[alt-photo] Re: tintype

[etienne garbaux]

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