When World War II brought rice shortages, the sake-brewing industry was hampered as the government discouraged the use of rice for brewing. As early as the late 17th century, it had been discovered that small amounts of alcohol could be added to sake before pressing to extract aromas and flavors from the rice solids. During the war, pure alcohol and glucose were added to small quantities of rice mash, increasing the yield by as much as four times. 75% of today's sake is made using this technique. There were a few breweries producing "sake" that contained no rice at all. The quality of sake during this time varied greatly.