Pure Pt printing and solarazation

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 03:10:35 2005