My chemicals ate air!

[removed account4]

John, I hope that is an air-tight safe!

i keep it outside, just in case!

 

[bsdunek]

In a closed container, there is an equilibrium between the pressure of the gas in the bottle and the vapor pressure of the liquid. The vapor pressure of the liquid can change considerably with changes in ambient temp. Thus causing the plastic bottle to 'cave in' when it is cold and 'bulge' when it is hot.

I think this is the most likely answer. If you, like I, mix your chemicals at the maximum recommended temperature, say 80F, and then seal the bottle and let it cool, it will contract.
Next time, let the solution cool with the cap loose and then tighten it, and I'll bet it won't happen.

 

[Anon Ymous]

I do not believe that 21% of oxygen manages to get into the chemicals. That's just improbable. Barometric pressure changes is much more likely.

Heather, I do believe that developer "consumes" oxygen, let me explain. I keep my print chemical solutions in plastic fizzy drink bottles. At the end of the printing session, everything gets back to the bottle. Everything is stored at the same place, resulting in same pressure(s). One day later, the developer bottle has shrunk, not the other two. IIRC, stop bath doesn't oxidise, it's acetic acid with a tiny amount of indicator. Fixer has ingredients that can oxidise (sodium sulfite does), but it's bottle volume remains the same. It seems it's the developing agents that have the tendency to react more rapidly with oxygen.

FWIW, using lighter gas (propane - butane mix) seems to prevent this. Of course, initially the lighter mix has low temperature, so pressure inside will increase significantly. I tried loosening the cap, thus equalising the pressure inside and outside the bottle (you can hear the gas escape). If I let it for a day or two (or more) the bottle's volume doesn't change.

 

[dancqu]

Although Dancqu loves single shot fixers,
I prefer using two-bath fixing.

I'll expand on that:
"... fresh each session, very dilute, single shot fixers,
using minimal solution volumes, ..."

Such fixers can have good chemical milage and 'archival'
levels of dissolved silver from one fix, with no testing
needed. A space saver. Integrates nicely with single
tray processing. Films and papers wash fast with
less water.

If my volume of prints and films warrented AND
space were abundant I'd go two-bath. Dan

 

[Vaughn]

Sorry, Heather, but science is going against you with this one....and also against what I observe regularly (running a teaching darkroom, we have many bottles of developers, stop, fixers, etc.). This always happens to partially filled tightly sealed plastic bottles of developers -- and as anon notes -- never to bottles contain non-oxidizing chemicals. And if the bottle is glass, one hears the intake of air as it gets sucked into the bottle as one unscews the cap.

I do not believe that 21% of oxygen manages to get into the chemicals.

It is not 21% of the oxygen, but almost 100% of it -- which comprises of 21% of the normal air around us.

If a chemical reacts with oxygen, it will react with it until there is no more oxygen it can react to (or until the chemical is completely oxidized). This is the reason the shelf life of a developer in a half-filled bottle is only a third of that of a full bottle (both tightly sealed). And why a tray of Dektol, even if not used, will die within 24 hours...all that surface area and an unlimited amount of oxygen to react with.

The problem is made worse every time one opens up the bottle to use a little of the developer -- the partial vacuum created by the removal of the oxygen from the air above the liquid, sucks fresh air into the bottle, providing even more oxygen for the developer to react with and killing the developer faster and faster.

ic-racer. What you say is partly true. But there is not an equilibrium in a freshly sealed half-filled bottle of developer. Chemical reactions are taking place...oxygen gas is being "consumed" (changed from O2 to new chemicals with oxygen atoms freshly attached to them) by the chemicals of the developer. Once all the available oxygen gas is "consumed' and removed from the air space above the liquid, an sort of equilibrium is reached, if that would is the proper word for an unstable chemical (developer). From that point, changes in temperature will affect the vapor pressure inside the bottle -- but it is insignificant compared to the reduction of the pressure inside the bottle due to the removal of oxygen gas.

And there is some reduction in pressure inside of a sealed bottle of a hot liquid once it cools down -- enough to suck in the sides of a plastic bottle if there was some air space in the bottle. But that is not what is happening to a partially filled bottle of developer. Chances are that the liquid was room temp when the cap was put on, after all, it is partially empty because one has been using it over an amount of time...time enough to cool down.

I remember my 7th grade science teacher having a gallon gasoline can on a bunston burner on his desk -- after the little bit of water inside of it boiled, he took it off the flame and screwed on the cap, and went on with the class. As the can cooled, the sides started to cave in dramatically and with much noise. An impressive experiment -- got our attention!

