Proof

I was researching a venerable Irish whiskey recently and came across an old newspaper ad that described the whiskey as "25 degrees under proof".

These days we define alcoholic strength in terms of percentage alcohol by volume (ABV). So I wondered how to convert the older measure to its modern equivalent.

The term proof goes back a few hundred years, originating, so the story goes, with sailors suspicious that their grog ration had been watered down.

To "prove" the strength of the spirit, a dish of gunpowder was doused in the alcohol and set alight. If the gunpowder took fire, the spirit was over proof. If it did not the spirit was under proof.

Since this is not terribly scientific, parliament subsequently laid down that thirteen volumes of proof spirit is equal to the weight of twelve volumes of water, all measurements being made at 51°F.

The strength of all mixtures of alcohol and water could then be defined relative to this fixed point. They would be described as some number under or over proof, that number describing how many volumes of water should be added to or subtracted from a hundred volumes of the mixture to produce proof spirit.

Ten over proof, for example, means that ten volumes of water should be added to a hundred volumes of the spirit to make it proof.

Of course proof is defined differently in the United States. There, proof number is twice the percentage of the alcohol content measured by volume at a temperature of 60°F.

To go from US proof number to %ABV is very easy: just divide by two.

According to Merriam-Webster's Guide to Everyday Math, we can convert American proof to British proof by multiplying by 7/8.

All of which is a roundabout way of arriving at a simple formula to convert 25 degrees under proof to %ABV. We can express 25 degrees under proof as 75 proof. Convert to American proof by multiplying by 8, then dividing by 7. Then divide by 2 to get %ABV.

Or just multiply by 4/7 to get there directly. 25 under proof is the equivalent of just under 43% ABV.

Butts, hogsheads, pipes and puncheons

Before the European Union forced the bottling of drinks in their country of origin, the wine merchants of the British Isles imported sherry, port, rum and other commodities by the cask.

Once the contents were sold the merchants often bought the fresh output of the whiskey distilleries, refilled the casks and left the spirit to mature in their own bonded warehouses.

Such refilled casks are still crucial to the aging process. These days, however, they are imported almost dry while the liquid they once contained makes its way separately in glass bottles.

There were many types of cask with wonderful names that depended on their size, contents and where they had come from.

We still see these names on whiskey labels today: "aged in a single sherry hogshead", "finished in port pipes", and so on.

Definitions are a little awkward because these are very old measures and come from a time when the volume of a gallon varied depending on the liquid being measured. In 1824, when England finally standardised the gallon (to be known as the "imperial" gallon), they made it different to the US gallon.

We can be reasonably correct in saying the following, however. A "butt" and a "pipe" hold the same quantity, either of which contains twice the amount in a "hogshead".

A "puncheon" (also called a "firkin") holds about a third more than a hogshead.

Another type that one hears about in whiskey circles is the "quarter cask". They are not typically used, due to the cost of using small, expensively crafted casks. But distilleries do experiment with them, including, apparently, Cooley. I believe the cask being quartered is the butt. So a quarter cask is half a hogshead. I'm open to correction.

Does cask size matter? It does. The smaller the cask, the more rapidly the whiskey ages because proportionately more liquid is in contact with the wood.

For fun, here are a few definitions from The Dictionary of Trade, Commerce and Navigation, published in London in 1844. Along with the terms mentioned above, I have included a few more to indicate that the variety in wooden casks was greater than even that indicated on whiskey labels.

I also added "back" and "tun". These terms for large wooden vessels have also survived in the whiskey industry, though not in the context of maturation. We will cover them later.

The gallons are imperial (1 imperial gal = 1.2 US gals).

ANKER

A liquid measure originating at Amsterdam containing 10.25 gallons English. The anker is the cask used by smugglers hence we hear of an anker of brandy or more familiarly tub of brandy; half this measure is called with us a pin.

BAC OR BACK

A cask of a very large size, as of 3, 4, or 500 gallons. The makers of such backs are called back makers and not coopers. Backs have been made so large as to hold 12,000 barrels. Such are used principally in breweries and distilleries to hold spirits, beer or water.

BARREL

A wooden vessel made by the cooper of staves bound together by hoops and closed at both ends. Also a measure of capacity for liquids. A Barrel of Beer is equal to 36 gallons.

BUTT

A vessel or measure for wine, beer, etc. containing two hogsheads and varying in quantity according to the kind of wine.

