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Platinum prints
The platinotype and palladiotype are iron-based processes in which the photosensitive ion is an oxalato-complex of iron(III).
One of the important points in all the iron oxalate methods is the concentration of the iron metal ions in
the paper sensitizing solution used. For the iron oxalate solution it is now days suggested that the solution is prepared
from ammonium-iron(III)oxalate (available from Riedel-deHaën AG. D-3016 Seelze 1).
I have found out, by a lot of testing, that
a nearly saturated solution can be made by desolving 30 g ammonium-iron(III)oxalate in 50 ml of water.
The aqueous sensitizer solution consists of a mixture of equal volumes of that ammonium-iron(III)oxalate solution and
the platinum(II)chloride- or palladium(II)chloride-solution. The later can be made up by desolving 5 gram of
ammoniumtetrachloroplatinate(II) or ammoniumtetrachloropalladate(II) in 30 ml of water.
The contact printing under UV light is almost direct and depending on the humidity. In a normal house with a 50-80 % relative humidity,
the image can be seen close to ready without any development, but this should be finalized in water with about 7 wt-%
ethylene-diamine-tetra-acetate (EDTA) as a complesx agent to remove excess iron-ions.
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