How to know when stop bath is exhausted if you don't have a safe light

I'm working with Kodak Professional Indicator Stop Bath for the first time, and the included instructions state that the indicator will change appearance under a safe light.

I don't have a safe light. Will the appearance also change under normal light, or is there some other way to tell when it's spent?

Use water instead. Never have to worry.

Indicator stop bath contains an indicator dye which is yellow when the bath is good but turns purple when its pH is too high for it to work. This is what you would see with normal room light. With an amber safelight the bath appears colorless when good but appears to turn black when bad.

I personally consider an acetic acid ISB a waste of money and the addition of one more chemical to the environment. Acetic acid has its own indicator in that you can get the same information from the bath's smell. Little or no smell time to change to fresh. However I only use a stop bath for FB base paper. A couple of rinses wok well for RC papers and films.

White vinegar works well, is cheap, and is available just about anywhere. Check the label as some brands are 4% acid while others are 5%. To get a 3% stop bath from the latter use 3 parts vinegar and two parts water.

Turn on the light. If it is purple it has gone bad. Just like Jerry said.

Thanks all. If I had known that it's just concentrated acetic acid I wouldn't have bought it.

It cost for the indicator makes it worth it. I have used it since 1960.

T . said:

Thanks all. If I had known that it's just concentrated acetic acid I wouldn't have bought it.

Click to expand...

some folks use citric acid its cheap and ez to use.

i use hydric acid ( DHMO ) i get it locally,
i don't pay much for it, and it works OK.
i dont't worry about the indicator. i get rid of
the DHMO every few runs, nomatter if i am
processing film or souping prints. i get it in bulk.

I use Citric Acid from the health food store. Cost is about $6 a pound. A couple tablespoons in an 8x10 tray is all you need. After a few hours I'll add another tablespoon full just to err on the safe side.

Not sure why anyone would pay to ship stop bath these days, unless you do color.....

You can tell by feel. Dip your index finger and thumb into the developed, rub them together. They will feel slippery. Now dip them into the stop bath. They should immediately stop being slippery when rubbed together. If your fingers are still slippery, the stop bath is exhausted.

I also use a few teaspoons of citric acid crystals from the drugstore for my FB work. Cheap, easy and without any issues.

Lars

The Kodak Indicator Stop is a good product. A bottle will last a long time and the assurance of having the indicator to confirm your suspicions that the stop has truly gone bad. Don't feel bad for buying it.

Don't wait till the stop has turned really blue; toss it at the first sign of color change (it looks less yellow with a little grey). Having a white tray for the stop helps with evaluation.

Kodak Indicator Stop working solution will keep for a long time. Reuse it till it is ready to toss to get the most economy out of it. Keep separate bottles for film and prints though.

Best,

Doremus

Rick A said:

You can tell by feel. Dip your index finger and thumb into the developed, rub them together. They will feel slippery. Now dip them into the stop bath. They should immediately stop being slippery when rubbed together. If your fingers are still slippery, the stop bath is exhausted.

Click to expand...

Makes perfect sense, hadn't thought of it before. Thanks for posting this tip.

I see it as false economy to try to work stop bath to death. The negative effects of exhausted stop bath come into play earlier than the time the stuff changes color and turns to, well, sludge (polite term) in your tray.

For decades I ran an enormous amount of film thru my darkroom, and carefully monitored all my chemistry. Processing brews were never allowed to get to the point of even near-exhaustion, but were turfed on a regular timed basis. Usually bi-monthly or, when my darkroom was doing a lot of work, every week.

Consequently in my 50+ years in the darkroom,I have never had indicator stop bath change colors on me.

Now I do much less processing, but I still adhere to a fixed schedule for disposing of my chemistry. End of the month, it all goes out, used or not. More often if well used. Easy as sucking chips, and a virtual guarantee of no disasters to my negatives or prints down the track.

Citric acid in a water bath works just as well (in fact I've had this verified by a photo chemist). If I had to, I would also use plain water from the tap with a dash of household vinegar, or just water, boiled and allowed to cool.

Trying to squeeze the last little bit of use out of one's darkroom chemistry is, I think, akin to running the car on a virtually empty petrol tank for a few more miles because the gas station just over the next hill has the stuff on sale at two cents cheaper. Eventually it all catches up on you.