Re: Fixing of a kallitype

Some comments.

1. Most of the sources you mention make virtually the same
recommendation, i.e. a 5% solution of sodium thiosulfate plus a
little something else to make the solution slightly alkaline. Making
the solution slightly alkaline reduces bleaching of the silver metal
that can take place when fixing in acid solutions.

2. There is a balance in kallitype. Fixing too long with a very
strong fixer, especially if acidic, will cause bleaching of silver
metal; inadequate fixing, either because of length of time or
strength of the fixer, will not remove the residual silver salts.

3. Kallitype prints that are toned before fixing with gold, palladium
or platinum bleach very little, if any, during fixing. So if you
always tone before fixing you can use a stronger fixer and eliminate
the carbonate or ammonia that makes the fixer alkaline. I assume that
some people will want to tone after fixing with selenium, however, so
my recommendation is for a moderate strength solution made slightly
alkaline.

4. Because of the fact that the silver salts are on the surface of
the paper, rather than embedded in a gelatin solution as in
contemporary silver gelatin papers, the fixing solution reaches these
salts immediately without having to pass through gelatin. For this
reason fixer for kallitype can be weaker than what is typically used
for silver gelatin papers, and fixing times can be much shorter.

5.Don't anguish over discrepancies and inconsistencies in the
literature. Everybody could be wrong so make your own tests for
residual silver nitrate and residual hypo in the print. If your tests
don't find any residual hypo or silver nitrate I think it is safe to
assume that your processing technique is sound. If you do find
residual hypo or silver nitrate back to the drawing board.

Sandy

>Dear members,
>
>When I started reading articles (papers ?) about fixing I got into disorder.
>At first because every author gives a different quantity of sodium
>thiosulfate per liter and a different receipe and a different time.
>Sandy King: 50 g/l + 10 g Na2CO3 + 2g Na2SO3
> time: 240 sec. or 2 x 120 sec.
>Judy Seigel: 55 g/l + 10 ml ammonia
> time: 120 sec.
>B & S : 25 g/l time: 15 sec.
>Keepers of : 50 g/l + 6 ml ammonia
> Light time: 300 sec.
>Dick Stevens: don't know what he is saying about it .
>WHAT IS CORRECT ?
>Second: Do they use
> sodium thiosulfate : Na2S2O3 CAS: 7772-98-7
>or sodium thiosulfate.pentahydrate : Na2S2O3.5 H2O
> CAS: 10102-17-7 . Most common.
>The same with:
> sodium carbonate : Na2CO3 CAS: 497-19-8
>or sodium carbonate.monohydrate : Na2CO3.H2O
> CAS: 5968-11-6
>or sodium carbonate.decahydrate : Na2CO3.10 H2O
> CAS: 6132-02-1
>or sodium carbonate.hydrate : Na2CO3.aq
> CAS: 24551-51-7
>WHAT IS THE RIGHT STUFF ?
>Third: What is the concentration of the used ammonia ?
> Is it 5%,10%,15% or even more ?
>( In the Netherlands 5% is usual as household ammonia but you can also buy
>15% )
>TIP : sodium thiosulfate.pentahydrate (CAS 10102-17-7)
> cools on dissolving
> sodium thiosulfate anhydrous (CAS 7772-98-7)
> heats on dissolving
>(SPSE Handbook of Photographic Science and Engineering
> page 528 ISBN 0-741-81880-1 (1973)
> ISBN 0-685-20939-3 reprint
> ISBN 0-608-17768-7 reprint )
>But the most confusing to me is the (low) concentration of
>sodium thiosulfate.
>As a student I learned that fixing in standard photography is
>a very complicated chemical process.
>First step: 2 AgBr + Na2S2O3--> 2 NaBr + Ag2S2O3
>
>(insoluble)
>Second step:
> Ag2S2O3 + Na2S2O3 <--> 2 Na(AgS2O3) and
> Ag2S2O3 + Na2S2O3 <--> Na2Ag[Ag(S2O3)2]
> (slightly soluble)
>Third step :
> Na(AgS2O3) + Na2S2O3 <--> Na3[Ag(S2O3)2]
> Na2Ag[Ag(S2O3)2] + Na2S2O3 <--> Na4[Ag2(S2O3)3]
> Na2Ag[Ag(S2O3)2] + Na3[Ag(S2O3)2] <-->
> Na5[Ag3(S2O3)4]
>Because all the reactions in the second and third step are
>equilibrium reactions you need a large excess of sodium thiosulfate Between
>18 C and 21 C (for Americans : between 64 F and
> 70 F ) the optimum is a 40-50 % solution.
>(Photography for the scientist. Ed: Charles E.Engel
> 1968. Academic Press N.Y.
>page 260. No ISBN
> Library of Congres Catalog Card number: 66-16698. )
>
>Mostly used : 20 % solution
>WHAT IS THE REACTIONMECHANISM OF FIXING
>IN KALLITYPE ?
>IS FIXING OF A KALLITYPE SO TOLERANT THAT IT DOESN'T MATTER HOW YOU'LL DO IT
>?
>
>I am really interested in soundly based answers,so please don't
>tell me stories with : "when I remember well.. " or "I am not quite
>sure... " or "I believe that..." etc.
>There are already (too) many articles whit presumptions,
>suppositions and idle thoughts on internet.
>Kind regards
>Erich
Received on Sat Dec 13 09:05:40 2003