European Geologist Journal 42

The firewater trail

By Manuel Regueiro y González-Barros*

*Geological Survey of Spain,

Old Spanish saying: Una gota de aguardiente deja el estómago caliente y hace al hombre fuerte y valiente (A drop of firewater warms the buck and makes a man courageous and tough).



Firewater has accompanied society since early times. This paper is one small section of a yet-to-be-written book titled The Spirits of Europe, which aims to correlate the very varied production of this type of alcoholic drinks in Europe with the geology of the lands where they are produced. The text includes a history of firewater, their types and production modes and presents a representative case in Spain: the geology of the firewater trail.


Brief history of firewater

Although most authors agree that the history of firewater starts with the invention of distillation by Muslims, Berthelot (1885) cites the existence of small alembics or distillation apparatus in the house of “chemists” in Egyptian Alexandria (3rd century B.C.).

The alchemist, pharmacist, philosopher, astronomer, and physicist Jabir ibn Hayyan (died ca. 808 or 815) is considered the father of chemistry. His works – Book of ChemistryThe Balances and others – were translated by Robert of Chester (ca. 1144) and Gerard of Cremona (ca. 1187) in Toledo. Jabir described how boiling wine released a flammable vapour, or spirit. Al-Razi is credited with identifying ethanol, or grain alcohol. In fact the word alcohol derives from the name al-ghawl given to this substance by Muslim chemists, meaning spirit or intoxicant (Qur’an 37:47), incidentially also the source of the English word ghoul (an evil spirit or phantom).

De aqua vitae simplici et compositae of the French physician and alchemist Perarnau de Vilanova, printed in 1332 (Rodríguez Guerrero, 2010-2013), is considered the first work that mentions firewater by its Latin name of aqua vitae, which is still used in Sweden and Norway as aquavit, in Denmark as akuavit and in Italy as acqua vitis or acqua de vite. He thought that alcohol was the universal panacea, the “elixir of eternal life” or the dream of alchemists, sought for centuries, as it was considered a fantastic medicine for use against bubonic plague and other infections, although it had a nasty taste and burnt the throat when drinking it. To mask its bad taste, plants and fruit were added, which also had medicinal properties.

The habit of drinking firewater extended to Germany in the 15th century, where it was considered a refinement more than a medicine; at this time the manufacture of firewater from cereals was discovered. Miguel Savonarola wrote a comprehensive manuscript on firewater and made public a procedure to determine the quantity of alcohol contained in the liquor (Valsecchi, 2010). In 1543 Bavaria imposed a tax on firewater consumption. At the end of the 16th century it had become a very common drink in Sweden, and in Russia its consumption then was already as important as it is today.

Potato firewater was first cited in 1682 in a book edited by Backer (Delgado 2007). The first potato distillery was established in 1759 in Monsheim in the Rhineland-Palatinate (Germany).

The 18th century saw the advent of firewater produced from fruit, berries and cereals, and also its prohibition in some places on the grounds of it being a poison. It was then considered the cause of most crimes and vices, a drink of hell and an invention of the devil; it was fought against by societies, ecclesiastic organisations, religions, etc. In fact this is something that still endures…

Firewater production

Firewater is a drink of high (40 to 65%) alcoholic volumetric content (avc) obtained by the distillation of other liquids and mixtures with a low avc, which are separated using heat, based on the fact that alcohol evaporates at lower temperature than water. At atmospheric pressure both alcohol (ethanol) and water evaporate, but while water boils at 100 ºC, alcohol starts boiling at 78 ºC. Thus, when a mixture of alcohol and water is boiled, alcohol will separate while water will still preserve its liquid state. If alcohol vapours are passed by a coolant an almost pure alcohol will be recovered by condensation.

The time firewater ages in the barrel, in close contact with wood, determines its final properties. Firewater from wine reaches its maximum quality after 15 to 20 years, but gin and other firewater of high avc need very little aging, since after one year they stop improving. The quality of barrels has a great impact on the aging of firewater. Cognac ages in Limousine oak barrels, which improves its quality. Fire-treated white oak provides a special taste to whisky due to tannic substances. In general water evaporates little by little through the wood, so after a certain time the avc rises proportionally to the reduction in the amount of liquid.

