Proof (alcohol)
Encyclopedia
Alcohol proof is a measure of how much alcohol
(ethanol
) is contained in an alcoholic beverage
. The term was originally used in the United Kingdom
and was defined as 7/4 times the alcohol by volume
(abv). The UK now uses the abv standard instead of alcohol proof. In the United States
, alcoholic proof is defined as twice the percentage of abv. The measurement of alcohol content and the statement of this content on the bottle
labels of distilled beverage
s (also called liquors or spirits) is regulated by law in the United States. The purpose of the regulation is to provide pertinent information to the consumer.
of gunpowder
. The term originated in the 18th century, when payments to British sailors included rations of rum
. To ensure that the rum had not been watered down, it was “proved” by dousing gunpowder
in it, then tested to see if the gunpowder would ignite. If it did not, then the rum contained too much water and was considered to be “under proof”. It was found that gunpowder would not burn in rum that contained less than 57.15% abv. Therefore, rum that contained this percentage of alcohol was defined to have "100 degrees proof".
An alcohol content of 57.15% abv is very close to a 4:7 ratio
of alcohol to the total volume of the liquid. Thus, the definition amounted to declaring that (4÷7) × 175 = 100 degrees proof spirit. From this it followed that pure, 100% alcohol had (7÷7) × 175 = 175 degrees proof spirit, and that rum containing 50% abv had (3.5÷7) × 175 = 87.5 degrees proof spirit. To convert the percentage of abv to degrees proof spirit, it was only necessary to multiply the percentage by 1.75.
The use of "proof" as a measure of alcohol content is now mostly historical. Today, liquor
is sold with labels that state its alcohol content as its percentage of alcohol by volume
(abv). United States law requires that liquor labels must state the percentage of alcohol by volume. The proof number may also be placed on the label, provided that it is close to the abv number.
Many countries also use a measure called a standard drink
. In Australia
, a standard drink contains 10 g (12.67 ml) of alcohol, the amount that an average adult male can metabolise in one hour. The purpose of the standard drink measure is to help drinkers monitor and control their alcohol intake.
From the 1740s until 1816, Customs and Excise and London
brewers
and distillers used Clarke’s hydrometer
to measure degrees proof. Under the Hydrometer Act of 1818, the Sikes hydrometer was used to measure proof; it remained in use until 1980. The Customs and Excise Act of 1952 defined “spirits of proof strength” (i.e., proof spirits):
follows recommendations of the International Organization of Legal Metrology
(OIML). OIML's International Recommendation No. 22 (1973) provides standards for measuring alcohol strength by volume
and by mass
. A preference for one method over the other is not stated in the document, but if alcohol strength by volume is used, it must be expressed as a percentage (%) of total volume, and the water/alcohol mixture must have a temperature of 20°C when measurement is done. The document does not address alcohol proof or the labeling of bottles.
(27 CFR [4-1-03 Edition] §5.37 Alcohol content) requires that liquor labels must state the percentage of abv. The regulation permits, but does not require, a statement of the proof provided that it is printed close to the abv number. For bottled spirits over 100 ml containing no solids, actual alcohol content is allowed to vary within 0.15% of abv stated on the label. Alcohol proof in the United States is defined as twice the percentage of alcohol by volume. Consequently, 100-proof whiskey contains 50% alcohol by volume; 86-proof whiskey contains 43% alcohol. The terminology used in the United States is "n" proof, where "n" is a number — not "n" degrees proof. The term "degrees proof" is not used.
.
, alcohol content is 3–12% abv, but it is most often 4–6%. Conventional wine
s will have 9–16% abv, with most being between 12.5–14.5%. Fortified wine
s, such as port
, madeira
, marsala
, sherry
, and vermouth
, have 15.5–20% abv. The wine is “fortified” by adding a distilled spirit, usually brandy
, to it. Stronger drinks, such as liquors, are distilled
after fermentation
to increase their alcohol content. These form a very broad category of beverages whose alcohol content can range from 20% to 95% abv. Old recipes may reference second proof (60% abv or 120 proof), third proof (70% abv or 140 proof), or fourth proof spirits (80% abv or 160 proof).
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
(ethanol
Ethanol
Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...