HOGSHEAD

A measure of capacity containing 52.5 imperial gallons or 63 old wine gallons and 54 old beer gallons. A hogshead is also a nominal quantity and varies in exact amount according to the contents. The word hogshead in this more extended sense referring rather to the vessel than to the liquid within it. Thus the hogsheads in which different kinds of wine are imported differ very materially in capacity.

PIPE

A liquid measure chiefly used for wine and spirits and varying much in quantity according to the kind of wine which it contains. The standard pipe is equal to 2 hogsheads or 108 gallons but few casks are found of this exact capacity. The term pipe, and its equivalent, butt, no less than its half, the hogshead, being now considered as specifying a particular kind of cask rather than any determinate quantity. Thus, the pipe of port is equal to 115 imperial gallons; pipe of Lisbon 117 gallons; pipe of Cape or Madeira 92 gallons; pipe of Teneriffe 100 gallons; butt of sherry 108 gallons; hogshead of claret 46 gallons. Purchasers are always charged the actual quantity the vessel contains.

PUNCHEON

A liquid measure of capacity equal in general to 84 gallons but varying slightly with different liquors. The largest sized cask in which rum is imported is called a rum puncheon whatever be its size.

TIERCE OR TEIRCE

A measure indicating 42 gallons or a cask of about that capacity. The tierce is used for oil and still more for the packing of salted beef or pork for ship's use.

TUN

A liquid measure = 252 gallons.

Drinking for your country - whiskey and tax

If you live in Ireland and you feel a hand in your pocket on Wednesday, that would be Brian Cowen, our finance minister, paying for his recent 15.6% pay rise.

Yup, it's Budget Day. We have been warned that the purse strings must be tightened because the economy is running out of steam. Whiskey drinkers have even more cause to worry since the Health Service Executive recently called for a 10% rise in alcohol duties to curb excessive consumption.

In fact, Ireland is already one of the most expensive places in the world to buy a bottle of whiskey. An Irish Times survey earlier in the year discovered that a standard 70cl bottle of Jameson costing between €24 and €29 in Ireland would only set you back €12 in Spain, €14 in the US, €15 in England and €16 in France.

A large part of the explanation is tax. There are two kinds of tax on alcohol: duty and VAT (Value Added Tax, similar to sales tax in other countries).

Duty is based on the alcohol content alone. VAT is based on price. As if to mock us, duty is added first then VAT is calculated on the duty-inclusive price. So we are paying tax on tax.

For whiskey, duty is €39.25 per litre of alcohol. Note, not per litre of whiskey. So for a litre of whiskey containg 40% alcohol by volume (ABV), the duty payable is 40% x €39.25 = €15.70.

This is one reason, incidentally, that supermarket whiskey brands are always 40% ABV. Any higher and more duty would be payable. Any lower and it would not legally be whiskey.

VAT is 21% for whiskey. It's calculated on the retail price (ex-VAT) including duty.

Let's work an actual example. If a 70cl bottle of Jameson (40% ABV) costs you €26, how much are you donating to the Exchequer?

€26 includes 21% VAT so the amount of VAT is €4.51. The duty is 40% x 0.7l x €39.25 which is €10.99.

So total taxes are €4.51 + €10.99 = €15.50. As a percentage of the final price paid, that's 59.6%. So let's say 60% of the price you pay goes to the government. For a more expensive whiskey the percentage will drop (since duty remains constant as long the alcohol content is the same).

It's no wonder we have managed to crush what was once a strong indigenous industry. For comparison, the VAT rate in the UK is 17.5% and excise duty is €27.26 (£19.56) per litre of alcohol. That's substantially less than applies in Ireland, yet the Scotch Whisky Association, representing the whisky trade in Scotland, still regards this level of duty as "punitive and discriminatory".

Update Wednesday, Dec 5: We dodged a bullet. Alcohol duty was left unchanged. But the Minister warns us that he may not be so lenient next year:

It has also been suggested to me that there might be public health benefits arising from a switch to lower alcohol beverages. This will require some study, and indeed some adjustments by industry – I am giving notice now that I intend to bring forward measures in this area in my next Budget.

Table of Irish Whiskeys

The table of Irish whiskeys is finally ready. It's not 100% complete (I can think of a few not present) but there are already about 65 entries.

There are no supermarket own brands listed. There are quite a few of those but they tend to be unpeaty blends at 40% ABV so they won't add many surprises if I eventually get around to listing them.

I'll probably add a column for "peatedness" in the near future and perhaps one for chill-filtering after that.

Comments and suggestions welcome.