May 22, 2019

“Prove” It . . . by Joel Mann, Staff Wine Tasting Guy


We presently enjoy a well regulated consumer goods market where manufacturers are required to truthfully label the contents within the package. Producers are not allowed to make a claim that something contains X, when it in fact contains Y. That hasn’t always been the case.

Alcoholic spirits pose a challenge in distinguishing relative volumes of ethanol to water as both liquids are clear with a fairly neutral flavor profile that does not allow one to distinguish perceptible differences as concentrations of ethanol versus water increase or decrease. The flavor profile and physical properties of a spirit will change significantly over the concentration of ethanol to water however, so knowing the amounts of each is a valuable piece of information to possess if you manufacture spirits.

From the consumer perspective, since the financial exchange typically involves the amount of alcohol present in the spirit mixture, knowing the relative volumes of ethanol to water is also of concern. This month I want to explain the old concept of “proving” liquor, and give some detail on how physical properties change as the alcohol levels of the spirit increase or decrease.

The concept of alcohol proof dates back to the 18th century British Navy. Part of payment for service in the Navy throughout much of history was a daily beverage ration. Prior to 1655, that ration was in beer. In 1655, the English captured Jamaica from Spain, and the ration of beer was changed to a ration of rum, known as the tot. There was concern amongst the sailors that their rum ration would be intentionally watered down to extend the rum, and essentially stiff the crew of payment. The sailors devised a simple test to solve the problem. Gun powder ignites when sparked, however will not do so if wet. Gun powder soaked in alcohol that is high enough in ethanol volume will burn.

If the concentration of alcohol is too low, the powder fails to catch fire. If the concentration of alcohol is high, the flame burns yellow. If the concentration is just right, around the 57.15 % alcohol by volume range, the flame burns blue. If ever there was question about the watering down of the daily tot, a small amount would be mixed with powder and set on fire, “proving” its alcoholic concentration. The sweet spot to burn is given as 100 degrees proof, or 57.15% ABV. Degrees proof then has a 7/4 fractional multiplier by the volume concentration of alcohol (100% x 7/4 = 175° proof as an example).

This differs from the current concept of alcohol proof in America, which is simply the ABV times two.
Knowing alcohol concentrations matters, not just for proper rationing purposes, but because the physical properties of ethanol/water mixtures change as the concentrations of liquids in the mix change. The first issue to consider is that of volume itself. If you add 10 liters of ethanol to 10 liters of water, you don’t end up with 20 liters of product. The mixture undergoes a physical phenomenon called contracture, where the total volume is less than the sum of the two volumes.

For this reason, spirits blending is always done by weight, not by volume, as the weight of ethanol/water mixtures is always constant. The second issue in dealing with mixtures is that the aromatic properties change as the ratio of ethanol to water changes.
Most aromatic compounds that contribute the pleasant smells of a spirit have different solubilities in ethanol versus water. Higher ethanol concentrations typically result in more muted aromas, as aromatic compounds prefer to stay in solution with ethanol, versus being more volatile in water.

That’s the reason one often sees flavor ingredients, such as vanilla, prepared in alcohol solutions. Master blenders will often cut blending samples to half beverage strength in order to evaluate spirit stocks, as the higher water concentration makes for more aromatic character. That same reasoning should also make one willing to order a splash when buying a serving of liquor if you really want to smell its character. A final point to consider is the stability of mixtures. Certain liqueurs, such as absinthe, require higher alcohol concentrations as lower amounts result in breakdown of ingredients such as herbs, giving a hazy, dirty looking final product.

So the proof this case is in the fire. If you ever (crazily) think about trying this at home, just remember most spirits today are only 40% alcohol, and you’ll end up short on liquor with wet, useless powder. I recommend just enjoying the well-made beverage.

Drink responsibly.


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