Why is this whiskey called bourbon? It takes its name from Bourbon County, located in the central Bluegrass region of Kentucky. It was formed from Fayette county in 1785 while still a part of Virginia and named to honor the French Royal Family and was once the major transshipment site for distilled spirits heading down the Ohio and Mississippi rivers to New Orleans. Barrels shipped from its ports were stamped with the county's name, and Bourbon and whiskey soon became synonymous. Webster's New Twentieth Century Dictionary, Unabridged, 2cd ed., s.v. "proof" and "proof spirit." Proof, 8. The relative strength of an alcoholic liquor with reference to the arbitrary standard for proof spirit, taken as 100 proof. Proof spirit, An alcoholic liquor, or a mixture of alcohol and water, containing 50 per cent of its volume of alcohol having a specific gravity of .7939 at 60Â° F. Before the hydrometer became a common instrument of the distiller there existed a method of proofing known as "gunpowder proof". It was a simple procedure and took advantage of readily available "tools". Bourbon and gunpowder were mixed in equal proportions in a small fireproof vessel and ignited. If the flame burned yellow the liquor was too strong, if it burned blue the proof was true. A yellow proofed liquor was mellowed with spring water until it burned blue. The proof of a blue flame spirit was about 100, or 50 per cent. You may use the calculator below to answer the question "To dilute bourbon of proof x in order to achieve proof y, how much water must I add?" Note that the calculator is non-dimensional --that is -- the value returned by the calculator will be in terms of the units used. Ounces can be used as easily as ml, liters, gallons, or what have you. For example, in order to reduce 750 milliliters of 142.7 proof bourbon to 90 proof, you would need to dilute the original volume with 439.16 milliliters of water. There are strict laws governing just what a Bourbon must be to be labeled as such. For example, at least 51 percent of the grain used in making the whiskey must be corn (most distillers use 65 to 75 percent corn). Bourbon must be aged for a minimum of two years in new, white oak barrels that have been charred. Nothing can be added at bottling to enhance flavor, add sweetness or alter color.