The Romans have been credited with devising the barrel; a much stronger and more easily moved container than its predecessor, the amphora. They also gave us the word for those who make them: coopers (L. cupa = tub). The trade – or rather art - of cooperage is thus very old and highly skilled.
Many woods have been tried for cooperage but oak is widely accepted as the best, being strong, free of knots and resin, leakproof and suitably porous. Of the hundreds of oak species, American White oak (Quercus Alba) is the chosen type for Sherry producers. It comes from the eastern half of the USA and the best source is between the Ozarks and the Appalachians, south of the Great Lakes. Here it grows in huge forests and thus grows tall and straight giving good yields for barrel staves. It was in use in Spain by the second half of the XVII century.
In the past most bodegas had their own “trabajadero” or cooperage where butts were made and repaired. In more recent times however the volume of trade has declined and wines are no longer exported in butts, but rather in bottle. Thus many bodegas simply employ a cooper when butts need repair, and new butts- mostly destined for the spirits industry - are made in specialised cooperages. Many of these firms offer a service called “envinado” or seasoning, whereby new butts are seasoned with Sherry before being sent off for maturing spirits like Whisky and Rum. This is now big business, so the Consejo Regulador tries to keep a track of it to ensure that spirits claiming to have been aged in Sherry casks really have been.
Unlike makers of table wine, Sherry producers make strenuous efforts to avoid wood flavours in the wine. New barrels are no use for Sherry as they give off unwanted tannins and woody flavours. Once a new butt has been made it will be used for up to 10 years to ferment wine before it will be deemed suitable for ageing Sherry, especially the more delicate Fino or Manzanilla. It might then be in use for a century or more and will inevitably need repair at some time. If a stave breaks it will be replaced by an old one as a new one would affect the flavour of the wine. Bodegas keep stocks of old staves and hoops for just this purpose. Butts are painted black using a special inert paint, and this makes it much easier to spot a leak.
Bodegas employ members of another highly skilled old trade, that of the “arrumbador”. The job of these hardy men, among other things like running the solera scales, is to stack the barrels, remove any leaking ones and replace them. This is arduous and skilled work. Butts may not be filled to capacity to allow airspace, especially in the case of biologically aged wines. If the butt is full it is referred to as “a tocadedos” meaning you can touch the wine with a finger. Over years of ageing in butts many Sherries develop higher alcohol levels and this is due to transpiration, by which water slowly escapes through the pores of the wood leaving the wine more concentrated.
Sherry “botas” or “butts” come in all shapes and sizes but the following are the most common and most relevant to the consumer. The symbol @ in Spanish means “arroba” which is an old unit of measurement equating to 16.67 litres.
Bota bodeguera (bodega butt) has 26 staves and 10 hoops, capacity 34 @ (567L)
Bota de extracción/embarque (export butt) has 24 staves and 10 hoops, capacity 30 @ (500L). This is the classic “Sherry cask” used in the spirits industry.
Bota gorda: has 27 staves and 10 hoops, capacity 36 @ (600L)
Bocoy: slightly shorter and fatter than a bota gorda, capacity over 40 @ (700L+)
Tonel: is a large barrel in the same shape as a butt, capacity is anywhere between 50 and 120 @ (800-2,000L) sometimes used for the solera in Sanlúcar
Tonelete: smaller tonel, capacity 40-50 @ (700-800L)
Photo Credit: Ralf Bender