Okay, I was doing some checking on the internet about some more info on 4 color gum printing when i came across an article which had some info on multi layer Pt/Pl printing. All I could get out of it was, that doing at least 3 layers gives you much better deep tones and your black are a lot more rich. from there I can not find anyone doing it or any articles on the layers of negatives used. Are they like the 4 color gum with different separation negatives exposing for different tones on the final print or are you using the same negative. I understand the registration thing. I do it all the time.