Storage Life of Developers

[Raghu Kuvempunagar]

An interesting study: https://healthprofessions.udmercy.edu/academics/na/agm/phenvitc.htm

 

[Alan Johnson]

An old study that missed the key factor, the amount of air allowed into the bottles.
Under "Storage" it merely states that the containers were "partially filled".

 

[Raghu Kuvempunagar]

An old study that missed the key factor, the amount of air allowed into the bottles.
Under "Storage" it merely states that the containers were "partially filled".

That's right but partially filled is how most users store developers in containers.

 

[relistan]

I think the most interesting thing in here, to me, is that the difficulty of measuring phenidone amounts made the attempt to track preservation from powder almost impossible to do properly with the decent equipment used in the experiment. This may be one of the reasons people have such mixed results with stored phenidone. I have found personally that many years old phenidone works just fine in my recipes.

 

[Alan Johnson]

That's right but partially filled is how most users store developers in containers.

They seem to be presenting it as a scientific comparative experiment but it is not, unless "partially filled" is the same in all cases, which is not stated.

 

[Raghu Kuvempunagar]

They seem to be presenting it as a scientific comparative experiment but it is not, unless "partially filled" is the same in all cases, which is not stated.

Identical bottles, identical storage conditions, and identical amounts used at each stage. So I would think that the "partially filled" is nearly same in all the cases. [Edit: My assumption was not correct. Please see my later post for more info.]

 

[Alan Johnson]

Partially filled can mean as much as 100 to 1 variation in the volume of air to the volume of developer and partially filled is specifically listed under Storage. There is no claim that partially filled was always the same. So there is an experiment in which one variable, a very important one, was either not controlled or not explained clearly in the write up.

 

[Don_ih]

Given the different developers were used at different dilutions for various tests, then these partially filled bottles would soon all have differing amounts of remaining developer - so more air in some bottles than others. That does amount to a fair comparison between developers as used in a regular situation but is a bit away from the control you would want for scientific conclusions.

 

[Raghu Kuvempunagar]

Good point. I just now sent mail to the author of the study requesting him to clarify on "partially filled".

 

[markbau]

Does anyone else exhale into a partially filled bottle of developer to decrease the amount of oxygen left in the bottle? An ancient old lab worker told me about it and I’ve always done it. No idea if it does any good!

 

[Raghu Kuvempunagar]

Good point. I just now sent mail to the author of the study requesting him to clarify on "partially filled".

He responded: "No, I did not control for fill level in the bottles, nor did I displace the air above the liquid with nitrogen (sometimes done to slow oxidation)."

 

[Don_ih]

He responded: "No, I did not control for fill level in the bottles, nor did I displace the air above the liquid with nitrogen (sometimes done to slow oxidation)."

It replicates actual darkroom conditions, so I think it's good enough for drawing practical conclusions. Frankly, practical conclusions are the only ones that matter.

 

[runswithsizzers]

Does anyone else exhale into a partially filled bottle of developer to decrease the amount of oxygen left in the bottle? An ancient old lab worker told me about it and I’ve always done it. No idea if it does any good!

A quick search indicates that exhaled breath has about 15-16% oxygen compared to the atmosphere which has about 20-21% oxygen. That is about a 24-25% reduction on oxygen. Might help, but I suspect other gasses with little or no oxygen should be more effective.

 

[Alan Johnson]

It's a very old experiment with both the formulae PC and PX involving replacement of sodium ascorbate by ascorbic acid. I think it was well known about 15 years ago that this resulted in a big drop in activity, way below any formula actually in use today.

 

[Sirius Glass]

So again XTOL is a better developer, as expected from Kodak.