[alt-photo] Re: dilution of pt/pd and oxalic acid and buffering

[Terry King]

Loris


Yes, but it is very easy



For the ideal neg I would say 1 : 4  Pt.


You can vary that amount to take account of reduced densities in the negative, i.e. to vary the contrast or to reflect the amount of shadow detail you need in the print.


We did have a shock recently when our platinum exposures suddenly reduced to two minutes rather than the usual fifteen. The difficulty was that we got solarisation in the shadows, in other words the potential contrast range of the printing process was reduced although the speed was increased. A quick check showed that increased buffering in the paper, presumably added calcium carbonate to reduce acidity, had had this effect. The solution was a soak in oxalic acid.


Terry





-----Original Message-----
From: Loris Medici <mail at loris.medici.name>
To: 'The alternative photographic processes mailing list' <alt-photo-process-list at lists.altphotolist.org>
Sent: Fri, 23 Jul 2010 7:45
Subject: [alt-photo] Re: dilution of pt/pd


Terry,

I was to mention this to Christina; she'll have to watch for solarization in
case of perfectly matching Fe and noble metal.

But that's something easy to take under control, right?

(1.) Use adequate amnt. of solution per coating area
(2.) Do not overexpose
(3.) Add a little Pt (1:5)

Regards,
Loris.


-----Original Message-----
From: alt-photo-process-list-bounces at lists.altphotolist.org On Behalf Of
Terry King
Sent: Friday, July 23, 2010 9:38 AM
To: alt-photo-process-list at lists.altphotolist.org
Subject: [alt-photo] Re: dilution of pt/pd


...
The dilutions of 20% for the sodium tetrachloropaladate, potassium
tetrachloroplatinate and ferric oxalate enable me to achieve prints which
reflect the qualities of the negative .
...

_______________________________________________
Alt-photo-process-list | http://altphotolist.org/listinfo