) is contained in an alcoholic beverage
Alcoholic beverage
An alcoholic beverage is a drink containing ethanol, commonly known as alcohol. Alcoholic beverages are divided into three general classes: beers, wines, and spirits. They are legally consumed in most countries, and over 100 countries have laws regulating their production, sale, and consumption...
. The term was originally used in the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
and was defined as 7/4 times the alcohol by volume
Alcohol by volume
Alcohol by volume is a standard measure of how much alcohol is contained in an alcoholic beverage .The ABV standard is used worldwide....
(abv). The UK now uses the abv standard instead of alcohol proof. In the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, alcoholic proof is defined as twice the percentage of abv. The measurement of alcohol content and the statement of this content on the bottle
Bottle
A bottle is a rigid container with a neck that is narrower than the body and a "mouth". By contrast, a jar has a relatively large mouth or opening. Bottles are often made of glass, clay, plastic, aluminum or other impervious materials, and typically used to store liquids such as water, milk, soft...
labels of distilled beverage
Distilled beverage
A distilled beverage, liquor, or spirit is an alcoholic beverage containing ethanol that is produced by distilling ethanol produced by means of fermenting grain, fruit, or vegetables...
s (also called liquors or spirits) is regulated by law in the United States. The purpose of the regulation is to provide pertinent information to the consumer.
History
In the 18th century and until 1 January 1980, the United Kingdom defined alcohol content in terms of “proof spirit”, which was defined as the most dilute spirit that would sustain combustionCombustion
Combustion or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can result in the production of light in the form of either glowing or a flame...
of gunpowder
Gunpowder
Gunpowder, also known since in the late 19th century as black powder, was the first chemical explosive and the only one known until the mid 1800s. It is a mixture of sulfur, charcoal, and potassium nitrate - with the sulfur and charcoal acting as fuels, while the saltpeter works as an oxidizer...
. The term originated in the 18th century, when payments to British sailors included rations of rum
Rum
Rum is a distilled alcoholic beverage made from sugarcane by-products such as molasses, or directly from sugarcane juice, by a process of fermentation and distillation. The distillate, a clear liquid, is then usually aged in oak barrels...
. To ensure that the rum had not been watered down, it was “proved” by dousing gunpowder
Gunpowder
Gunpowder, also known since in the late 19th century as black powder, was the first chemical explosive and the only one known until the mid 1800s. It is a mixture of sulfur, charcoal, and potassium nitrate - with the sulfur and charcoal acting as fuels, while the saltpeter works as an oxidizer...
in it, then tested to see if the gunpowder would ignite. If it did not, then the rum contained too much water and was considered to be “under proof”. It was found that gunpowder would not burn in rum that contained less than 57.15% abv. Therefore, rum that contained this percentage of alcohol was defined to have "100 degrees proof".
An alcohol content of 57.15% abv is very close to a 4:7 ratio
Ratio
In mathematics, a ratio is a relationship between two numbers of the same kind , usually expressed as "a to b" or a:b, sometimes expressed arithmetically as a dimensionless quotient of the two which explicitly indicates how many times the first number contains the second In mathematics, a ratio is...
of alcohol to the total volume of the liquid. Thus, the definition amounted to declaring that (4÷7) × 175 = 100 degrees proof spirit. From this it followed that pure, 100% alcohol had (7÷7) × 175 = 175 degrees proof spirit, and that rum containing 50% abv had (3.5÷7) × 175 = 87.5 degrees proof spirit. To convert the percentage of abv to degrees proof spirit, it was only necessary to multiply the percentage by 1.75.
The use of "proof" as a measure of alcohol content is now mostly historical. Today, liquor
Distilled beverage
A distilled beverage, liquor, or spirit is an alcoholic beverage containing ethanol that is produced by distilling ethanol produced by means of fermenting grain, fruit, or vegetables...
is sold with labels that state its alcohol content as its percentage of alcohol by volume
Alcohol by volume
Alcohol by volume is a standard measure of how much alcohol is contained in an alcoholic beverage .The ABV standard is used worldwide....
(abv). United States law requires that liquor labels must state the percentage of alcohol by volume. The proof number may also be placed on the label, provided that it is close to the abv number.
