Rodinal and Chemical Quality

[nworth]

I recently found a "Rodinal" kit from Photographers' Formulary that must be at least 12 years old. Most dry chemicals do not deteriorate much over time, and I needed some Rodinal for an experiment, so I mixed it up. Just to be sure, I at least inspected the chemicals by eye before I started. The p-aminophenol hydorchloride was light tan flakes. This looked like the practical grade chemical you used to find commonly in commerce. All the chemicals looked like they may have absorbed a very slight amount of water from the air through their containers (slightly deteriorated crystal structure on some crystals), but they seemed to be OK. When I dissolved the p-aminophenol, the solution was light tan, like the dry chemical. After adding the potassium hydroxide, it became a medium tan. I haven't tried the results yet, but I don't expect any problems.

The p-aminophenol hydrochloride that the Formulary is currently shipping is a dark reddish brown, almost black. It seems to have a lot of pot tar in it. When you mix it up (which is much more difficult), the solution is dark and usually has some insoluble scum. The "Rodinal" is correspondingly dark. The new material seems to work just as well as the old, but it doesn't look as nice. With all the past discussion about mixing Rodinal and the color of the result, I thought I would pass this along. The color is highly dependent on the quality of the developing agent, but the quality of the developing agent doesn't count for much.

 

[df cardwell]

How are the negatives ?

 

[gainer]

It takes a very small amount of oxidized Rodinal to make a large amount of water black. P-aminophenol is the basis of some very strong dyes. That is one reason you cannot tell how healthy yout Rodinal is by the color of the stock solution..

 

[nworth]

The developer works fine - just like Rodinal.