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  #1  
Old 3rd January 2010, 07:06 AM
jbleffert jbleffert is offline
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Default exhausted indicator stop bath

I'm a bit confused on how to know when Kodak Indicator Stop Bath is exhausted. I've mixed up a liter or so and have used it to process about 20 rolls of film at standard dilutions. The bottle says it changes color under safelight or under normal light, but I've read elsewhere that the color change is only visible under safelight.

The color of the stop bath hasn't changed (at least from what I can tell), but I don't have a safelight as I only do film processing, not printing.

Is it obvious when the stop bath is exhausted?

Thanks!

-jbl
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Old 3rd January 2010, 07:09 AM
Dave miller Dave miller is offline
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Welcome to the forum jbl.
I have never used the Kodak product, but assuming it is similar to other indicating stop bath products, it will change from yellow to purple when exhausted.
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Old 3rd January 2010, 08:53 AM
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As Dave says it goes very purple when exhausted and looks much darker under the safelight.

BTW: Welcome to fadu.
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Old 3rd January 2010, 09:59 AM
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jbl welcome to FADU and I hope to see some images from you sometime.

The colour of your stop bath will change quite dramatically when it is nears exhaustion (as stated by Dave and Bob). I would expect to see this change under normal lighting conditions and that's the way I have used stop baths in the past. However, I no longer use them for B&W films and prefer to user a plain water rinse (at the developer temp) which is thrown away after use.

Neil.
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Old 3rd January 2010, 11:15 AM
marty marty is offline
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Hi and welcome aboard, jbl. Kodak Max Stop changes from intense yellow (freshly mixed) to a pale blue/greenish when near exhaustion. This viewing under normal light, under red safelight it looks very dark when near exhaustion. That said I feel safe to clarify that I use it only for papers, since I prefer a plain water rinse for films.

Cheers, Marty.
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Old 3rd January 2010, 07:22 PM
jbleffert jbleffert is offline
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Thanks, everyone! And thanks for the warm welcomes!

It sounds like my stop bath is still fine, I'll keep an eye out for a color change.

I've just started getting into both B&W and home processing, but you can see some of my recent work at

http://jbl.smugmug.com/Photography/LearningBW

Best,

-jbl
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Old 3rd January 2010, 08:05 PM
Mike O'Pray Mike O'Pray is offline
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Hi jbl and welcome. As others have said you should see a distinct purple colour when pouring it into a dev tank. Stop can be kept in a clear container so the colour will show before you attempt to pour into the tank.

Some makes of stop bath are sold so cheaply and used at such small dilutions that a use once and dump method would still be cheap.

Just be a bit careful if you move to a Nova Quad four slot print processor. Take the tube from the slot in good light.

I tend to switch to safelight then remove the tubes and with the Nova being in a shady area of the darkroom and the slots being only about an inch wide I confess to having used exhausted stop on at least one occasion without recognising it as being exhausted.

Again the cost means that draining the slot and re-filling with fresh fairly frequently shoud be the order of the day but laziness or a desire to start printing can get in the way in my case.


Mike
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Old 4th January 2010, 12:02 AM
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If you want to see what it looks like, put a little diluted stop - say 20-50ml - in a beaker and slowly pour unwanted/exhausted/used developer in - once the pH approaches 7 (neutral pH) it will change colour.

It is best to change it as soon as it changes colour as it is then essentially water as far as its stopping qualities are concerned - but no need to panic if you miss the colour change - acid fixer is generally well buffered against carry-over of the alkaline developer so a few prints/films will not make a significant difference to the life of the fixer.
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Old 4th January 2010, 07:58 PM
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Martin Aislabie Martin Aislabie is offline
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I use the same Kodak Stop Bath

The colour will change under Safelight or Room light.

The deep clean yellow of new Stop Bath starts to look darker and muddier as exhaustion approaches before eventually going purple.

As Stop Bath is cheap as chips, I make mine up at half the recommended strength and then chuck it at the end of each session rather than bothering to keep it

As long as the Stop stays yellow its doing its job of arresting the action of the Developer

Martin
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