Step 2: Plan a fair test of your design. You'll build a model pile (sand + dyed salt) and "make it rain".
Change: the cover/barrier. Observe: how much colour washes out. Keep the same: the pile, the water, the way you pour.
Presentation page 3
Step 2: Plan a fair test of your design. You'll build a model pile (sand + dyed salt) and "make it rain".
Change: the cover/barrier. Observe: how much colour washes out. Keep the same: the pile, the water, the way you pour.