We can look for certain things with good faith on our favorite bottles of spirits. Front and center, bold, sometimes brash, brand names hug the curvature of the glass. Details of manufacture boast of select ingredients and refined processes. The bottle itself curves and entices with blown details. Then, on a corner in small print a number followed by “ABV”.
The ABV (alcohol by volume) is a legal requirement for all alcoholic beverage labels. Consumers have a right to know what they’re getting themselves into when they purchase a bottle. It is optional, but permissible, to include a proof measurement as well. In the United States, proof is exactly double alcohol by volume. But why do we use a redundant measurement such as proof? More importantly, how do we measure alcohol by volume in the first place?
We can measure the strength of our booze using either alcohol by volume or proof. Both of these measurements describe how much ethanol is in a drink as a percentage of the total liquid volume. Alcohol by volume spans a normal 100 percentage points with typical beers measuring from 4-7%, wines from 11-13%, and liqueurs and spirits from 28-50%. Proof is simply double this number and, in that specific proportionality, is used only in the United States.
The term proof has British origins dating back to the 1500s when alcohol was tested for tax purposes. Strong spirits were levied with an excise tax. To decide which spirits were taxed as strong, the tax man performed a sort of experiment. Booze was poured on a bullet and if it still ignited, then that was proof of the strength of the alcohol. This threshold would mean your spirit was somewhere around 50% alcohol by volume. This established a specific ratio that the term proof represented in England, but it has been used to mean double the alcohol by volume in America since the 1800s.
We might know how strong our drinks are when we buy them at the liquor store, but how do we measure the strength of alcoholic beverages at home? If you make your own booze, there are several methods that can be used to estimate and accurately measure just how much alcohol there is in a liquid.
First of all, if you know how much sugar is being added to a fermentation, you can calculate how much alcohol could theoretically be produced by yeast. If yeast have not died off due to the strength of the alcohol, all sugar should be converted to alcohol. Generally, 1 pound of sugar in 1 gallon of water can yield 6% alcohol by volume. Beer brewers are familiar with a version of this method as they measure the density of their brews before and after fermentation and deduce from these measurements how much sugar has been metabolized into alcohol.
An alcometer is exactly what it sounds like—an alcohol meter. It is a kind of hydrometer specifically gauged for ethanol. It looks just like a thermometer and measures alcohol using buoyancy. The alcometer is suspended in alcohol and floats according to the concentration of alcohol in the liquid. Alcohol is less dense than water, so as the percent alcohol increases, the liquids density decreases. As it decreases, the alcometer sinks more and more. The tool is calibrated in such a way that the meniscus of the booze will show the proof or ABV of the liquor. This method of measuring is really only suitable for unadulterated, strong spirits. The presence of sugar in the liquid will distort the measurement. Temperature, too, will influence how the tool measures density.
When testing strong spirits, you can simply shake a glass jar and watch the bubbles. This is the manner of proofing most popular for those without scientific instruments. It can be casually referred to as the shake test. When you shake your booze, you are looking for two things: the size of bubbles, and the duration of bubbles. Big bubbles that are quick to disappear are a sign of high-proof spirits. Lots of small bubbles that stick around indicate that your booze is relatively weak. Because alcohol is less dense, it allows for air to consolidate into larger bubbles and releases them quickly. The higher density of water forces air into smaller pockets but also allows them to remain in the liquid. This method requires practice. There is no sure-fire way to shake and say this is 57% ABV, but a practiced distiller can get a knack for naming proof within a couple degrees of the actual ABV.
It is, after all, important to measure how much alcohol is in a drink. Whether you’re drinking a 4% mass-market beer or a 10% imperial IPA makes a big difference when you might be driving home afterwards. It is worthwhile to know not only what the percentage means on the side of a bottle but also how it was measured in the first place. Remember, proof originally came from strong spirits—so the most rudimentary test is to hold a match to your booze. If it ignites, that’s proof enough you have some strong stuff.
Imagine if New York City didn’t have clean tap water. Those folks selling bottled water on the street corner would make a killing.
Tapé is an Indonesian delicacy that can be made from rice or cassava. The starchy foods are fermented into a sweet paste that can have an alcoholic content of up to 8% by volume. These boozy snacks are made traditionally, using fermentation starters called ragi which carry mold and yeast.
Originally, the city opted for creek water to avoid the Monongahela, but growing populations eventually pushed them back to the large river.
We pass the bottle around the fire, swigging happily and reveling in the burning sensation that the liquor gives the throat. Soon, we are laughing at the wind and our bodies warm up to the idea of sleeping on the side of this volcano. We look from the fiery peak of Fuego to the clear bottle glimmering red in our campfire.
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