How Big Is a Barrel? It Depends Entirely on What Is Inside It
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Casks were made in named sizes that differed by commodity, by country and by century, so the same word describes containers of quite different volumes. Some of those names are still in use.
Why cask sizes were named
Before standard containers, goods travelled in wooden casks made by coopers to sizes that had acquired names, and those names functioned as units of trade, so a cargo could be described and taxed by counting casks rather than measuring contents. That worked only where everybody agreed what a named size held, which is why the sizes were defined in statute repeatedly and why the definitions kept changing. Casks were made in a graded series, with each name a fixed fraction or multiple of the others, so a merchant could convert between them, and the whole system was built around that internal consistency rather than around any external standard.
The English series
The wine measures were defined in law and formed a ladder:
- •A tun, the largest, holding two hundred and fifty two gallons
- •A pipe or butt, half of that
- •A hogshead, a quarter, at sixty three gallons
- •A tierce at a third of a pipe, a barrel at half a hogshead
- •A rundlet and smaller sizes below
- •Beer and ale measures ran on a different and smaller ladder entirely
Why the same name meant different volumes
The confusion is genuine and was not an accident of sloppiness. Different commodities were taxed at different rates and handled by different trades, each with its own established sizes, so the name attached to a cask of beer described a different volume from the same name applied to wine, and different again for cider, tobacco, sugar or molasses. Ale and beer were separately defined and the two differed from each other for centuries. Scottish and Irish measures differed from English ones. And the definitions changed by statute as revenue needs changed, so a document's date matters as much as its subject when converting a historical quantity.
How a cooper made one
Building a watertight vessel from shaped planks with no glue, screws or sealant is one of the more impressive traditional crafts and explains why the sizes were standardised. Each stave is cut with a taper towards both ends and a curve across its width, so that when assembled the staves press against each other along their edges. They are raised inside a hoop, then heated and wetted so they can be drawn in at the far end by a rope and the remaining hoops driven on. The ends are grooved and the flat heads fitted, and the tighter the hoops are driven the more firmly the whole thing seals itself, with no sealing material at all.
What survives
Several of the names remain in working use where the tradition continued. Scotch whisky maturation uses casks of named sizes, with a hogshead of around two hundred and fifty litres assembled from the staves of used bourbon barrels, and butts, puncheons and quarter casks all still specified, since cask size directly affects maturation by changing the ratio of wood to liquid. Wine and sherry use their own surviving names. Brewing retains firkins and kilderkins for cask ale. In each case the name now describes a manufactured size rather than a legal measure, which removes the ambiguity that made the older system so difficult.
The takeaway
Named cask sizes worked as units of trade so goods could be counted rather than measured, which required agreement on what each name held, and that agreement kept changing by statute. Wine ran on one ladder from the tun downward and beer on a different smaller one, with further variations by commodity and country. The names survive in whisky and brewing as manufactured sizes rather than legal measures.