There are several methods for making multiple-color relief prints, and in every case, the tricky part is the registration of the colors. In a reduction print, the same block is used throughout. You print a number of copies of the first color, then carve away a bit more, print another color, and so forth. By the end, of course, the block cannot be used to print another edition because most of it has been carved away. But the registration issues only involve placing the paper in exactly the same place every time.
When printing from multiple blocks, both the paper and the different blocks have to be in register for every copy. But nothing is destroyed in the process; you can print editions with different colorways, start over, add additional colors by making another block. I've made a few two-color prints, but this was the first time I tried three. Above are proof prints of each of the colors that will be combined onto one sheet of paper in the final print. Below, the blocks used to create them.
One block, called the key block, contains the most helpful information for keeping everything in one place - in this case, that's the black one, with the most complex detail. The other blocks are based on it and have to be created in perfect register. This is not particularly easy, because of the amount of handwork involved in tracing a mirror image onto a substrate that's going to be carved by hand.The blocks have to be exactly the same size, and held by some sort of system - I used a jig that I made out of matboard, mounted securely on a slightly sticky mat of a vinyl material used to line shelves. There also has to be a method for placing the paper in the same place for each color impression: I used finely-ruled lines on the edges of the matboard; for a larger print I would use a pin-registration system similar to that used by offset printers in the days before digital pre-press.
Below, the blue block and red block have been printed. The black lines of the key block will cover the gaps that you can see in the image, for example around the upper hand, and the triangular motif of the gown below the neck. (For the final edition, I mixed a slate-blue color rather than the brighter blue shown here.)
I'm just learning about the technical problems involved, but I have to admit, it's the kind of challenge I like - and it fits pretty well with my early days as a graphic designer, when we cut masks out of rubylith and had to figure out the registration of multiple-color jobs ourselves, setting them up manually. And it's OK with me not to have an absolutely perfect result - part of the unique beauty of a hand-pulled print is that it is just that: handmade. We're so used to computers making everything perfect. This is an ancient process, and I like it for exactly that reason.