Kodak Indicator Stop Bath failure?
A couple of days ago I mixed up 5 liters of Kodak Indicator Stop Bath (I have 5 liter bottles). Today I went to use some, and when I poured it out it was clear! I was surprised to see this, and it also didn't smell like stop bath, but rather sort of like the smell of a box of bandaids. I tested the pH of the stop bath, and it was still acidic (I used a swimming pool tester, so I don't know the exact pH), I then tried pouring some developer into it to see if it would turn purple, and it didn't. Is it possible that the indicator has gone bad? I've never seen this before!
I mixed up this stop bath with tap water rather than distilled water as I was running low, and figured it didn't matter to stop bath, my local water is slightly alkaline, but the stop bath was the proper color yellow when I first mixed it.
Can anyone tell me what's going on?
I've never heard of such. It is almost impossible for acidic acid to "go bad" as it is already as bad as it can get (the final stage in oxidation of ethyl alcohol)
The indicator is a stable dye so I think that is not a possibility either. Acidic acid in stop is so concentrated nothing I can think of in your tap water could possibly overcome it. That leaves only one possibility in my thoughts: maybe you had the wrong bottle. I sometimes think my developer(s) solutions smell vaguely like "band-aids".
I love the smell of fixer in the morning. It smells like...creativity!
Truly, dr bob.
I would like to second the "wrong bottle" possiblility. On one occasion I used Dektol instead of stop bath when developing a roll of film (I had clearly marked the bottle, I have no excuse<g>). There are lots of similar stories wandering around the various photography forums.
I will keep my even more embarrassing gaffs to myself. ;>)
A second "second".
Originally Posted by Neal
Mix up some new stop bath. Poor a little of the bad stop into it. 50 cents says it turns purple.
[QUOTE=dr bob]It is almost impossible for acidic acid to "go bad" as it is already as bad as it can get [QUOTE]
My thoughts exactly
My photos are always without all that distracting color ...
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Originally Posted by David Brown
Well, 50 cents would be wrong! This is not a case of wrong bottle, or wrong chemical in bottle. Stop Bath is one of the few Kodak chemicals left that I still use, and it's odor is very distinctive, I don't think I would mistake it anywhere. But, as you suggested, I mixed up some new stop after pouring most of the old down the drain (I saved some to try adding the new stuff to) Mixed up the new stuff, and it too was nice and yellow like it's supposed to be (and like the original batch was originally), added some of it to the old stuff, and it just turned slightly yellow.
I'm not saying I'm above mixing up the wrong chemicals, I've done it a couple of times in the past (I found out that when you use fix first the film comes out extremely underexposed ) but Stop Bath is not one of the chemicals I would confuse.
It's going to be interesting to see if this batch also turns clear within a couple of days!
Sorry. I owe you 50 cents.
Originally Posted by MikeS
Can't imagine what happened. Fortunately, stop bath is cheap!
It's doing it again!!
well, now it's getting weird. I mixed up a second batch of stop bath, and within a few minutes it's already starting to turn clear! A friend here suggested that perhaps because I'm using a water storage type bottle (I got it a Walmart, it's got a spout on the bottom, and they stack real nice next to each other) that perhaps it's not acid resistant, and after using it for more than a year to hold stop bath perhaps the rubber seal is breaking down and effecting the stop bath. I've just mixed up a liter of stop bath in a separate container, and I'm waiting to see if it too turns clear. If so, then it's got me really nervous about what chemicals are in my local water
Not sure what indicator Kodak uses but I've found the Ilford odourless stopbath does lose some of the yellow colour before it changes to purple. I tend to toss it when it gets to this stage. One thing you can try is a poor persons titration to find out if the potentially contaminated stop has had its pH changed. Basically you pour a fixed amount of fresh stop mixed in a glass container into a beaker (or some other glass container) and add an alkaline solution (you can use developer or a sodium bicarbonate solution) noting how much is required before the indicator changes colour. Make sure you swish the solution around to ensure it's properly mixed. Then do the same thing for the possibly contaminated stop using the exact same alkaline solution and the same amount of stop as in your first test. This should tell you if your contaminated stop is less acidic than a fresh solution. If you were pedantic and had access to a chemical lab you could take it further but it'd be easier to distill/filter the water and buy a different storage container.
i have been following this with some interest and can't really add to those above, but i just can't help asking; why pre-mix the stop bath?