Andalusia, situated in Spain's southwest corner, is a cultural hub centred around the cities of Sevilla, Cordoba, Granada and Ronda.  Their citizens celebrate flamenco dancing to the sounds of guitars, salt-cured ham, and hundreds of years of history, all lubricated by the wonderful sherry produced there.

  And that sherry-producing region is located just 50 kilometres south of Sevilla, adjacent to the Gulf of Cadiz. It's enclosed by three ancient cities with romantic names; Jerez de la Frontera at the northeast corner, Sanlúcar de Barrameda at the western apex, and El Puerto de Santa Maria to the southeast.  There, the vineyards, heated by long sunny days and nourished in the white albariza chalk soils, produce several varieties of crisp white grapes.  But it is in the barrels, termed pipes, in which the unique flor yeast grows, transforming these grapes from wine to sherry.  This mass of fungus, enhanced by the maritime climate, sits atop the wine in the headspace left in the barrel.  Besides protecting the wine from oxidizing, through its biochemical reactions, it creates sherry's enchanting flavours and aromas.

  One would think for a yeast living in a barrel, atop some lovely Fino, Amontillado or Oloroso, it would be the cat’s meow.  Not so, the yeast cells are stressed, living in concentrations of high ethanol and ending in starvation when the nutrients in the wines are depleted.  Tough life!  
   As with the barrels for the port wines, the sherry pipes' importance in its production derives largely from the ability to age the wines rather than from the specific flavours coming from the oak.  In combination with the yeast, the many years within the casks refine and mature the sherries varieties.
   Within vast warehouses, where the barrels are stacked three to five high in long rows, thick stone walls keep the temperatures cool or at least moderated.  These pyramidal assembles facilitate the ageing and sherry's year-to-year consistency, achieved by transferring portions of the wines from barrel to barrel in a process termed the solera system.  It works like this; from one end of a stack, a portion of the oldest wines are removed for bottling.  Then the next oldest wines, taken from other barrels in the stack, are transferred to refill those barrels.  The subsequent oldest wines then refill those barrels.  And so on until the year's new wines are added to the barrels at the opposite end.  

Today, there are several active cooperages, located primarily around Jerez de la Frontera, supplying hundreds of new barrels to the sherry bodegas.  Made mostly from American oak, the majority of the casks go into the solera process.  But some are used to briefly age certain sherries, leaving a trace of their flavour in the oak, before being sent to those Scot whisky distilleries that want the nuance of sherry in their whisky.      
   Years ago, sherry was a popular drink, especially in Britain.  By the 1980s, however, that market soured on the low-quality, inexpensive sherry then being produced.  As that demand dried up, vineyards were abandoned or taken over by other developments.  Now, according to a recent article by Eric Asimov* a few producers are relooking at some of the older, more resilient grapes and specific vineyard sites that produce higher-quality wines.  Selecting these, these winemakers are raising the bar on various sherries and regional wines.  Worth asking your liquor retailer about.

   
*Asimov, Eric (29 June 2023) In Sherry Country, Wines of the Future That Look to the Past.  New York Times.