It is not uncommon to hear of 30 to 40 years old Rodinal working as when new. My own experience is with 25 yo stuff, still have some of it. What would be awesome, is someone finding old full bottles pre WWII and developing film with that!
Originally Posted by heterolysis
I have found Parodinal to be long-lived as well, provided it is prepared with the correct chemicals at the correct concentrations. My oldest samples are now two years, and showing no signs of deteriorating.
Edit: BTW the reason why shaking up the bottle helps, is maybe because it re-dissolves some of the crystallised aminophenolate, i.e. it replenishes the active developer in solution. Good Rodinal must always have a few crystals lying in the bottom of the bottle, and when decanting into other containers, one must transfer the crystals too. Otherwise, the developer will crash sooner. If you suspect oxidation, one should not use only the top layer of the liquid. Diffusion in a viscous liquid such as Rodinal is very slow, and it can happen in reality that the replenishment simply does not take place via diffusion over the time frame you mention through a liquid column a few inches high.
Rodinal proper contains at least two salts, namely potassium sulphite and potassium aminophenolate, in addition to potassium hydroxide. There could also possibly be chloride and bromide, depending on the formula. Two things are important: The aminophenolate in solution must be close to or exceed 0,5 moles/L, and the sulphite must stay in solution. To get this, sodium cannot be totally replaced for potassium, and the most one can get away with is ca 1 part of sodium per one part of potassium. I don't know what the current R09 formula contains exactly, but I am pretty sure it is based on potassium chemistry. The DIY formulas such as in the Darkoom Cookbook suggest using 4-aminophenol hydrochloride, and sodium hydroxide with potassium metabisulphite. This results in an additional amount of chloride in the developer, but that is of course greatly diluted in use. In the Parodinal formula, it is not chloride, but acetate that forms. In metonal (from metol), it is sulphate. In practice, I have found as yet no effect on how and what forms the main constituents are added, as long as they are there in the final product. In other words, after all reactions have taken place (acid-base neutralising etc) there should be excess hydroxide, sulphite and aminophenolate. The extra baggage of chloride, acetate or whatever else, is mostly inconsequential. When using sodium hydroxide, the sulphite must be potassium. And vice versa. One should not filter home preparations. Rather, one should strive to get the quanities of chemicals correct, and leave the precipitate to form and stay there, as it is responsible in part for the longevity.
Last edited by dorff; 07-30-2013 at 04:48 AM. Click to view previous post history.