Hydroponics is a method of growing plants without the use of soil. Instead of getting nutrition from the soil, plants get their food from a nutrient solution mixed with a reservoir. Plants either hang into the nutrient solution or are planted into a growing medium such as perlite. It's easy to make a simple hydroponic system that does not run on electricity.
Cut your soda bottle just below where the bottle stops curving at the top.
Poke a hole through the bottle cap, using a pencil or other sharp object.
Feed your yarn up through the bottle cap. The yarn should be about 16 inches long.
Fill the top of the soda bottle with perlite, winding your wick through the material as you pour. The wick should go through the material in a spiral.
Fill the lower half of your soda bottle with a mixture of nutrient solution and water, according to the instructions on the nutrient solution bottle and what kind of plant you are adding to the perlite.
Place the inverted soda bottle top onto the bottom half, allowing the wick to touch the nutrient solution. Place your plant into the perlite and slightly wet the potting media with a small bit of nutrient solution. As the plant needs nutrients, it will draw the solution up through the wick.