Mike, THe only other published source that I know about, is that bad scientist Jeffrey Mathias ; ) .. Some years back when Dick started pushing his POP known as the Ziatype, several of us on the alt photo group tried his new beast. While I only used components of the Zia system and never practiced its less scientific approach to humidifying paper, I can do some math.
Originally Posted by photomc
If the intent is to make Li2PdCl4, then one uses 2 LiCl and 1 PdCl2; that is the way it works. LiCl has a formula weight of 42.39 and PdCl2 is 177.31. Doing the math, I just could never come close to what Dick recommends by 1.7 with 2.3. The ONLY justification I can see to use that much LiCl is that is hydrosopic or deliquisant (sp); it has the ability to pull H2O out of the air. I have seen this in my darkrooms. In Taos, when I first tried it the RH is very low. I didn't concern myself with little bags of silicate to absorb moisture, but here in Dallas it is another thing all together.
If you are trying to make sure that you have enough LiCl in solution, it would be better not to short change that weight. It may be that Dick is simply making sure that there is adequate ions in play. I forgot his reasoning, but there was some discussion of that in and around 1995 +/- a few years. I have ONLY tried it my way the way the math supports it. I was thinking about this last night after I posted the formula. I suppose you could dry it out carefully to drive away the water and weigh your salt then. I bought my LiCl from Artcraft. I don't make prints with it as the sole source for palladium but rather as a cooling agent and contrast reducer.
My sodium mix is 3.5 with 5 grams and ammonium base is 3.1 to 5. 3.3 would be more mathematically correct with sodium butI rarely use pure sodium chloride, so once again I error on the side of more than adequate. I had used a sheet that Tom Millea made up in the late 70's and he had mistakenly put nearly twice the amount of sodium chloride in the formula. His was the only text that I had so that was the way I mixed it. Years later I saw the correct information and it all made sense. I eliminated the excessive amount of sodium and the print speed increased as did the contrast.
I have not had any problems with my Lithium based palladium solution acting funny or unexpected compared to my sodium or ammonium based solutions.
I did make some pure Li prints early on just to test it. And when I use larger amounts of Lithium solutions, 25 to 50 % of the metal portion, I generally do not humidify for as long. It seems to still retain its thirst for water while in the coating.
hope that helps