Vaughn

 

[Jordan]

By the way, I walked into a walk-in refridgerator at work a couple Mondays ago that someone had put several pounds of dry ice into on the previous Friday. The the room was full of "air" but it had about 17% oxygen instead of the 21% my body was expecting. I noticed the taste of the air was odd, and about a minute later, I was feeling a little tight in the chest. I found what I was looking for and left the room, and felt like I was going to pass out about 30 second later. Pretty odd sensation. Good think there was still some oxygen left... At least I now know what being at the top of Everest is like now!

Sounds like a really dangerous situation. The labs I've worked in have always kept dry-ice in its own ice-chest in a well-ventilated area, or even outside.

Your symptoms were likely only partly due to oxygen deprivation -- I am more inclined to blame mild CO2 poisoning. Suffocation by CO2 can happen even in the presence of lots of oxygen (acidification of the blood, etc.)

Dry-ice is definitely a substance to be respected -- I always try to remind my self that 44 g of the stuff "wants to be" 22-odd litres of suffocating gas. (PV=nRT and all that)

 

[tkamiya]

Thank you, Bozwart!

A good way to do that is to see if it will clear a small clipping of film. The leader that is cut off the 35mm roll when loading the tank is perfect for this; doesn't matter if it has been exposed. The test? Does it clear, or doesn't it?

I wanted to thank you for this tip. Since I went shooting today I had all of my chemicals out and I had a chance to try it. A small clip from film was submerged into the fixer and it cleared in few minutes. I am assuming by "clear" I am supposed to check if all of the emulsion materials gone and all that is left is the base film material. It was.

 

[Kirk Keyes]

Sounds like a really dangerous situation. The labs I've worked in have always kept dry-ice in its own ice-chest in a well-ventilated area, or even outside.

Your symptoms were likely only partly due to oxygen deprivation -- I am more inclined to blame mild CO2 poisoning. Suffocation by CO2 can happen even in the presence of lots of oxygen (acidification of the blood, etc.)

Dry-ice is definitely a substance to be respected -- I always try to remind my self that 44 g of the stuff "wants to be" 22-odd litres of suffocating gas. (PV=nRT and all that)

Yeah, it sure was a dangerous situation, looking back on it. They did put oxygen sensors in the walkins and one ready 21% and the one I went into read 17%. So now there are alarms for low oxygen content. And we trained the field people that use the dry ice to chill samples in coolers about removing the dry ice before putting their coolers in to the walkins. My understanding was there was about 5 lbs of dry ice that was put in there. So it certainly was a combination of low oxygen and high CO2 concentration.

 

[Larry Bullis]

I wanted to thank you for this tip. Since I went shooting today I had all of my chemicals out and I had a chance to try it. A small clip from film was submerged into the fixer and it cleared in few minutes. I am assuming by "clear" I am supposed to check if all of the emulsion materials gone and all that is left is the base film material. It was.

This is often a very useful "dumb test". Another one is the "Is this developer?" test. Put some exposed film, a clip as in the other one is good. Does it turn black? It doesn't tell you much about the specific qualities of the chemical, but at least you have a starting point.

I once had an assistant who somehow got the idea that fixer should be mixed from concentrate in the same proportion that photo flow 200 is mixed. 1 part to 200 parts water. The fixer test showed that there was a very slight clearing over a rather long period of immersion. Replacing the fixer several times, over a longer period of time, eventually showed what might be happening; at least I knew what questions to ask. She was from Moldova and couldn't speak much English, and I could speak less of her language.

We got it straightened out, but not before some real disasters occurred. The oft-practiced dumping of mystery chemical problems down the drain wouldn't have worked in that situation. My suspicion was that the same thing would only keep happening. Students were losing their work right at the end of the term.

Glad you found it useful!

 

[dancqu]

Fixer Testing

A good way to do that is to see if it will clear a small
clipping of film. The leader that is cut off the 35mm roll
when loading the tank is perfect for this; doesn't matter
if it has been exposed. ... Does it clear, or doesn't it?

If the portion of film being tested has been exposed
the silver with in the emulsion may have printed out.
That is the silver has become elemental due to it's
reduction by exposure to light. IIRC I've a few
black leaders packed away.

It is important to note the time needed to clear using
a FRESH fix. Twice that time is the standard minimum
fix time for a FRESH fix. With USED fixer if the time to
clear exceeds twice the fresh fix time to clear then the
fix should be replaced with fresh. The time to fix in all
cases is twice the time to clear.

Of course if you use your fixer one-shot, as I do,
then testing the fixer as it ages for it's clear
time is not needed. Dan

 

[ic-racer]

A little hypercapnea and hypoxia and you could make the scientific journals:
http://linkinghub.elsevier.com/retrieve/pii/S0735675705001075

 

[ricksplace]

Mix your chems in the large bottles you currently have, then decant the chems into smaller bottles like empty plastic water bottles. Fill them all the way to the top (no air space). Filled like this and stored in a cool place, your chems should last for up to a year. Make sure you label the bottles well. Wouldn't want anybody drinking the stuff.