Pure Pt printing and solarization..follow up and preliminary conclusions

Hi,

About 2 weeks ago I posted some results on my "home-brewn" Pt mixture which appeared to solarize easily, printed high contrast (later experiments indicated that the solution was only suitable for "normal" silver gelatine negatives).

Marek suggested that there was perhaps contamination of K2PtCl6 (Pt(IV)) in my K2PtCl4 (Pt(II)) preparation, and this Pt(IV) could work as a contrast agent (as Na2PtCl6 aka Na2 does). K2PtCl6 is only slightly soluble (Handbook of Chemistry and Physics: at 2degC about 0.5 gr and at 100degC about 5.2 gr in 100 ml water, no data for roomtemp.)

Since I made my K2PtCl4 by reducing K2PtCl6 (not to completion to avoid reducing to Pt), K2PtCl6 could be present. The obvious step was to try reducinga sample further. This time some fine black powder precipitated (Pt), so the reduction of K2PtCl6 was assumed to be complete.

This K2PtCl4 printed as expected and gave nice prints, although it still has difficulties with an overexposed PyrocatHD negative (a very slight solarisation and excessive printing times of 40 minutes). The same negative prints in about 15 min. as a Ziatype in my set-up.

Hope this is of some interest,

Best,

Cor
Received on Mon Dec 12 23:44:39 2005