Many countries also use a measure called a standard drink
Standard drink
A standard drink is a notional drink that contains a specified amount of pure alcohol. The standard drink is used in many countries to quantify alcohol intake. It is usually re-expressed as a measure of beer, wine, or spirits for convenience. One standard drink always contains the same amount of...
. In Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, a standard drink contains 10 g (12.67 ml) of alcohol, the amount that an average adult male can metabolise in one hour. The purpose of the standard drink measure is to help drinkers monitor and control their alcohol intake.
From the 1740s until 1816, Customs and Excise and London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...
brewers
Brewing
Brewing is the production of beer through steeping a starch source in water and then fermenting with yeast. Brewing has taken place since around the 6th millennium BCE, and archeological evidence suggests that this technique was used in ancient Egypt...
and distillers used Clarke’s hydrometer
Hydrometer
A hydrometer is an instrument used to measure the specific gravity of liquids; that is, the ratio of the density of the liquid to the density of water....
to measure degrees proof. Under the Hydrometer Act of 1818, the Sikes hydrometer was used to measure proof; it remained in use until 1980. The Customs and Excise Act of 1952 defined “spirits of proof strength” (i.e., proof spirits):
“Spirits shall be deemed to be at proof if the volume of the ethyl alcohol contained therein made up to the volume of the spirits with distilled waterDistilled waterDistilled water is water that has many of its impurities removed through distillation. Distillation involves boiling the water and then condensing the steam into a clean container.-History:...
has a weight equal to that of twelve-thirteenths of a volume of distilled water equal to the volume of the spirits, the volume of each liquid being computed as at fifty-one degrees Fahrenheit.”
European Union
The European UnionEuropean Union
The European Union is an economic and political union of 27 independent member states which are located primarily in Europe. The EU traces its origins from the European Coal and Steel Community and the European Economic Community , formed by six countries in 1958...
follows recommendations of the International Organization of Legal Metrology
International Organization of Legal Metrology
The International Organization of Legal Metrology or Organisation Internationale de Métrologie Légale is an intergovernmental treaty organization. The OIML currently has 57 Member States and 58 Corresponding Members...
(OIML). OIML's International Recommendation No. 22 (1973) provides standards for measuring alcohol strength by volume
Volume
Volume is the quantity of three-dimensional space enclosed by some closed boundary, for example, the space that a substance or shape occupies or contains....
and by mass
Mass
Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...
. A preference for one method over the other is not stated in the document, but if alcohol strength by volume is used, it must be expressed as a percentage (%) of total volume, and the water/alcohol mixture must have a temperature of 20°C when measurement is done. The document does not address alcohol proof or the labeling of bottles.
United States
In the United States, alcohol content is measured in terms of the percentage of alcohol by volume. The Code of Federal RegulationsCode of Federal Regulations
The Code of Federal Regulations is the codification of the general and permanent rules and regulations published in the Federal Register by the executive departments and agencies of the Federal Government of the United States.The CFR is published by the Office of the Federal Register, an agency...
(27 CFR [4-1-03 Edition] §5.37 Alcohol content) requires that liquor labels must state the percentage of abv. The regulation permits, but does not require, a statement of the proof provided that it is printed close to the abv number. For bottled spirits over 100 ml containing no solids, actual alcohol content is allowed to vary within 0.15% of abv stated on the label. Alcohol proof in the United States is defined as twice the percentage of alcohol by volume. Consequently, 100-proof whiskey contains 50% alcohol by volume; 86-proof whiskey contains 43% alcohol. The terminology used in the United States is "n" proof, where "n" is a number — not "n" degrees proof. The term "degrees proof" is not used.
United Kingdom
Since 1 January 1980, the United Kingdom has used the abv standard to measure alcohol content, as prescribed by the European UnionEuropean Union
The European Union is an economic and political union of 27 independent member states which are located primarily in Europe. The EU traces its origins from the European Coal and Steel Community and the European Economic Community , formed by six countries in 1958...
.
