

sodium hydroxide 25g

 

water to make 1.0 liter

 

target pH 5.0 p/m 0.5

 

Either bath can be replenished at the rate of 30 ml glacial acetic acid per each 30 of 80 sqi processed. Buffered stop bath may appear more expensive but lasts MUCH longer than 1.7% acetic acid bath. The replenishing capability is very useful for Nova slot processor because changing the entire bath is a real pain in that processor.

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I agree with Ivan and always use water (with only two changes).However,if you MUST use an acid stop bath, I've been using citric acid for FB prints, mainly because it doesn't smell like acetic acid. I wonder if this would be more gentle for film?

 

Kodak SB-7 Citric Acid Stop Bath

 

Water 750.0 ml

Citric acid (monohydrate) 15.0 g

Water to 1.0 l

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I second Ivan's recommendation for plain old unadorned H20. Might need to decrease

development time a tiny bit, but it's the gentlest way to go.

 

Follow that up with an alkaline fixer such as the Formulary's TF-4, and you'll have an all-

alkaline, nonacidic development process that won't require hypo clear and washes archivally

clean in 5 minutes.

 

Simpler, better.

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Dilute citric acid can also be used as a stop. I've made stops at pH values up to 5 that work well.

 

Please remember though that todays films do not suffer any damage when going from developer to stop. This does not happen with modern hardeners and has not since the 60s.

 

Even back then, the pinhole problem mentioned here was not due to a stop. It was due to air bubbles being entrapped on the surface of the film for the most part.

 

Any effect caused by a stop bath with a carbonate developer came in the form of blisters or 'fish scales' on the surface of the film or print. I have done the experiments personally both at Kodak and here at home with hand coatings to prove and re-prove this! Stop baths don't cause pinholes.

 

You may get blisters and defects on films that are extremely soft. This includes some films made by non-mainstream manufacturers. There are threads here that report on this.

 

Ron Mowrey

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I am thankful for your response, Mr. Mowrey. It is wonderful for me to rub shouldersラas it wereラwith one of experts of photographic chemistry. But it is sad that chemical photography is rapidly disappearing, and that expertise like your is wasted on most of the youthful photographers of today. Though I'm fairly new to photography, I'm no longer a youth! I'm a boomer with a love of the old ways, and I'm thrilled to have stumbled across this website a few months ago. The level of talent and expertise I find here is enormous. But of course, there are a few idiots and stumblers as well. I consider myself in the latter group.

 

Again, thank you for your response, and I'll read your archived comments with relish.

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Hi Chris,

 

My question is why in heaven's name would anyone want a "gentle stop bath"?

 

Normally we work with 2% to 6% acetic acid however I did research on this with everyting from water, to 1%, to various percentages up to 50%. From 2% on,there was no difference. Jest because it stings the cuts on your hand, that doesn't mean that it is harmful to the film.

 

Acetic acid stop bath (short stop) not only stops development immediately, it prevent oxidation stains with water, furthermore, hypo toughens the emulsion without hardening it, and it also prevents the degradation of the the fixer (hypo). Carrying over alkaline developer (even in tiny quantities)causes colloidal sulfur which can't be seen until huge quantities are found and visible. Colloidal sulfur will be in your emulsion and isn't removed (even by hypo clearing agent). Over a period of time whether in film or prints will sulfurize and oxide. This will stain brown and then will disappear.

 

Lynn

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