[alt-photo] Re: tintype

[C.Breukel at lumc.nl]

> ----- Original Message -----
> From: "etienne garbaux" <photographeur at nerdshack.com>
> To: "The alternative photographic processes mailing list"
> <alt-photo-process-list at lists.altphotolist.org>
> Sent: Tuesday, November 02, 2010 6:42 PM
> Subject: [alt-photo] Re: tintype
> 
> 
> > is Kodak Fixer.  For real collodion tintypes, you would
> > need to use potassium cyanide.
> >
> > etienne
> >
>     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.
>     However, I am just asking that, I agree with your
> analysis of the Rockland process. Tintype is not a reversal
> process although its a direct positive process. It relies on
> the reflectivity of the silver image rather than its
> density.
> 
> --
> Richard Knoppow
> Los Angeles, CA, USA
> dickburk at ix.netcom.com
> 
> _______________________________________________
> Alt-photo-process-list | http://altphotolist.org/listinfo

Potassium Cyanide is absolutely NOT needed for producing Tintypes, "ordinairy" rapid fix or plain hypo work equally well but have different properties. It might be that in the reenactment scene KCN is the only accepted fixer. 

The differences between said fixers it mainly the resulting image colour, the KCN fixer being the warmest (café-au-lait), KCN gives somewhat more punch, deeper blacks, also because it will bleach a silver image (leaving a plate in KCN will eventually completely bleached away). KCN fixes very fast, has a high capacity and is said to wash out very fast (have yet to see a real proof of that often mentioned fact).

OTOH KCN is a deadly toxic compound and in contact with acid it will produce HCN gas which will kill easily..so it is up to each user to decide on the pro's and con's 

On the Rockland kit: as mentioned before it is a bit of a misnomer, and thusfar I have read mainly bad things about it..sorry..

Best,

Cor