RE: Pure Pt printing and solarazation

Cor,
How did you make your platinum salt? If it was made by reduction of the
Pt(IV) salt it is possible that you might have some unreduced platinum left
in the solution. It would act as a contrast booster, similar to Na2PtCL6
method used to adjust palladium print contrast. Longer exposure time would
be consistent I think. I have not printed pure Pt, so I am not sure how it
behaves.
Marek

>From: "Breukel, C. (HKG)" <C.Breukel@lumc.nl>
>Reply-To: alt-photo-process-l@sask.usask.ca
>To: "Alt-Photo-Process-L (E-mail)" <alt-photo-process-l@sask.usask.ca>
>Subject: Pure Pt printing and solarazation
>Date: Thu, 01 Dec 2005 10:09:45 +0100
>
>Hi,
>
>I recently entered the world of pure Pt printing..(caveat: I "made" my own
>K2PtCl4, which is AFAIK quite pure, but I am not 100% sure about it, do not
>have the means to test for impurities)..and as expected: it isn't a easy
>world..;-)..
>
>I have tried a few things: Pt & FerricOxalte, Pot.Oxalate as developer, and
>Extravagatype: Pt & AmmoniumFerricOxalate, developed in 1:1
>glycerol/PotOxalate with a foambrush, both were dried "bone dry" with a
>hairdrier at medium heat (RH in my place around 70%, temp 16degC).
>
>Paper: Simili Japon
>Chemistry: 200 ul K2PtCl4 (say around 4 drops)
> 200 ul 25% FerricOxalate
>Negative: 4*5, processed in PyrocatHD
> Stouffer Stepwedge
>
>I observe the following with both approaches:
>
>long printing times: about 1-1.5 stops longer compaired with a Ziatype
>(both with a Stouffer stepwedge and a 4*5 neg), which means printing times
>in the range of 25-35 min! (versus a Zia around 9-11 minutes) with my set
>up.
>
>Reversal/solarization of the deepest blacks & border : they turn in a
>ligther brown versus a a deep brown/black in the detailed shadow area.
>
>Overal image tone is black brown, the Extravagatype beeing a deeper black.
>
>I can think of the following things to explain the solarization: Stiil too
>humid? Too little metal? (I can not load more in one coat, this amount is
>already on the edge, the metal solution seems to be at it's saturation
>point, at room temperature it's ok, at 16deC (my darkroom in winter time)
>there are nice red crystals precipitated). Too long a printing time? Don't
>know what to do about that (btw I cool my UV bank with fans).
>
>I also tried some Ziatyp with Pt: I used 30 ul Pt, 90 ul Cs2PdCl4 and 120
>ul AFO, dried very quick, printed very humid (with a piece of saran wraap
>to protect the negative. I obtained a nice print, neutral grey of tone,
>nice midtone separation, a bit lower Dmax compaired with the Pt print.
>
>But the most striking (but not surprising) thing was the hughe difference
>in tonal values. The pure Pt print has almost blocked up shadows, and could
>use some more density in the highlights, wheras the Ziatype had very open
>shadows, good density in the midtones, and a tad to heavy in the
>highlights. I guess this demonstrates the effect of self masking in POP
>quite nicely. To repeat: I used the same neg for both prints: for the pure
>Pt this neg is too heavy (too much contrast in the print), whereas for the
>Ziatype the neg could use some more density (although this is easily
>"cured" by adding a litle bit of amm. dichromate).
>
>Comments and advice appreciated!
>
>Best,
>
>Cor
>
Received on Thu Dec 1 08:24:28 2005