Denaturing and “Renaturing” Industrial Alcohol
The addition of chemicals to industrial alcohol stocks to denature them made them exempt from the liquor taxes imposed on drinkable alcohol. As a result, industrial alcohol manufacturers were more than happy to comply with the government directive to denature their stocks. People determined to remove chemical additives from denatured industrial alcohol could do so if they really wanted to. Some did just that, with a process known as “renaturing”. However, with legal alcohol readily available, and often quite cheap, there was little incentive to go through the trouble.
That changed with the enactment of Prohibition, and the resultant scarcity of regular drinkable booze. Liquor did not disappear from America because of Prohibition: massive amounts of drinkable booze were smuggled into the country by bootleggers. However, Prohibition disrupted the supply chain, and even smuggling on a massive scale was not enough to meet the demand. So bootleggers began to produce massive amounts of liquor in the United States. They sourced it from stolen or otherwise diverted stocks of industrial alcohol.