CCBaggett@aol.com
Date: 07/23/02-06:43:45 PM Z
Chris,
I found what you asked for in the 1970 Revised edition. Here is what
#687 says:
687. Heavy Intensification with Copper and Silver. A method which has been
used for a very long time, consists in treating the negative in a solution of
cupric bromide in which the silver is converted into bromide and at the same
time fixes an equivalent amount of cuprous bromide.
The negative, after rinsing, is transferred to a solution of silver
nitrate, some of which is reduced metallic silver by the bromide; this silver
is thus precipated with an equivalent amount silver bromide in the image
along with the existing silver bromide according to the following equations:
Ag+ CuBr2 -> AgBr+ CuBr
CuBr+ 2AgNo3 -> Cu(No3)2 + Ag + AgBr
After washing, and reducing the silver bromide, the amount of silver is
exactly three times that originally present(W.deAbney, 1877). During washing,
the cuprous bromide is partially redissolved or re-oxidized and so escapes
reaction.
The method has been improved by Luther and Schreiber (1923), and by G.
Zelger (1924), by using in the first operation a solution which deposits in
the image not cuprous bromide but a cuprous salt which is absolutely
insoluble and non-oxidizable, such as cuprous thiocyanate or cuprous iodide.
As before, the density is exactly trebled by intensification; it may
be trebled again by repeating the process, and thus sufficient contrast may
be obtained to print an image which exists as a mere ghost, as is sometimes
obtained with films in which regression of the latent image has occurred.
Care must be taken to avoid uneven action or reticulation of the
gelatine if the process is repeated more than once.
The "bleaching" bath(which, as a matterof fact, gives a yellow
image)is prepared by pouring solution (A) into solution(B)-
Solution A
Copper sulphate, cryst. 5 g
Acetic acid, glacial 28 ml
Water to 500 ml
Solution B
Potassium Iodide 5 g
Ammonia 0.880 50 ml
Water to 500 ml
Heat is generated when the solutions are mixed, and the bath must not be used
until cool.The mixed solution, which is clear blue in colour, should be
slightly acid; if it is not, a little acetic acid must be added until blue
litmus paper is faintly reddened by it. This solution is quite stable and may
be used until exhausted.
The negative is immersed in it until the image becomes yellow
throughout its thickness. After thorough washing it is blackened in a
solution containing 0.25 per cent of silver nitrate to which about 1 per cent
of sodium acetate has been added (so preventing the copper nitrate formed
during the reaction from attacking the silver).Before treatment with the
silver nitrate, the negative may be immersed in a saturated solution of alum,
so preventing combination silver nitrate with the gelatine.
The silver salts, other than silver iodide (chloride precipitated in
the gelatine due to the use of ordinary water and silver nitrate combined
with the gelatine), are removed by immersion for about two minutes in a bath
containing about 1 per cent of ammonia, which has no action on the silver
iodide.
The process is completed by reducing the silver iodide to the metallic
state by means of a solution of sodium hydrosulphite containing a little
sodium bisulphite, or by meansof an amidol developer made alkaline with
sodium carbonate.
Hope this what you were looking for.
Cheers,
Charlie
In a message dated 7/23/02 2:03:12 PM Eastern Daylight Time,
zphoto@montana.net writes:
> (I just love the internet...no sooner asked than given)
> Philippe,
> This is what Clerc says under #832, Dye toning: "The mordanting can
> be
> carried out by the formation of silver iodide and cuprous iodide using the
> intensifying bath described in #687, due to G. Zelger, 1924." Does this
> help?
> Thank you so much for looking into this.
> Chris
> ----- Original Message -----
> From: "Philippe Monnoyer" <philippe.monnoyer@skynet.be>
> To: <alt-photo-process-l@sask.usask.ca>
> Sent: Tuesday, July 23, 2002 12:52 PM
> Subject: Re: Clerc's no. 687
>
>
> > Christina,
> >
> > I have the original version in french of Clerc's book.
> > #687 is about washing.
> > What kind of intensifying bath are you refering to ?
> > In Clerc's book, we have:
> > Intensification:
> > - for Latent Image
> > - for Negs
> > - by silver deposition
> > - localised
> > - intensive
> > - optical
> > - by powder
> > - of prints
> > - of carbon prints
> >
> > Make your choice.
> > I don't know what you're looking for.
> >
> > Philippe
> > Belgium
> > > Unfortnately, I am in Minnesota right now with no access to a library
> that
> > > has technical photo books. Does anyone on the list have Clerc's
> > > Photographic Theory and Practice who can give me the info in #687? I
> am
> > > looking for what is said about an intensifying bath (still on this
> > > mordancage quest).
> > > Chris
> > >
> > >
> >
>
>
This archive was generated by hypermail 2.1.5 : 09/19/02-11:11:01 AM Z CST