The sour mash process is an old method of making whiskey. Many people credit James C. Crow with inventing the sour mash process, but the process is much older than James Crow. The Kentucky Historical Society has a recipe for sour mash whiskey from Catherine Carpenter of Casey County, Kentucky that dates to 1818. Her recipe is as follows:

“Out into the mash tub six bushels of very hot slop then put in one bushel of corn meal ground pretty course. Stir well then sprinkle a little meal over the mash. Let it stand 5 days, that is 3 full days betwist the day you mash and the day you cool off – on the fifth day put in 3 gallons of warm water then one gallon of rye meal and one gallon of malt. Work it well into the mash and stir 3 quarters of an hour then fill the tub half full of luke warm water. Stir it well and with a fine sieve or otherwise break all of the lumps fine then let stand for three hours then fill up the tub with luke warm water.”

Assuming she used a standard 48 gallon barrel as a mash tub, she would have used about 15% backset to sour her mash. This is what I have found to be a normal amount of backset in early sour mash whiskey. Many of the early distillers were doing a similar process in making their whiskey until James Crow came along and started making whiskey.

James C. Crow was an educated man and applied scientific methods to the distillation process. He kept track of temperature, specific gravity and the pH of the liquids at all steps of the process. He also tended to use a lot more backset in his process.

In the 1870s E.H. Taylor, Jr. hired a distiller who had trained under James Crow to make his whiskey at the OFC distillery. Taylor wrote in a letter that his whiskey was made by using the hot backset, as well as, hot water to cook his grains. This meant that he was using 50% or more backset in his mashing process. His distiller learned this method from Crow. Old Crow whiskey was considered the finest whiskey of the time and Taylor wanted his whiskey to be of the same caliber.

As the 19th century progressed people learned more about bacteria and yeast. With this growth in knowledge came a better understanding of the distilling process. This allowed distillers to adjust their own sour mash process in making their whiskey. Different yeast strains need different amounts of souring to create the favored environment and produce their flavors for the whiskey. Today they are using as little as 5% backset to as much as 40% or more backset. These different amounts of souring the mash do change the flavor profile of the beer and the final distillate.

In the 19th century there were some distillers making sweet mash whiskey, but the majority of the distillers made sour mash whiskey. The reason was simple – it gave a better quality control of the final product. The sour mash favors the yeast strain and helps inhibit bacteria growth that can cause a bad mash. The result was that by the time of Prohibition, sweet mash whiskey production was almost extinct. It would remain that way until the 21st century with modern equipment that could be kept cleaner and faster methods of testing the mash to give early warning if something was going wrong and steps could be made to correct the mash.

Today Sour Mash whiskey is the most common style of American whiskey. It is used in most Bourbon, rye and Tennessee whiskeys. It is an old process that has evolved over the years, but like distillation itself, it is still the same basic process as they were doing over two centuries ago.

Photos Courtesy of Maggie Kimberl