Home made Rodinal chemistry question...

[Harry Stevens]

Well I am no chemist that's for sure but I have a question. When making up my own made Rodinal developer I use a Sodium Metabisulfite and Sodium Hydroxide mix to make up a sodium sulfite solution my question is how long does it take for it to be treated as sodium sulfite. I know it gets very warm on mixing and I then leave it for 24 hours before using, do I have to wait that long or does it convert into sodium sulfite instantly ?.

 

[John Wiegerink]

Well I am no chemist that's for sure but I have a question. When making up my own made Rodinal developer I use a Sodium Metabisulfite and Sodium Hydroxide mix to make up a sodium sulfite solution my question is how long does it take for it to be treated as sodium sulfite. I know it gets very warm on mixing and I then leave it for 24 hours before using, do I have to wait that long or does it convert into sodium sulfite instantly ?.

I tried to make my own Rodinal and came to the conclusion it was certainly no better than the available commercial stuff and kind of a pain to make. For what you end up using, as far as volume of developer goes, and the shelf life of commercial Rodinal I will not go through the hassle again. Only if it were ever taken off the market would I try to make it and then I have found a just as good alternative that is easier to make and the results are just as good if not better. So, for me, I'll take the easy way out and just buy it. My last bottle is over four years old, not even half gone and still working like a champ. That said, I think you should give it a try to see for yourself if it's really worth the hassle and not take my word for it. Have fun! Oh, I would answer your question, but I'm away from my darkroom and notes at this time. Sorry!

 

[Gerald C Koch]

The reaction is essentially instantaneous.

HOWEVER your recipe seems a bit strange. Usually the PAP or PAP HCl are dissolved in the hydroxide solution. Then the metabisulfite is added. The hydroxide and metabisulfite are never directly mixed together. I don't know what you are getting but it isn't Rodinal.

John is right mixing a ordinal type developer is not the same as say mixing D-76. Among other things the order of the addition of the ingredients must be strictly followed. If you are unfamiliar with chemistry it would be best to just buy one of the existing versions on the market. As pointed out you are not really saving any money mixing your own.

 

[Ian Grant]

Rodinal uses p-Aminipheol free base and more Metabisulphite than you can get tints solution using Sodium salts. While in theory the reactions may be instant it actually takes time for the equilibriums to stabilise so you maŷ need to adjust pH the next day.

You can make Dr Momme Andresen's concentrated. P-Aminophenol developer quite easily, he published the formula himself, however it's not Rodinal although it has similarities. It's possible to get closer to modern Rodinal but it's far more work and effort not really worthwhile except commercially.

Ian