Large piece of organic ginger root with the skin on
Grate 2 tbsp of ginger and mix with 2 tbsp sugar in a quart jar. Add 2 cups of water. Stir very well to aerate the mixture. Cover with muslin cloth or a coffee filter and secure with a rubber band. Store in a warm place, out of direct sunlight.
Each day, at roughly the same time, feed your ginger bug with 1 tbsp of sugar and 1 tbsp of grated ginger, stirring to combine.
If the culture is active, bubbles will form around the top of the mixture, it "fizzes" when stirred and it has a sweet and mildly yeasty smell. It will also become somewhat cloudy and opaque. If the mixture hasn't taken on these characteristics by the 7th or 8th day, you will need to discard it and start again. If mold appears on the top, spoon it off. If this happens more than once, you will need to start again.
Once the ginger bug has cultured, it can be used to create fermented sodas, such as Cultured Ginger Beer.
Continue to feed the ginger bug daily to maintain its strength. You can also "rest" the ginger bug in the fridge, feeding it 1 tbsp each of ginger and sugar once a week. To reactivate it, remove from the fridge, let it reach room temperature and begin feeding it again daily.