[pure-silver] Re: How Critical Is Wash Wate
- From: Jean-David Beyer <jeandavid8@xxxxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Thu, 10 Apr 2014 07:42:24 -0400
On 04/09/2014 11:49 PM, Richard Knoppow wrote:
>
[snip]
> Evidently ammonium thiosulfate in solid form is not very stable so
> its sold as a diluted liquid. I think I have formulas for fixing baths
> using it but would have to look. I am pretty sure Grant has some
> formulas in his book. Kodak published a formula for a "rapid" fixing
> bath, which I copy below. This is the kind that uses Ammonium chloride.
> It is not as satisfactory as an ammonium thiosulfate bath but works. The
> hardener can be left out if desired.
>
> Kodak Rapid Fixing Bath F-7
>
> Water (at about 50C or 125F)...............600.0 ml
> Sodium thiosulfate, crystalline............360.0 grams
> Ammonium chloride...........................50.0 grams
> Sodium sulfite, desiccated..................15.0 grams
> Acetic acid, 28%............................48.0 ml
> Boric acid, crystals.........................7.5 grams
> Potassium alum..............................15.0 grams
> Water to make................................1.0 liter
> Mix chemicals in order given.
>
> Note: If corrosion is encountered when using F-7 with stainless steel
> containers, it can be minimized by substituting 60.0 grams of ammonium
> sulfate for the 50.0 grams of ammonium chloride in the formula. When
> this is done the formula is known as Kodak F-9.
>
> Kodak warns against overly long fixing times for fine grain film or
> warm tone paper due to the bleaching action of the fixer. However, the
> bleaching effect is eliminated if the fixer is made neutral which can be
> done if the hardener is left out. I would then also leave out the boric
> acid and acetic acid. This is true of all rapid fixers.
>
I used to use F-9 as a rapid fixer especially for T-Max films and I
tried it for the Ilford rapid fixing process for the paper I was using
at the time. It is faster than F-6 fixer that I normally used, but not
as fast as Kodak (liquid) rapid fixer. I usually used ony half the
Potassium alum as I needed less hardening. The TMax films are fairly
hard, and the Kodak papers did not seem to need hardening.
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