Here is a LL link to one of the discussions with Angel, the Spanish guy who was a consultant to HP who engineered the workflow for high-end digital negs on the Z3200 printer. We emailed back and forth about 5 years ago and he told me at that time that Hp had lost interest in dealing with such things because it didn't reward them with a quick profit market. So, they made him take all the great work he had done off of their website.
As a result all of the links that went to those HP websites are now not available to us.
We may be able to find a way to contact Angel. But he has to be careful because this work was the property of HP, and even though they don't care about encouraging it, they sponsored it.
He sent me a curve that was designed for the 3200 to analyze and now when I need it I can't find it. But essentially it was some form of greenish gray, as that hue worked best in rendering the best subtle tonal range under printing with uv light.
http://forum.luminous-landscape.com/index.php?topic=45662.0Angel had other posts about this on other forums that are linked to in this LL post.
I hope we can all share info about this use of the Z for platinum negs as we experiment. Because Angel did so much work on this it would be to out advantage to re-read what he has written about his findings. For the Z3200 users it was all worked out and he had curves for various processes, so it was just a push button method, quite unlike Nelson's Precision Digital Negs that requires a lot of tests and spectro readings off of the analogue prints.
I know from seeing some of Mark Nelson's greenish yellow negatives for platinum that they were on the same track, only with different printer makes. It is my understanding with Nelson's method you can use any modern color printer to make them.
Cone's method that is really excellent is all worked out for you with curves for various processes, and it uses gray and black inks only. I want to try them all.
john