[alt-photo] Re: tintype

[C.Breukel at lumc.nl]

> 
> Because of the non-permeable nature of collodion, and the fact that
> fixing is done when the plate is essentially dry and the pores in the
> collodion are closed, the most powerful fixer available is
> indicated.  

??
Never heard this one, could you elaborate Etienne?

The cyclus I (and anybody else I heard, seen or read about) use is pour
the collodion salt emulsion on a plate (be it Trophy aluminium for Tin
type or glass for ambrotype) let it dry up just a bit, put it in the
sensitizing tank with silver nitrate, clean and place in holder and
expose.

Develop with FerricSulphate/Acetic acid, stop with water , rinse for 30
sec. with fresh water and the plate is than placed in the KCN fixer.

So the plate stays wet all the time, I do not see why the pores
should/could close and plate would be dry. That occasionally can happen
if you life in a very dry climate or used to much time between exposure
and development.

On ammoniumthiosulphate: it definitely clears a plate, and most people
fix for twice that clearing time. Granted it's unknown what realy
happens, but I am not too worried.

Best,

Cor



It is true that some modern practitioners believe
> ammonium thiosulfate is adequate.  There has been some literature in
> the conservation world questioning that belief.  I guess we'll have a
> better idea in 150 years.  Until then, I, for one, will use potassium
> cyanide.
> 
> Best regards,
> 
> etienne