Classification of firewater

Firewater can be classified in several ways; here we include a classification based on the source material[1]:

  1. Firewater from wine or grape pomace
  • Brandy (i.e. sherry brandy). Minimum avc 36%Vol. The name comes from Holland, where in order to stock the surplus of the wine harvest, Dutch dealers started to distil and store it in small barrels, calling it brandewinj (burnt wine), a name that was later shortened to brandy.
  • Cognac
  • Armagnac
  • Orujo (from grape marc)
  • Liquors. Hydroalcoholic sweet drinks aromatised with several substances. Avc over 15%.
  • Pisco (a grape brandy from wine)
  1. Firewater from other sources
  • Tequila & Mescal. From agave
  • Kirschwasser. From cherries
  • Shōchū. Typically distilled from barley, sweet potatoes, buckwheat, or rice, though it is sometimes produced from other ingredients such as brown sugar, chestnut, sesame seeds, or even carrots. Japanese.
  • Patxaran, From plum
  • Vodka. A spirit produced by either rectifying ethyl alcohol from fermented cereal grains or potatoes or filtering it through activated charcoal, possibly followed by straightforward distillation or an equivalent treatment. The product may be given special organoleptic characteristics by the addition of flavouring.
  • Cider, mead, palm wine
  • Anisette: anise and badian. Aromatization of ethylic alcohol with aniseed-flavoured essences. Minimum avc 35%.
  1. Firewater from other sugar-containing substances
  • Rum. Obtained from alcoholic fermentation and distillation of molasses or syrup from the manufacture of cane sugar. Minimum avc 37.5%, maximum 96%.
  1. Firewater from grain
    • Distilled from fermented grain mash (malt wine) of barley and or other grains. Owes its characteristic taste to the addition of juniper berries. The name comes from the world geneva, a corruption of the French word genièvre or Dutch junever, both meaning juniper. Dutch gin (Geneva, Genever, Ginebra, Schiedam or Hollands) is produced by adding a third of fermented crushed and rectified malt to low avc alcohol, distilling the mixture and adding flavouring and taste agents and then rectifying it again to produce a final product with an avc 43º to 44º. British gin is produced by rectifying a high avc mixture of whiskeys or other alcoholic mixtures so that they lose flavour and taste. Flavouring is done by adding strawberries as well as orris roots, the herb angelica, almonds, coriander, caraway, cardamom, anise, cassia, lemon peel, orange, etc.
    • Whiskey. Produced by distillation of a mash of cereals and matured for at least three years in wooden casks. Various grains (which may be malted) are used for different varieties, including barley, corn (maize), rye, and wheat, which give the various whisky types: corn whiskey or single malt from one grain, usually barley. A good description of the relation to the important malt whisky producing districts to the geology of Scotland and Northern Ireland and its influences on the taste of a single malt can be read in Cribb and Cribb (1998).


The alembic tradition was introduced in Spain by Muslims with a simple instrument called alquitara, from the Arabic term al-gattara, meaning “that which distils”. It had three connected pieces: a base or support usually made of cast iron, a pot or boiler, and a top condenser, a semi-spherical expansion chamber with a drain or pipe to extract the liquor. The top case has two holes for the water that cools the condenser.

The alembic was the technical evolution of the alquitara, the name comes from al-ambiq which in turn comes from the Greek word ambicos, meaning vase. The main difference is that the alembic separates the vaporisation and condensation sections of the process. An alembic has a copper boiling pot of variable capacity and a top condenser which is prolonged in a long goose neck (or elephant trunk) that ends in cylindrical cooling condenser which contains a copper cooling coil.

Spain has a long tradition in the manufacture of firewater, as it was considered the “drink of the underprivileged” par excellence. There is evidence of the first alquitaras in the year 900 being used to distill wine in the region of Jerez de la Frontera (Fernandez de Bobadilla, 1990).

