[pure-silver] Re: a recent problem with fine dust on negs

Tim Daneliuk wrote:

Alan Sugiyama wrote:

Janet,  Could it be your fixer?  I had to resort to filtering (thru
coffee filters) my mixed fixer before my similar problem was cured.  All
houses and their plumbing are unique and they all contribute to
sediment, rust, from your spigot.  If fixer is contaminated, it will fix
and harden the sediment to your emulsion.  Good Luck!

Alan Sugiyama
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I was about to suggest something similar.  It almost looks like some
of the chemistry was not completely dissolved - a condition caused
by mixing the chemistry with water that is too cold.  For powdered
chemicals, I take distilled water in gallon jugs and immerse them for
20 minutes in a sink full of hot water.  Once the distilled water is up
to temp I then mix the chemistry as recommended.  Failing to do this -
or not using the proper amount of water - will cause the chemicals to
either not complete dissolve and/or precipitate out when the solution
cools.
The chemical formulae with which I am familiar give the amounts of each ingredient, the order in which to mix them, and the initial temperature of the water required. Even then, it is sometimes difficult to get a proper solution.
First, I have a 5 micron filter in the water line. This does nothing for dissolved things, but gets out the particles. IIRC, you want to mix sodium thiosulphate fixer with water at 125F and do it rather quickly before the water temperature goes down. It takes several minutes to get all that to dissolve. Dissolving it lowers the temperature of the water considerably, so getting the sulphite to dissolve also requires a lot of stirring. Basically, it probably takes me 20 to 30 minutes to do a good job mixing up F-6 fixer. I do not use distilled water for it.
For 35mm work, I do use "distilled" water for the developer and stop bath. Also for FotoFlow, that I make up at 5/6 the recommended strength.
The hardest thing to dissolve that I have is benzotriazole. I dissolve it in cheap house-brand vodka, and then dilute the mix to 1% solution. 

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