[alt-photo] Re: tintype

[Vedos]

Hi,
Collodion is not non-permeable during the process because it is kept wet. That's why the process is wet plate collodion, it doesn't work if the collodion dries. The plate is not "essentially dry" during fixing -- it is very wet. The normal method is to rinse the plate after developing, and then immediately fix the plate.

For a fixer, sodium or ammonium thiosulfate is perfectly fine... there's no reason to use potassium cyanide, especially for negatives, but for ambrotypes cyanide will introduce a little more punch, they say...

Best regards,
Jalo


-- If you only look at what is, you might never attain what could be --

V E D O S
Alternative Photographic Processes
Satakunta University of Applied Sciences
vedos at samk.fi
http://vedos.samk.fi
http://www.samk.fi
________________________________________
From: alt-photo-process-list-bounces at lists.altphotolist.org [alt-photo-process-list-bounces at lists.altphotolist.org] On Behalf Of etienne garbaux [photographeur at nerdshack.com]
Sent: Wednesday, November 03, 2010 6:47 PM
To: The alternative photographic processes mailing list
Subject: [alt-photo] Re: tintype

Richard wrote:

>Are you sure potassium cyanide is necessary for fixing wet plate? My
>understanding is that ammonium thiosulfate (rapid fixer) has
>sufficient power to fix out the silver iodide. Thiocyanate would be
>even more powerful but still safe compared to the cyanide.

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.  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




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