[pure-silver] Re: PMK and MCS
- From: Christopher Woodhouse <chris.woodhouse@xxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Sun, 30 Apr 2006 07:36:33 +0100
Unfounded....?
In prior years I have posted experimental results of using classic and
alkali based processes and their effect on fibre based washing efficiency. I
have tried 3 different alkali fixers with the same positive results:
In brief, I found that prints processed in a plain water stop bath and an
alkali fixer washed in the same time as an acid fixed print that had been
soaked in hypoclear. Used in conjunction with hypoclear, further
improvements to the wash time were experienced. (Residual Thiosulfate was
tested with freshly made HT2 solution against a calibrated chart.)
In addition with alkali fixers, you can go straight from fixer to selenium
toning without issue. I noticed Selenium toner takes a nose dive and
precipitates grey sludge after acid based fixing, unless extensive washing
of the fixed print is undertaken first.
Overall, the amount of water and time saved is significant.
BTW, at no time did I experience staining or fogging. My highlights are
clean and white. I'm using Agfa MCC, which is prone to go off at the
slightest provocation too.
I was playing with prescysol and was trying to maximise the stain by using
alkali stop baths, fixers and developers, but experienced chalky deposits on
the film (I believe EDTA is the magic ingredient that dispels this, RS and
RK will know for certain). After all the faff, I discovered that Fuji films
refused to stain with this formula.
Chris Woodhouse ARPS
On 28/4/06 20:03, "Ryuji Suzuki" <rs@xxxxxxxxxxxxxxx> wrote:
> From: David Foy <dfoy@xxxxxxxx>
> Subject: [pure-silver] Re: PMK and MCS
> Date: Fri, 28 Apr 2006 09:35:58 -0600
>
>> I read and re-read and re-read Anchell and Troop, who I believe
>> popularized the idea of avoiding acid fixation, to try and find out why
>> they advocate against it. The only thing that I could find were
>> suggestions tucked away here and there that modern films have higher
>> iodine content than earlier films, and there is apparently something
>> about this, having to do with how long things take, perhaps too long
>> wash times, that lies behind the preference for alkaline processes
>> straight through from start to finish. Perhaps I missed something. I
>> know of no professional photochemist who sees it as an issue.
>
> Don't try to make much sense out of that book. (In my previous post, I
> implicitly said this.)
>
> That modern emulsions contain "higher" iodide content may or may not
> be true. In old technology, the amount of iodide changed a lot of
> variables and emulsion engineers didn't have much freedom. But today's
> emulsion engineers can design grain structure in multiple layers, and
> the thin ones are only a few molecules thick. The place and amount of
> iodide within crystal structure has great influence in efficiency of
> making latent image centers, efficiency of spectral sensitization,
> etc., but these have nothing to do with acid v. alkaline fix process.
>
> In research of image permanence, it is often important to test with
> two kinds of emulsions, one with iodide and the other without any
> iodide. Emulsions containing no iodide are usually more vulnerable to
> oxidative attacks unless some other means of protection is given to
> the silver image. Again, this is irrelevant to acid v. alkaline fix
> debate.
>
> While I believe there are some advantages to neutral to weakly
> alkaline fixing bath for b&w processing, many debates on the topic are
> on unfounded basis.
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--
Regards Chris Woodhouse
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