Liam Lawless (lawless@vignette.freeserve.co.uk)
Sat, 30 Jan 1999 00:49:38 +0000
Hi Steve,
Sorry, Steve, I must have misunderstood - I thought your shadows were
reasonably correct. OK, looking back at the tests for a Darkroom User
article that I did a couple of years ago, it seems that chromium does not
give much of an increase in the shadows. Of the several intensifiers I
tested then, I am now recommending copper & silver, which gives permanent
results and the greatest increase in the shadows. It can be used
repeatedly, and each time is supposed to triple the amount of silver
originally present. (In practice, this roughly doubles all densities.)
In a hurry tonight, so I'll just copy out the relevant part of my original
article:
Copper and silver intensifier was, apparently, commonly used with collodion
negatives, but was not so satisfactory on gelatin emulsions until the method
was improved in the 1920s (by Luther and Schrieber [1923] and G. Zelger of
the Pathe-Cinema Laboratories [1924]). Despite using copper, the image is
intensified with silver and intensification should produce exactly three
times the amount of silver originally present. The process may be repeated
and again trebles the amount of silver; in this manner it is possible to
obtain sufficient contrast in images which exist as mere ghosts. (But keep
an eye on highlight densities, and fog levels!)
Zelger's Formulae
Sol. A
Copper sulphate (cryst.) 10g
Acetic acid (glacial) 56ml
Water to 1000ml
Sol. B
Potassium iodide 10g
Ammonia (.880) 92ml
Water to 1000ml
Sol. B
Silver nitrate 2.5g
Sodium acetate 10g
Distilled water to 1000ml
The negative is first bleached in equal parts of A and B. A little heat is
generated on mixing; allow to cool before using. The bath should be
slightly acidic; if it does not redden blue litmus add further acetic acid
until it does. The solution is quite stable and can be kept for re-use
until exhausted.
Bleaching is quite slow and about 10 minutes should be allowed. When
complete, the image will be yellowish by reflected light from the emulsion
side. Bleaching converts the silver to silver iodide, and also deposits an
equivalent amount of cuprous iodide onto the image. After washing
thoroughy, darkening follows with solution C. This causes the conversion of
the cuprous iodide into silver iodide, and also the precipitation of
metallic silver. The process is completed, after further washing, by
redevelopment which reduces the silver iodide to silver. Or, if the image
is too dense, it may be reduced -before it is redeveloped - by a 2% hypo
solution.
Viewed from the emulsion side, negatives look greyish after the silver bath
and while it clears to some extent as redevelopment proceeds, it does not do
so completely because it is partly due to silver deposited on the surface of
the film. Silver iodide develops very slowly, but it can safely be inferred
that redevelopment has finished when no further change is noticed over a
period of 5 minutes.
Silver nitrate combines with gelatin and is not removed by washing, and this
in turn combines with chlorides in tap water to form silver chloride which
is then reduced to silver on developing, increasing fog. Clerc suggests
immersion in a saturated alum solution (i.e. 9.6% aluminium potassium
sulphate) before the silver bath in order to prevent the combination of
silver nitrate and gelatine. Alternatively, films can be treated after the
silver barth with 1% ammonia solution to remove any silver chloride that has
formed.
Well, Steve, if you don't like this one I can send more (when not so busy!),
but it really is an excellent intensifier if your negs are extremely thin.
Liam
-----Original Message-----
From: Steve Shapiro <sgshiya@redshift.com>
To: lawless@vignette.freeserve.co.uk <lawless@vignette.freeserve.co.uk>
Date: 29 January 1999 23:51
Subject: Re: Amidol Redeveloper
>Subject: Re: Amidol Redeveloper
>
>
>>Hi Judy,
>>
>>Steve said
>>that his shadows were about right, but that the highlights were thin
>because
>>of
>>exhausted developer. However, I forgot to mention the most important
>point,
>>that redeveloping in amdol will not increase density unless in conjunction
>>with something like chrome intensifier... hopefully he'll read this.
>>
>>
>>Liam
>
>
>To be honest, I don't remember what I said; but what I have are well
exposed
>pieces of [4X5] film, but the developer became exhausted without my paying
>attention and the density of the shadow detail, while is there, is so
slight
>it takes too much care to make prints. I want to 'redevelop' to a point
>where I'm not going through three processes, forty minutes per print to get
>my pictures of the Monterey San Dunes in the Fog, Dunes that have been --
>now -- ecologically reclaimed to their overgrown pre-historic state. My
>photos show actual sand, with some growth; and not it's back to the
original
>ranch site that can't be compared to the photographic extravaganza it was,
>then.
>
>Then, to make dense negs ... maybe I should simply go to the inner neg and
>forget the silver prints; I could use these and .... aw forget it.
>
>So, if I use the bleach part of the sepia toning kit, then stick the washed
>negs into developer, I'll have a second go of it, right?
>
>Or, if I use the Ferrocynide with What? and get a clear piece of film with
>halides to go into developer; and you suggested the ferrocynide at a seven
>times dillusion, right?
>
>Steve
>
>Sorry to seem like I'm in a daze; but I am. I'm caring for a sick wife and
>passing spare time babbling over this network.
>
>
>
This archive was generated by hypermail 2.0b3 on Sat Nov 06 1999 - 10:06:45