I bought some black Sumi ink and watercolor paper and got really into this. Like I had a dream about it. So I bought some colored inks and other paper options because the watercolor paper I first bought did not actually work well. Just heavy weight is not enough - it needs to be cotton for best ink absorption. The blue/yellow ink main photo is on Arches cotton paper & that one turned out the best out of many.
I experimented with Reiki and printer paper on this one. The Reiki caused the ink to begin to vibrate so I quickly picked it up with printer paper before it got too blurry and the effect was pretty cool.
This one used only a couple of drops of dish soap to 1/4 cup water and the dispersal effect was not quite enough. The ratio of dish soap to water affects things a lot. But I like how it kind of looks like a tree stump.
The original watercolor paper I got did not pick up ink well so I tried reusing the paper on another suminagashi. Layered effect is something I will experiment with more.
Paper tests - the paper from the printer at home works surprisingly well! Those are the ones with black.