Alan Johnson
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It is well known that Rodinal [generic term] can deposit crystals, IMO potassium aminophenolate, generally thought to be good crystals that maintain its strength.
Here I discuss a different deposit found in oxidized old Rodinal.
I had some Rodinal 20 years old that worked well and about 5 years ago put some in a 100ml glass bottle with a plastic stopper. Recently I got a blank film from a 1:25 solution of this. There was a non-crystalline deposit in the bottle which I removed for examination [pic].
To all this deposit was added 5g sodium hydroxide and 50ml water. With heating most of it dissolved. A film leader was placed in the cooled solution for 20 min, then fixed. It was clear apart from slight fog. This shows that the deposit from this very old Rodinal was not the active potassium aminophenolate "good crystals" mentioned above. It was very likely some kind of oxide formed from air diffusing in through the plastic stopper over 5 years.
So it seems quite likely that Rodinal only lasts until all the preservative sulfite in it is used up.
Here I discuss a different deposit found in oxidized old Rodinal.
I had some Rodinal 20 years old that worked well and about 5 years ago put some in a 100ml glass bottle with a plastic stopper. Recently I got a blank film from a 1:25 solution of this. There was a non-crystalline deposit in the bottle which I removed for examination [pic].
To all this deposit was added 5g sodium hydroxide and 50ml water. With heating most of it dissolved. A film leader was placed in the cooled solution for 20 min, then fixed. It was clear apart from slight fog. This shows that the deposit from this very old Rodinal was not the active potassium aminophenolate "good crystals" mentioned above. It was very likely some kind of oxide formed from air diffusing in through the plastic stopper over 5 years.
So it seems quite likely that Rodinal only lasts until all the preservative sulfite in it is used up.
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