For the teacher to use in the introduction:

• waxy-leaved plants, such as kale, cabbage or broccoli
• water
• soap (hand or dish)

Each group needs:

• 5 mL (1 tsp) oil (vegetable or olive)
• 250 mL (8.5 fl oz) of water
• 1 paper clip (or some large-ground peppercorns, which are easier to use with better reproducibility)
• 1 clear 12 fl oz (355 mL) cup
• soap (hand or dish)