Beer style beer differently. Since sugars are converted to alcohol during the process of fermentation, gravity can be used to estimate the final alcohol. In beer brewing, a distinction is made between the "original gravity", the gravity of the wort before fermentation has begun, and the "final gravity" of the product when fermentation has completed. Since the concentration of sugars is directly proportional to the gravity, the original gravity gives a brewer an idea of the potential alcoholic strength of the final product. After fermentation, the differences between the final and original gravities indicates the amount of sugar converted into alcohol, allowing
Low-alcohol beer brews used at festivities. More recently, the temperance movements and the need to avoid alcohol while driving, operating machinery etc led to the development of non-intoxicating beers. In the United States, non-alcoholic brews were promoted during Prohibition, according to John Naleszkiewicz. In 1917, President Wilson proposed limiting the alcohol content of malt beverages to 2.75% to try to appease avid prohibitionists. In 1919, Congress approved the Volstead Act, which limited the alcohol content of all beverages to 0.5%. These very low alcohol beverages became known as tonics, and many breweries began brewing them in order to stay in business during