Lighting Up With a Coke Bottle and Water

These "lights" were first used in the Philippines, where people discovered that when sunlight hits the top of a plastic bottle filled with water the light diffuses in a way that it acts like the equivalent of a 55 watt bulb. This is free, heat-free, electricity-free light.

By Rodger Harrison
Imagine lighting your home for free using nothing more then a coke bottle filled with water. Sounds incredible doesn't it? This is one of those discoveries where you find yourself saying, "why didn't I think of that?" After 14 years of living in a Third World country and often visiting mountain homes, I have seen first hand how dark a mud hut with no electricity can be even in the middle of the day. Candles and flashlights are both too expensive for most people without electricity, so I was amazed to learn this simple trick to make light. In this way, the poorest people in the world can have light with nothing more then a plastic coke bottle, some water, and a few hand tools. It's virtually free.

The system is so simple that it will make you laugh. These "lights" were first used in the Philippines, where people discovered that when sunlight hits the top of a plastic bottle filled with water the light diffuses in a way that it acts like the equivalent of a 55 watt bulb. This is free, heat-free, electricity-free light. That's bright! As long as the sun is shining, you have free light in your house. The stronger the sunlight, the more light comes into the house. And at night you don't have to worry about turning off the lights.

All you need is an empty plastic bottle with cap, water, a little bleach, a tool to make a hole in the roof, and some type of sealer. Oh yes, I almost forgot you will need a ladder too.

Step 1
Get your ladder and go to the top of the roof and get one of the clay shingles down from the top and then cut a hole using a small chisel and hammer. We use a small drill to make a series of holes and then gently punch out the hole.

You can use the big two liter bottles as well. The bigger the bottle, the more light. Since we often work with ceramic roof tiles that are narrow, we find that using the smaller bottles works best.

Step 2
After you have made your hole, test to be sure that the bottle will fit -- the top of the bottle sticks out of the top of the roof and the bottom of the bottle hangs down inside the house like a big fat light bulb.

Step 3
Next you seal the area around your bottle. There are different ways to caulk and make the union water proof. Regular sealant like you might use on a boat or bathroom will work. Once the hole is sealed check to make sure that it does not leak. Also if you like you can fill the bottle with water and add a teaspoon of Clorox before sealing the bottle. Now your light is ready to install. At this point you climb your ladder and replace the roof tile and put it back where it was. (The bleach is too kill the germs and algae that are in the water so your light source does not go green as time passes.)

Step 4: Final Product
We used our own storage room for this test. Before the lights were put in place the room was almost totally dark. To make the test even better we have covered the one window with black plastic, and this picture was taken with the door closed as well so all the light you are seeing here is the natural light coming from five 16 ounce plastic coke bottles. Total cost for this project was US$1.30 for the tube of sealant. The bottles came from the trash and the roof tiles were taken from the existing roof and modified. Now that is what I call cheap lighting. (11/18/11)

Note: The author lives in the town of Copán Ruinas. He is the founder and president of Paramedics For Children, providing educational and healthcare services to the people of Honduras since 1997.