In Andalusia, the consumption of firewater was traditionally related to hard physical work, such as mining, as it was a custom to drink it before entering the mine, but is also an after-meal drink. Firewater production was originally much diversified in Andalusia, with several cities with a very relevant production, such as Cazalla de la Sierra (Seville) where very strong local firewater was produced, the famous cazalla, or Zalamea la Real, close to the mines of Riotinto and Rute south of Cordoba.

In the northwest, firewater production is typical in Galicia. Galician firewater is produced from the pomace of grapes, from which it takes its traditional name orujo. The European Union recognised the Galician tradition of firewater production in its regulation 1576/89, and authorises in Annex II the name Orujo Gallego for these types of distilled products. Galicia is the sole Spanish firewater producing region mentioned in this EU norm.


The main firewater production centres in Spain can be linked by a line that follows a well-known ancient Spanish trail: The Silver Trail (Figure 1) which has also a geological linkage: the Iberian Massif.

Figure 1: The Silver Trail.

The Silver Trail

The Silver Trail is an old Roman route that crossed Spain south to north, from Merida to Astorga, and today is one of the main north-south bound routes in Spain from Seville to Gijón. The name Silver Trail does not really have to do with the existence of a metal trade, but actually derives from the Arabic word al-balat, which means paved route, and described the road engineered by the Romans. The sound of this word in Spanish resembles that of the word plata (silver), so probably this confusion was the reason why this name was finally adopted.

The Roman route was built during Augustan times (late 1st century B.C.) to link Emérita Augusta (today Mérida), the capital of the then new province of Lusitania, with the northern territories recently incorporated into the Empire after their conquest. The route was later employed for access to the West during the re-conquest of Spain from the Muslims and finally as a pilgrimage route to Santiago de Compostela, a use that is still maintained today. The radial communication system built in Spain from the 18th century reduced its relevance.

Firewater has been produced and traded along the Silver Trail since its first appearance in Andalusia in the Cordoba sultanate of the Muslim Spain. From the famous brandies of Jerez de la Frontera and Puerto de Santa Maria (Cádiz), the firewaters of Valverde del Camino (Huelva), Rute and Montilla (Córdoba), Ronda (Málaga), Atarfe (Granada) and the cazallas of Cazalla de la Sierra in Seville, to the Galician orujos of Orense, Lugo and A Coruña, passing by the firewaters of Extremadura in the Jerte Valley (Cáceres) and in Almendralejo (Badajoz), the trail can be traced by the different and varied types of spirits that today help the pilgrims in their quest for Santiago.

Geology of the Silver Trail

The geological substrate of the main western Spanish firewater production zones is almost entirely included in the Iberia Massif (Figure 2).

Figure 2: The Iberian Massif.

The Iberian Massif represents the Precambrian and Palaeozoic rocks cropping in the western half of the peninsula and is sharply limited to the south by the Guadalquivir Valley with Cainozoic sediments. The Massif shows the most complete European outcrops of the Variscan (or Hercynian) orogeny (Middle Devonian and Carboniferous), the result of the collision of two mega-continents: Laurasia and Gondwana, including also small continental masses such as Armorica and Avalonia, and represents the main part of the Pangea supercontinent.

The Iberian Massif was subdivided by Lotze (1945) into six zones according to their stratigraphic, structural, metamorphic and magmatic characteristics: the Cantabrian Zone, Western Asturian-Leonese Zone, Central Iberian Zone, Galicia-Tras-Os–Montes Zone, Ossa-Morena Zone and South Portuguese Zone. These correspond  to their position in the old orogeny, thus the Cantabrian and South Portuguese zones are the most external zones, with sediments formed during the orogeny (sin-orogenic) and folds and thrusts tilted to the outside of the chain, whilst the rest of the zones are internal regions with very important deformations, metamorphism and magmatism.

