[alt-photo] Re: tintype

[etienne garbaux]

Cor wrote:

>I am not buying this, all the stuff I have read have never mentioned 
>this (I would be gladly corrected by you if you have scientific 
>references), and my own experience tells me that development is 
>extremly fast, an overexposed plate pops up in just 1-2 seconds 
>after covered by developper..granted it might be surface development 
>only, do not know that.
>
>Also fixing with fresh standard rapid fix shows that the completly 
>unexposed parts are visually fixed in 20-30 seconds, another in 30 
>seconds are added for safety, leaving a very clear collodion layer 
>in the (unexposed)  deep shadows.

If you search the conservation literature, you will find a number of 
references questioning the archivality of thiosulfate-fixed collodion 
images.  I may have several of the papers around here somewhere, but 
if I wanted them I'd do a literature search rather than trying to 
find them.  And yes, the development is all on the surface (several 
conservation articles present electron microscope sections of 
collodion photos that show this very clearly), because by the time 
development occurs the developer cannot penetrate the collodion very 
well or very far.  For this same reason, neither can the fixer -- and 
therein lies the problem.

Feel free to use thiosulfate, and I understand that quite a few 
current practitioners do.  But as I said before, it won't be known if 
it really did the job until we are long dead.  (Perhaps not such a 
bad thing, actually -- IMO, relatively few photographs deserve to 
survive for centuries.)  The collodion negatives, prints, ambrotypes, 
and tintypes I made starting in the late '60s are all doing fine so 
far (all fixed in KCN).

Best regards,

etienne