“In common with other ECEuropean UnionThe European Union is an economic and political union of 27 independent member states which are located primarily in Europe. The EU traces its origins from the European Coal and Steel Community and the European Economic Community , formed by six countries in 1958...
countries, on 1st January, 1980, BritainUnited KingdomThe United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
adopted the system of measurement recommended by the International Organisation of Legal Metrology, a body with most major nations among its members. The OIML system measures alcohol strength as a percentage of alcohol by volume at a temperature of 20°C. It replaced the Sikes system of measuring the proof strength of spiritsDistilled beverageA distilled beverage, liquor, or spirit is an alcoholic beverage containing ethanol that is produced by distilling ethanol produced by means of fermenting grain, fruit, or vegetables...
, which had been used in Britain for over 160 years.”
“BritainUnited KingdomThe United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
, which used to use the Sikes scale to display proof, now uses the European scale set down by the International Organization of Legal Metrology (IOLM). This scale, for all intents and purposes the same as the Gay-Lussac scale previously used by much of mainland Europe, was adopted by all the countries in the European CommunityEuropean UnionThe European Union is an economic and political union of 27 independent member states which are located primarily in Europe. The EU traces its origins from the European Coal and Steel Community and the European Economic Community , formed by six countries in 1958...
in 1980. Using the IOLM scale or the Gay-Lussac scale is essentially the same as measuring alcohol by volume except that the figures are expressed in degrees, not percentages.”
Alcohol content in beverage production
In beerBeer
Beer is the world's most widely consumed andprobably oldest alcoholic beverage; it is the third most popular drink overall, after water and tea. It is produced by the brewing and fermentation of sugars, mainly derived from malted cereal grains, most commonly malted barley and malted wheat...
, alcohol content is 3–12% abv, but it is most often 4–6%. Conventional wine
Wine
Wine is an alcoholic beverage, made of fermented fruit juice, usually from grapes. The natural chemical balance of grapes lets them ferment without the addition of sugars, acids, enzymes, or other nutrients. Grape wine is produced by fermenting crushed grapes using various types of yeast. Yeast...
s will have 9–16% abv, with most being between 12.5–14.5%. Fortified wine
Fortified wine
Fortified wine is wine to which a distilled beverage has been added. Fortified wine is distinguished from spirits made from wine in that spirits are produced by means of distillation, while fortified wine is simply wine that has had a spirit added to it...
s, such as port
Port wine
Port wine is a Portuguese fortified wine produced exclusively in the Douro Valley in the northern provinces of Portugal. It is typically a sweet, red wine, often served as a dessert wine, and comes in dry, semi-dry, and white varieties...
, madeira
Madeira wine
Madeira is a fortified Portuguese wine made in the Madeira Islands. Some wines produced in small quantities in California and Texas are also referred to as "Madeira", or "Madera", although those wines do not conform to the EU PDO regulations...
, marsala
Marsala wine
Marsala is a wine produced in the region surrounding the Italian city of Marsala in Sicily. Marsala wine first received Denominazione di Origine Controllata status in 1969....
, sherry
Sherry
Sherry is a fortified wine made from white grapes that are grown near the town of Jerez , Spain. In Spanish, it is called vino de Jerez....
, and vermouth
Vermouth
Vermouth is a fortified wine flavored with various dry ingredients. The modern versions of the beverage were first produced around the late 18th and early 19th centuries in Italy and France...
, have 15.5–20% abv. The wine is “fortified” by adding a distilled spirit, usually brandy
Brandy
Brandy is a spirit produced by distilling wine. Brandy generally contains 35%–60% alcohol by volume and is typically taken as an after-dinner drink...
, to it. Stronger drinks, such as liquors, are distilled
Distillation
Distillation is a method of separating mixtures based on differences in volatilities of components in a boiling liquid mixture. Distillation is a unit operation, or a physical separation process, and not a chemical reaction....
after fermentation
Fermentation (food)
Fermentation in food processing typically is the conversion of carbohydrates to alcohols and carbon dioxide or organic acids using yeasts, bacteria, or a combination thereof, under anaerobic conditions. Fermentation in simple terms is the chemical conversion of sugars into ethanol...
to increase their alcohol content. These form a very broad category of beverages whose alcohol content can range from 20% to 95% abv. Old recipes may reference second proof (60% abv or 120 proof), third proof (70% abv or 140 proof), or fourth proof spirits (80% abv or 160 proof).