Step 1Place a light socket, with a cord attached, upside down on top of a Styrofoam cooler lid. The larger the Styrofoam cooler the better. Trace a circle around the light socket and use a utility knife to cut out the hole.
Step 2Place the light socket into the hole, widening the hole with the utility knife if needed. Let the cord run out the top. Make sure you can reach the on/off switch from the outside. Add a dimmer switch to the cord. This allows you to control the temperature from the outside of the incubator. Make sure the dimmer switch is for table lamps and not a light switch installed on the wall.
Step 3Take an 8 x 11 piece of glass, found in picture frames, and cut out a square slightly smaller than the piece of glass into the side of the cooler.
Step 4Use tape or wood glue to attach the 8 x 11 piece of glass onto the side of the incubator. Glue it to the outside, not the inside. This creates a sealed window to view the inside of the incubator through.
Step 5Punch a few small holes in the side of the incubator. They provide ventilation. Consider buying a small, plastic fan and placing it in the back corner of the incubator to help circulate the air. You'll need to run the cord out the side like you did the light socket cord. If you cannot find one that will fit, continue without it.
Step 6Fill a small bowl with water and place it inside the incubator. This helps with humidity.
Step 7Place a thermometer in a clear plastic sleeve inside the incubator in a location you can see clearly through the window in front. The base should be at the same height as the eggs will be when you place them inside.
Step 8Put a 25 watt light bulb into the light socket, or a 15 watt light bulb if your incubator is made from a small Styrofoam cooler instead of a large one. Close the lid and plug the light bulb in.
Step 9Turn on the light bulb and the fan, if you included one. Allow them to run for several hours and monitor the temperature. Tape over ventilation holes if the temperature remains too low, and poke more holes if it stays too high. You can also adjust the strength of the light bulb using the dimmer switch to control temperature.
Step 10Place the eggs inside the incubator after you feel you can keep the temperature within the desired range. Make adjustments to the ventilation holes, the strength of the light bulb or the fan to help get the temperature to the right level and keep it steady before beginning.