Clean the ginger and cut into small chunks. Grate the ginger, or use a food processor to mince using a little of the water. Put grated ginger and water into a large glass jar and cover loosely. Store in a cool place for at least 24 (to 48) hours. Strain carefully and sweeten. Brown sugar gives it a dark colour. White sugar will give you a lighter coloured beer. Bottle and refrigerate. If there is further sedimentation, pour off the ginger beer carefully. Serve over crushed ice.