Looks like Mike is way ahead of the rest of us (not at all surprising). I know a little about inkjets. I would think that a cheap HP would be the way to go as their heads are integrated into the cartridges and are disposable. They use a technology that heats up the ink locally and it squirts out from the pressure of "boiling" the ink. Epson uses a piezo element to do the squirting. Not sure which technology is easier on the ink/chemistry. I would expect that you may also have to add some sort of surfactant to get it to go through the inkjet head nicely (could be wrong). A little Tween 20 might help. Too much tween will make it spread in the paper too much though.