Beer anh ale are beverages, produced by fermentation, each having a characteristic flavor and aroma. They must contain not less than 1/2 of 1% of alcohol. Their alcoholic content generally ranges between 3 and 6% by volume. A gallon of beer or ale weighs 81/4 lbs. Beer and ale are similar, but beer is produced by bottom fermentation/ although this procedure is not always used/, and ale by top fermentation. The type of yeast used, the temperature of fermentation, and, in rare cases, bacterial action, all influence the characteristics of the brew.