When I started making collagraphs, I initially worked only in monochrome. But after about six months, I got a bit bored with Prussian Blue...
I decided to learn how to combine intaglio inking with surface rolls. In this process, you ink and wipe the plate with a fairly dense ink, usually in a darker colour, and then roll over a looser, more transparent ink with a single pass of a roller. Because of the difference in viscosity, the intaglio ink will repel the ink from the roller.
Here's a short video of the process:
I have been experimenting with this method for a while now, and this is what I've learnt so far:
There's no point trying to save money by buying a small, cheap roller, as it's almost impossible to cover the whole plate in one pass with one of those. You just end up spending more money on ink and paper, because the failure rate is so high. I eventually bought a soft "mini spindle roller" from Hawthorn, which is anything but "mini"! It's a whopping big beast, and works beautifully.
You can't use Linseed Reducing Jelly to loosen the ink you use for the relief roll - it needs to be oil.
There's a lot more cleaning up to do!
In my "Foxgloves" print, the darks were created by cutting into the mountboard and peeling away the top layer. These areas have retained the blue intaglio ink, and repelled the pink ink from the roller.
The sky and the highlights on the foxgloves were created with PVA glue. When I wiped the plate, most of the blue ink was wiped off these areas, so they readily accepted the pink ink from the roller.
I think most interesting areas are those where the two inks have mixed, like the leaves, and the lower part of the sky.