Putting ballpoint pen ink on the tip of a leaf then putting it on water (or milk if you want it to stand out) causes the leave to whizz around leaving trail of ink behind.
He then sought to find out why this happened by combining different ingredients. Sadly, it didn’t give him any more information, but he seemed to have fun with it nonetheless.
I have played around with different combinations of ingredients. For example, here is the dye with phenoxyethanol and oleic acid. And here’s the dye mixed with phenoxyethanol, oleic acid and a surfactant. I tried these different ingredients in different concentrations. I didn’t get anything much different than what I’ve shown you already. So there’s still a mystery here.
via Nag on the Lake