Here is a link to my presentation at the APIS in Santa Fe, last October, which I mentioned earlier, above. Incidentally, I have refined the process considerably in the past 2 years. For maximum smoothness of tonality, and a rendered latitude of 11 stops or more, prepare ammonium ferric ferrous oxalate by adding just 3 or 4 drops of 1% ascorbic acid to 10 ml of 40% ammonium ferric oxalate. Only a small amount of ferric iron is converted to ferrous iron, but enough ferrous iron is there to obtain complete print out on totally dry paper. The contrast is quite low, grain extremely fine to invisible, and latitude quite wide. Mix the amm ferric ferrous oxalate with 10% gold at a ratio of 3:4. That is, for an 8x10, 9 drops of ammonium ferric ferrous oxalate with 12 drops of 10% gold chloride. You will likely have to add 1 drop of 26% ferric oxalate (no ascorbic acid) to every 3 drops of ammonium ferric ferrous oxalate. Therefore an 8x10 would need 4 drops 26% ferric oxalate, 9 drops ammonium ferric ferrous oxalate, 12 drops gold. For some negatives, you might even have to add 6 drops of 26% ferric oxalate! (Unfortunately, the dichromates won't do for boosting contrast with gold -- they grain it up. Only ferric oxalate works with no adverse impact on the image quality.) You will see ochre staining from the excess iron, but it clears out by the second bath. The first bath has to be a very weak solution of ice cold sodium sulfite. I do not say "has to be" lightly. Listen to what I explain in the video, and watch my other videos on youtube, especially the Karytype process video (printing out the formerly impossible combination of gold and platinum):
[video=youtube;MqGvy1ULXYc]http://www.youtube.com/watch?v=MqGvy1ULXYc[/video]