>
> >All that needs to be done is to place a drop of nitric acid on
> >a dark portion of the print, the platinum will resist bleaching and the
> >Kallitype will go paper white almost instantly.
>
> One way to check this for those who have access to the equipment is to
look
> at the photo in a scanning electron microscope with an energy dispersive
> x-ray spectrometer. These are quite common in universities. Provided
that
> the print is not too large to fit in the vacuum chamber one can analyse
the
> metal component of the image in a non destructive way. I tried this with
a
> small print that I thought was a palladium print. I didn't find any Pd
but
> I did find silver and iron. The print doesn't look like a silver gelatin
> print so I had to conclude that it was a Kallitype due to the fact that
the
> image appears to be in the paper and the small amount of iron present from
> the sensitizer. I would guess that the print was probably made pre WWII.
> If my conclusion is correct about it being a Kallitype then it has
survived
> quite well since I see no signs of fading.
>
>
> --------------------------------------------------------
> John Hudak hudakjm@mcmaster.ca
> Electron Optics
> Brockhouse Institute for Materials Research
> McMaster University
> Hamilton, Ontario, Canada
>
This certainly tends to support the suspicion that surviving kallitypes are
often categorised as platinum prints. Can anyone suggest a non-destructive
method of testing with less esoteric equipment? (Common though scanning
electron microscope with an energy dispersive x-ray spectrometers may be I
can't find one in my junk cupboard!)
One idea that did occur to me as I was bicycling home today (more my level
of technology) was that it may be possible to test chemically (but
possibly destructively) if kallitypes are likely to fade due to the presence
of iron(III); I think that this reaction would be greatly accelerated by the
addition of EDTA (such mixtures I think being used as bleaches in some photo
processes.) Mind, I'm very firmly an ex-chemist these days, so perhaps
others more currently at the test tube may like to pour scorn or confirm.
Peter
Family Album/Gay Pride - http://www.dragonfire.net/~gallery/index.html
Also on Fixing Shadows: ----------- http://fermi.clas.virginia.edu/~ds8s
Future Press and elsewhere... E-Mail: petermarshall@cix.compulink.co.uk