Save that last slice of pizza! You can reheat it in its own container, using the sun's power.
Step 1: Draw a square Using the ruler and black marker, draw a square on your pizza-box lid, leaving a 1-inch border from the edge of the box to each side of the square.
Step 2: Form the flap With the box cutter or utility knife, cut through three sides of the square you just drew, leaving the line at the rear of the box attached. Fold the flap back so that it stands up when the pizza-box lid is closed.
Step 3: Cover the flap with foil Cover the underside of the flap with heavy-duty aluminum foil, which will reflect sunlight into the oven. Glue the foil to the flap, smooth out wrinkles, and cut off any excess.
Step 4: Tape plastic sheet With the scissors, cut two square pieces of clear plastic wrap, each 1 square inch larger than the flap opening. Open the pizza box, and tape one piece of plastic to the underside of the hole so that the plastic covers it.
Step 5: Tape second plastic sheet Close the lid, and tape the second plastic sheet over the top of the hole, creating a window that helps keep the sun’s heat in the box. Pull both sheets taut as you tape them.
TIP: Maintaining an airtight box is crucial in keeping the oven hot.
Step 6: Layer the bottom with foil Glue or tape a layer of aluminum foil to the inside bottom of your pizza box for insulation.
Step 7: Cover with black paper Cover the foil layer in the box with sheets of black construction paper and glue them into place. The black base will absorb light and generate more heat inside your oven.
Step 8: Find best angle Close the lid, and you’re ready to start cooking! On a bright day, place your solar oven outside in direct sunlight. Adjust the foil flap to find the best ray-reflecting angle, and use the ruler, a stick, or a hard-plastic straw to keep the flap propped in place.
TIP: If you want to test the reflective angles of your oven before you head outside, shine a laser pointer onto the foil flap to simulate rays of sunlight.
Step 9: Preheat Preheat your oven by leaving it in direct sunlight for 30 minutes. The box’s temperature will reach about 200 degrees, so while you won’t be able to cook a roast, you can reheat cooked food, melt cheese or chocolate, or—if you have all day—prepare a veggie stew.
Step 10: Cook Whatever you decide to cook, place it—on its own, or in a heat-safe container—in the center of the oven, so that it is directly under the plastic-wrap window. Close the lid, leaving the flap propped open, and check on your food every 15 to 30 minutes.
FACT: Earth receives more energy from the sun in one hour than our entire planet uses in a year.