Art Table..."Cleaning"

The kids have an Art Table (low little desk area built in the kitchen). I loved the idea at first and really still do but it is a constant source of frustration because they don't clean it up.

So...I have started just collecting the stuff that is left out and putting in a box in the other room. They haven't figured it out yet and I'm wondering if/when they will start wondering where their supplies are or why things are getting sparse. I don't know if they will learn a lesson but it feels damn good to put the box under the edge of the counter, swipe it all into the box with little care, and end up with a clean flat space in the house!