Pasteurize water using the sun

What can we use instead of cardboard, aluminum foil, clear bottles, or a thermometer if those items are hard to find?

If you don't have cardboard use a flat metal baking tray or stiff poster board, replace aluminum foil with a clean shiny baking sheet or emergency blanket, use clear glass jars with screw lids instead of plastic bottles for step 4, and substitute a regular kitchen or meat thermometer for measuring the water temperature.

My bottles never reach 65°C—what should I check and change from the instructions to make pasteurization work?

Check that the foil is smooth and shiny (steps 3–4), that the panel and bottles face the sun directly and are away from shade (steps 1 and 6), ensure caps are tight (step 5), and improve heating by adding a flat black surface under the bottles or a second reflective panel to concentrate sunlight toward 65°C.

How can I adapt this activity for younger children or for older kids who want more challenge?

With preschoolers, have the adult choose the spot, prepare and tape the foil, and let the child place bottles and watch the timers (steps 1–4 and 8–10), while older kids can take thermometer readings themselves, adjust panel angle to reach 65°C, and record times and temperatures for comparison.

What are some ways to extend or personalize the pasteurize-with-sun activity after completing the basic steps?

You can decorate and label bottles, compare clear plastic versus glass jars (step 4), add a clear cover to create a greenhouse effect over the foil panel, build adjustable reflector wings (step 3) to focus more sunlight, and graph temperature versus time before sharing results on DIY.org.