[pure-silver] Re: Rodinal
- From: `Richard Knoppow <dickburk@xxxxxxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Fri, 17 Apr 2015 19:18:24 -0700
On 4/17/2015 5:49 PM, Janet Gable Cull wrote:
Thank you, all!
I found a discussion of the Rodinal formula along with some
variations at:
https://www.flickr.com/groups/rodinal/discuss/72157633978523578/
This may be of interest to those who would like to mix something
up to try. The formula given uses lithium hydroxide, which I have seen
mentioned in old books as being used by Agfa early on. But there is also
information for a formula using potassium hydroxide which is much
cheaper and is probably what Agfa used during most of the production
life of the product. Potassium hydroxide is superior to sodium
hydroxide for this application because it will dissolve to a higher
concentration. The paraminophenol is dissolved to a slightly
oversaturated state. When the solution is cooled some of the
paraminophenol will come out of solution and form crystals at the bottom
of the container. This is necessary for long life although the late
commercial product did not have the crystals in it. Since there is very
little sulfite the solution tends to turn brown rather quickly.
However, this evidently does not interfere with its performance.
Please note that Rodinal Special is not a variation on Rodinal, it
uses a completely different developing agent.
Rodinal was the first packaged developer, going on the market in
1891.
--
Richard Knoppow
dickburk@xxxxxxxxxxxxx
WB6KBL
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