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Rodinal is well known for staying the same with age!
In rordinal type developers the developing agent p-aminophenol is present as a phenolate formed from sodium or potassium hydroxide. Such a phenolate can absorb carbon dioxide which reduces the developers activity. The phenolate is converted back to the developing agent and sodium or potassium carbonate. Both compounds are insoluble in the developer and crystalize out. There is also a reduction in the alkalinity of the concentrate. For samples with a lot of precipitate, if you cannot get it to redissolve by shaking and heat it really should be discarded.
It may be that air in the large container causes oxidation of sulphite to sulphate, which lowers the pH. Some p-aminophenol may then crystallise out.Doesn't this kind of contradictory but my experience has been?
One of the things that happened was that like someone mentioned above, I transfer my Rodinal from the original plastic bottle to glass bottles. I have one larger storage bottle, and then a mini smaller bottle that goes with the rest of my kit that has a dropper. So periodically I refill the smaller bottle from the larger one.
About two months ago, I went to refill from the larger bottle and noticed that the plastic cap on the larger bottle had cracked and that the developer inside had gone very much more crystallized than I had ever seen it. But when looking at the negatives I didn't notice any issues, the exposure was correct, and the image seemed very sharp, it didn't seem sharper than before, but I was more concerned about it looking unsharp and so I wasn't really thinking about it. It was only with this new bottle that I went to look and noticed that it seemed as if the older contaminated with oxygen bottle of Rodinal seem to produce sharper images. Does this mean if I leave the container open for a couple days and sort of allow that process to happen, that I might be able to cause the effect of the "aged" Rodinal?
You said to throw it out, but in fact I was able to use it and get seemingly better results...
It may be that air in the large container causes oxidation of sulphite to sulphate, which lowers the pH. Some p-aminophenol may then crystallise out.
From 1910, "small quantities of white salt are deposited....formed by the action of the air on the sulphite used.."
But "In no way is the energy of the developer affected thereby"
See p26-7:
http://www.archive.org/stream/agfabookofphotog00barrrich/agfabookofphotog00barrrich_djvu.txt
You said to throw it out, but in fact I was able to use it and get seemingly better results...
As the developer absorbs oxygen and carbon dioxide from the air its activity is reduced. This change is small enough in most cases to cause any visible change in the negatives. For severe cases developing times may need to be extended a bit. My main point was that activity will not increase with age but rather decrease.
So then how do you explain the difference in Acutance?
Once you add a scanner to the process you add another variable. Do you see any difference in actual silver prints from the two sets of negatives? Even so any perception of grain or acutance differences is highly subjective.
Fairly easy to explain. You have no way of objectively evaluating acutance, nor have you conducted controlled, side by side tests. So you don't know there is a difference in acutance.
if you had been using a bottle of Rodinal from 1995 and just bought NOS Agfa Rodinal 2005 or R09 then they are not the same exactly.
I've used a 1/4 full bottle that was 25 years old until last drop and solid particle and not noticed a different with next bottle.
We need a real organic chemist cause I thought Rodinal kept well cause of an excess of preservative and if you filtered it and rebottled it would not last long?
But maybe I'm using the wrong word, but when the edges of the dots are fuzzy instead of looking sharp, I assume that Acutance is the level at which the edges of the dots appear sharp.
Is the grain affected the same way as the subject?
I'm not sure exactly what you mean by that? The role that I have lots of comparison shots for Acros100 was shot in studio with strobes, so there is no motion blur if that's what you mean?
Grain cannot be evaluated from a positive image because what is mistaken for grain is actually the space between the grains. Remember everything is reversed in a positive image. Grain can only be evaluated by looking a the actual negatives with a microscope. This is a very common misconception.
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