[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: Extravagatype and Na2
If I read you right this is the answer: Na2 can only be used so far with
the XTP process as it will precipitate out at high concentrations. Just
discovered this working on some museum archive negs.
Call me at 505-474-0890.
At 07:47 AM 5/8/2002 -0400, you wrote:
> I originally thought that this precipitate was (NH4)2PtCl6 from exchange
>with ammonium ferric oxalate. I think I read somewhere that the ammonium
>salt is much less soluble. Your comment that the yellow precipitate is the K
>salt is interesting. Is solubility data for the Na, K, and ammonium PtCl6
>I've used Na2PtCl6 in extravagatypes and coated normally despite the
>precipitate. It still gives a contrast boost despite some of the chemistry
>dropping out of solution. I must admit that coating a slurry bothers me and
>must be wasteful. I doubt the precipitated salt is distributed evenly and
>participating normaly in the image formation.
>----- Original Message -----
>From: "Jeffrey D. Mathias" <email@example.com>
>Sent: Wednesday, May 08, 2002 6:25 AM
>Subject: Re: Extravagatype and Na2
> > Erich Camerling wrote:
> > > ... Sodium Chloroplatinate ( Na2PtCl6 , shortened Na2 ) as a contrast
> > > agent in standard Pt/Pd printing ...
> > > But when I mix ( for instance ) 3 drops Ammonium Ferric Oxalate
> > > ( 40g/100 ml H2O ) with 2 drops K2PtCl4 ( 20g/100 ml H2O ) and 1 dro
> > > Na2 ( 20g/100 ml > H2O ) I immediately get a sediment ( yellow , I
> > > suppose K2PtCl6 ( nearly > unsoluble ))
> > > Richard wrote me that I was the first who mentioned this problem.
> > > Other alt-photo-list members wrote about Na2 in PALLADIUM printing.
> > > Has anyone of this group tried Na2 in Extravagatype ? And what was the
> > > result ? I'm very interested.
> > Your problem is that K2PtCl6 is only very slightly soluble in water.
> > The metal double salt Richard wrote about for use to control contrast is
> > Na2PtCl6. These are very different.
> > The yellow sediment and insolubility in water are a good indication that
> > you did have K2PtCl6. K2PtCl6 can also be found as an impurity in
> > K2PtCl4 (the double salt typically used for platinum printing). The
> > best ways to avoid K2PtCl6 is to have a good manufacturer or source of
> > the material and to not store or use it at temperatures in excess of
> > 140F, especially in the presence of sodium.
> > --
> > Jeffrey D. Mathias
> > http://home.att.net/~jeffrey.d.mathias/