Stupid Kodak Indicator Stop Bath Question

logan2z

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I've always used Ilford's Ilfostop stop bath but recently decided to switch to Kodak Indicator stop bath and I'm about to use it for the first time. The instructions on the bottle say to mix 16ml of stop bath and 984ml of water to make 1 liter of working strength stop bath. The online Kodak directions say to mix the stop bath in a 1:63 dilution. Something doesn't add up - 16ml:984ml is not 1:63, it's 1:61.5. Maybe Kodak just decided to round up to make it simpler (then why not 1:62? ). I'm sure the exact dilution isn't super critical for stop bath but was just curious about the discrepancy.

Also, I use a 500ml Jobo 1520 tank for film developing. I assume it's perfectly fine to simply halve the quantities of stop bath and water to maintain the same dilution but mix 500ml of working solution instead of 1 liter. Not sure why Kodak doesn't just list the dilution instead of the amount of working strength, like Ilford does. Presumably there's enough stop bath in 500ml of working strength to adequately stop development in the 30 secs recommended by Kodak.
 

MattKing

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Historically, Kodak dilution instructions used 1:63 the same way as Ilford used 1 + 63.
But outside of that, Kodak could have specified 15.625 ml + 984.75 ml for the exact ratio, but that might not have been particularly helpful.
For indicator stop bath, the exact concentration isn't particularly critical.
And yes, it isn't really the volume that matters for the sort of developing we do, it is the concentration.
If you were mixing up stop bath for a large commercial dip and dunk machine, you might very well be using the old 16 oz bottles to make up the 8 US gallons of working strength stop bath - that is where the ratios came from originally.
FWIW, if I'm not developing multiple rolls of film, I mix it up half strength, and discard it after using (and possibly re-using) it for a day's session. It works fine that way, and doesn't smell quite as bad.
 
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logan2z

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Thanks Matt. I'll just mix it using 8ml of concentrate and 492ml of water and use it over multiple sessions until the indicator kicks in.
 

Nicholas Lindan

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1:63 is 1/2 oz to make 1 qt of working solution. Or, if you prefer (cough) use 2 drams to make a pint.

If you insist on liters then it would be 4 5/16 drams to a liter. Better to use quarts....
 

warden

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logan2z said:
I'm sure the exact dilution isn't super critical for stop bath but was just curious about the discrepancy.
Click to expand...

I think you’re right and to be honest after accurately measuring for a while I just wing it nowadays and judge by color. If it’s yellow I’m mellow.
 

MattKing

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logan2z said:
Thanks Matt. I'll just mix it using 8ml of concentrate and 492ml of water and use it over multiple sessions until the indicator kicks in.
Click to expand...

That is probably okay with the acetic acid based Kodak stuff - although you should discard it when it looks distinctly less yellow - don't wait until you see blue/magenta.
It isn't a good idea with the citric acid based stuff like Ilfostop - nasties can start growing in it.
 

RalphLambrecht

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For indicator stop bath, the exact concentration isn't particularly critical.
 

Bill Burk

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Nicholas Lindan said:
1:63 is 1/2 oz to make 1 qt of working solution. Or, if you prefer (cough) use 2 drams to make a pint.

If you insist on liters then it would be 4 5/16 drams to a liter. Better to use quarts....
Click to expand...

Half ounce to make a quart! Thanks.

I have a strange glass tube with ten marks to a quarter ounce.

And I always use four of those marks to a quart.

That is 1/10 ounce to 32 ounces.

I probably will forget this tomorrow, but four marks is what I settled on.
 

koraks

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logan2z said:
I'm sure the exact dilution isn't super critical for stop bath
Click to expand...

Exactly. I'd go with "a dash to a jar of water" and call it good.


logan2z said:
Presumably there's enough stop bath in 500ml of working strength to adequately stop development in the 30 secs
Click to expand...

Absolutely.

So don't sweat it. 1+63, 1+61.5, 1+70, 1+50 - it really doesn't matter. No fuss.
 

pentaxuser

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Patrick Robert James said:
There really isn’t much of a reason to use stop bath with film.
Click to expand...

My understanding is that any difference between water stop and acid stop in the processed negative depends largely on the length of the development time For very short times such as round about 5 mins then acid stop might make a measurable difference or might even make a difference that you can see in the processed print but if a video on such a test exists Í haven't heard of it or seen it

I can't say that over my kind of times of 10-12 mins development times I saw any difference when I switched to a water stop involving about 3 dumps of water

pentaxuser
 

laser

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The dilution of stop bath isn't very critical. One glug is about right.

Stopbath lowers the pH and stops development quickly so if you are doing precise development it will help. It also increases the capacity of your fixer. That said the only time I regularly used stop bath was when making technical images that required density matching +/- .01. Timing was within 1 second.
 

laser

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After I posted I realized I also used stop bath to increase the capacity of fixer in replenished high volume film and paper processors including the Royalprint Processor Model 417. 4= activator+stop+fix+wash, 17 = 17 inches wide. A great workhorse paper processor for Incorporated Developer (ID) Papers. Interestingly X-Omat (x-ray film) Processors did not use a stop. This was a trade off of processing time (dry-to-dry) of 90 seconds (1980) for fix capacity. It was better to spend the time in fixer than stop bath.
 

Bill Burk

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Additional comment. When I mix a tenth of an ounce to 32 ounces, I get pH 4.1

It only takes a couple prints dragging through until it turns from orange to purple. You can see it in the tray by light of safelight.

So basically “indicator water”. If you were to use 32 ounces of water in a tray as a stop bath, replace the water frequently. Two or three prints.
 
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