circle stamping

I've been quite environmentally conscious recently. Recycling my trash at the recycling bin. Reducing the amount of food I buy. And Reusing some of my trash too! I'm sure everyone is always frustrated with the bottles, bottle caps, toilet rolls and paper towel rolls, foil rolls, etc, accumulated! Somehow using them for Nat's painting fun before recycling all of them makes me less guilty about trash! :P Great way to start simple motor skills in stamping. Somehow kids really like circular stuff before they like other shapes. Does anyone know the reason behind it? Stamp away those circles!