Thanks for sharing this Jakobb.

Interesting though; IME, addition of gold chloride into the Ziatype (pop pd with Li2PdCl4) makes sensitizer more contrasty, giving relatively harsher tonal transitions - just the opposite of smooth. The color shift depends much on the moisture level in the paper during exposure, the lower is the RH the warmer will be the image, whereas the higher is the RH the colder will be the image. With Ziatype the smoothest results are obtained by using no additives or by adding small amounts of sodium tungstate only. (Which I don't like except for an occasional and very small addition that gives very mildly "yellow" highlights - only useful for a limited number of subjects IMHO...) Which paper was that? I haven't experienced this with Cot320, Weston and Masa papers myself...

Regards,
Loris.


Quote Originally Posted by jakobb View Post
I had problems achieving smooth mid tones and highlights with a lot of papers I tried recently (Buxton excluded). Gold(III) chloride (HAuCl4) is used to change the color and contrast in Ziatype printing. Dick Arentz mentions in his book that gold chloride can be added to the sensitizer (development process) and "this may also reduce granularity".
I added 5 to 10% of 5% HAuCl4 of the Pd Volume to the sensitizer. This resulted in very smooth highlights and mid tones. There was a small color shift to cooler colors. Using NH4Pd I got very neutral tones and with LiPd a slightly less warm tone. I have to do more tests with different developers, contrast control and papers (e.g. still problems with Revere) but I would prefer to add some gold to the sensitizer than extensive pretreatment of the paper to get good full scale.
Irving Penn was also using Iridium together with Pt/Pd and it may have a similar effect as gold as toner. I found no references for what compound he used. Ir(III) chloride? I found no solubility data through my web search. Has anyone used any Iridium salts? What color shift one should expect.