Figure out how to measure the air temperature inside the collector. You need to be able either to take the thermometer out of the collector and replace it without tearing a hole or to locate the thermometer in a place where you can read it easily. Line the inside surfaces of the collector. The sides of the collector should absorb as much sunlight as possible. Make sure you hold the heat inside the collector.
Cold air can enter the collector through holes, and warm air can escape through outside surfaces.
Point your collector so that it catches the Sun s rays. Try to catch as much sunshine as you can. You can print out this page and write your measurements in the table below. First, put your collector in a shady spot. Let it sit for 10 minutes so the temperature stabilizes.