Eventually, inevitably, the children began doing their own refills of liquid water colors (I used red and white in the tune of Valentine's Day) and fetching pitchers of water from the bathroom.
We had to intervene (only because we were inside) when they began pouring the glumpy solution straight onto the cleaning rags. I think they got the fullest possible experience from this activity.
It all ended up in one glorious pitcher of pink mush. The children would only allow us to clean up this activity with the promise of getting to do it again (that will be tomorrow, haha).
(I double-dog-dare you to challenge me as to how this open-ended, play-based, child-led activity is beneficial to children's development!!!)