Originally Posted by Jorge
If you use Fabriano Artistico Extra White HP for gum over platinum, you should not have any registration problems. The oxalic acid presoak before the platinum layer (if this is a PITA, maybe you should take up digital printing - KIDDING!) will give a bit of a pre-shrink. The other 2 key steps for getting good registration are:
1) Make sure you dry your platinum-coated paper very well before you expose it. This way, the paper will be as small as possible before you make the platinum print. You may not get quite as rich a platinum print as you would with a little moisture in the paper, but the subsequent gum coat(s) will more than make up for it.
2) Don't use very hot potassium oxalate when you develop the platinum layer. I usually use it at ~80 degr. F (although I use it MUCH hotter if I'm not doing gum over). You won't get as warm a print, but again, the gum layer(s) will be in control of your final print color, not the platinum layer.
(BTW, I also have yet to see a platinum over gum print that is even in the same league with gum over platinums.)
It's all really pretty quick and easy once you get a rhythm going, and the prints are SO MUCH nicer than straight pt/pd, how can you NOT do it?