I became interested in this process after seeing Dan Burkholders work and that of Ron Reeder.
Rene
Hello Gang-- I just found this thread. And since I used to do a lot of digital color/palladium work, I will offer my biased opinions (my approach is written up on my website
www.ronreeder.com but it is based on a Photoshop/printer version that is rather outdated by now).
Personally I expect that any printer that uses the Ultrachrome inks (either K2 or K3) will work fine. By the time you get all the layers and go through the processing baths any fine distinction between print heads will probably be lost. I used Arches Platine and a 2200 and had no complaints. Far as I know, the only essential characteristic of the ink is that is must be able to stand all the processing baths (if you put the color down first).
My approach was to hand color a black and white image in Photoshop (in RGB mode), then change it to CMYK with maximum black separation. The K channel was inverted and used for the pt/pd neg (with appropriate correction curves, of course). The CMY channels were then combined and changed back into RGB mode before printing them onto a sheet of paper. This whole approach is gloriously uncontrolled when it comes to color. The CMY channels are a bit dull and they get rather neon when switched back into RGB. However, this compensates for the fact that I had no profile at all for Arches Platine and printing the color on that paper dulled them back down again. When combined with the pt/pd layer everything miraculously came together and looked pretty good (whew!)
If you lay down the color first, then print the pt/pd over that there are plusses and minuses. On the plus side it is easier to register if you put the color down first (take the time to use the pencil tool in Photoshop and place small black corners on the color layer to provide registration marks for the pt/pd neg that will come next). A minus side of putting the color down firstthe Epson inks tend to act as wicks and suck the pt/pd chemicals down into the paper such that it is nearly impossible to clear them out of the final print. Some batches of Platine are sized so that this is a real problem, others do not seem to have a problem.
If you print the pt/pd first, then you will have a problem getting the color layer to register properly since it will depend upon being able to feed the paper reproducibly though the printer. If I went this route I would first run a sheet of paper through the printer and print just the corner registration marks. Use these to align the pt/pd neg. Then process, dry, and run the paper through the printer again to put down the color. This approach gives you half a chance. HOWEVER, most of the sharpness comes from the pt/pd and the color often can be fuzzed out a bit and still look pretty good.
Frankly, these days I tend to agree with Loris and prefer the look of color put down as multiple layers of gum. Much more laborious, but you get a softer, more funky hand built look which I like.
Cheers, Ron Reeder (ron-san)