Grand-Dad "high-rye" mash bill. Knob Creek: aged 9 years, 100 proof (50% ABV), with a 9-year, 120-proof (60% ABV) single-barrel expression, and a 100 proof (50% ABV) rye whiskey. Several of these offerings have performed quite well at international spirits ratings competitions. For example, Jim Beam's Black label was awarded a double gold medal at the 2009 San Francisco World Spirits Competition. Jim Beam Black also won a Gold Outstanding medal at the 2013 International Wine and Spirit Competition. Process Bourbon whiskey distillers must follow government standards for production. By law (), any "straight" bourbon must be: produced in the United States; made of a grain mix of at least 51% corn; distilled at no higher than 160 proof (80% ABV); free of any additives (except water to reduce proof for aging and bottling); aged in new, charred white oak barrels; entered into the aging barrels at no higher than 125 proof (62.5% ABV), aged for a minimum of 2 years, and bottled at no less than 80 proof (40% ABV). Jim Beam starts with water filtered naturally by the limestone shelf found in Central Kentucky. A strain of yeast used since the end of Prohibition is added to a tank with the grains to create what is known as "dona yeast", used later in the fermentation process. Hammermills grind the mix of corn, rye and barley malt to break it down for easier cooking. The mix is then moved into a large mash cooker where water and set back are added. The "set back" is a portion of the old mash from the previous distillation—the key step of the sour mash process, ensuring consistency from batch to batch. The distillery produces two different whiskeys based on two different mash bills, each used depending on the product line. From the cooker, the mash heads to the fermenter where it is cooled to and yeast is added again. The yeast is fed by the sugars in the mash, producing heat, carbon dioxide and alcohol. Called "distiller's beer" or "wash", the resulting liquid (after filtering to remove solids) looks, smells and tastes like (and essentially is) a form of beer. The wash is pumped into a column still where it is heated to over , causing the alcohol to turn to a vapor. The high wine at about 125 proof is moved to new charred American oak barrels, each of which hold