The main firewater production zones in the Silver Trail are geologically located south to north in the Guadalquivir Tertiary basin and three zones of the Iberian Massif.

  • Guadalquivir Tertiary Basin

The Guadalquivir Basin is an ENE-WSW elongated depression filled with Neogene sediments where the famous brandies of Jerez de la Frontera and Puerto de Santa Maria (Cádiz) are produced. It is a foreland basin located between the Betic Range at the south (active border) and the Iberian Massif (passive border). The substrate of most white firewater white wine producing regions of Burdigalian–Langian–Serravalian age  are formed by moronite or albarizas facies (“whitish) mainly composed by white marls rich in foraminifera, cocolites and diatoms from deep marine environments.

  • Ossa-Morena Zone

The firewaters of Valverde del Camino (Huelva), Rute and Montilla (Córdoba) and the cazallas of Cazalla de la Sierra (Seville), are produced in areas with rocks from Precambrian to the Palaeozoic of a continental block merged during the Variscan Orogeny, generally characterised by low to medium metamorphism and a tectonic foliation related to metamorphic phases. The limits of the zone are marked by rocks of oceanic affinity (ophiolites), which indicates the closure of oceanic zones and suture of continental blocks.

  • Central Iberian Zone

This is the widest and largest part of the Massif. It corresponds to the central parts of the Variscan orogeny and presents an important amount of granitic batholiths. The firewaters of Extremadura in the Jerte Valley (Cáceres) and in Almendralejo (Badajoz) are produced in this geological zone, which is limited to the north by the Vivero fault and to the south by the Central Unit of the share zone of Badajoz-Cordoba. Stratigraphically it stands out for the transgressive character of the Lower Ordovician, for the pre-eminence of the pre-Ordovician materials and for the uniformity of the Ordovician and Silurian materials in almost all the zone. The Variscan orogeny magmatism is very well developed in the zone, with alochtonous granites from in-situ melting of pre-orogenic materials.

  • Galicia-Trás-os-Montes Zone

The northwest of the Massif corresponds to a complex group of alochtonous sheets thrusting 300 km over the Central Iberian Zone. The terrains have a varied source as fragments of oceanic crust or of a volcanic arc and are the source of most Galician orujos of Orense, Lugo and A Coruña. This zone has two superimposed thrusting sub-domains, genetically independent. The lower Palaeozoic dominium shows siliciclastic sediments and metavulcanites, and the upper dominium was formed by accretion of materials from very different sources, ophiolitic materials from oceanic crust in several units of the Ordenes and Cabo Ortegal complexes and mixed materials from continental or potential island arch sources, which all together seem to point to the suture of the closure of the Rethic Ocean.


Firewater has a deep geological connection, be it for the waters used in the manufacture of the different varieties, or because of the geological subsurface under the soils where the awesome variety of plants employed in its production are grown. The taste of firewater is also the result of the fantastic combination of original plants, waters, soil and subsoil types (from igneous to sedimentary or metamorphic rocks) and the elaborating process.

Firewater has been produced and traded along the Spanish Silver Trail since its first appearance in Andalusia in the Cordoba sultanate of the Muslim Spain. The Silver Trail follows a well-known N-S Precambrian and Palaeozoic geological structure: the Iberian Massif. From the famous brandies of Jerez de la Frontera and Puerto de Santa Maria (Cádiz), the firewaters of Valverde del Camino (Huelva), Rute and Montilla (Córdoba), Ronda (Málaga), Atarfe (Granada) and the cazallas of Cazalla de la Sierra in Seville, to the Galician orujos of Orense, Lugo and A Coruña, passing by the firewaters of Extremadura in the Jerte Valley (Cáceres) and in Almendralejo (Badajoz), the trail can be traced by the different and varied types of spirits that today help the pilgrims in their quest for Santiago.

[1] A more detailed classification at the European level can be found in Council Regulation (EEC) No 1576/89 of 29 May 1989, laying down general rules on the definition, description and presentation of spirit drinks.


Berthelot, M. (1885). Los orígenes de la alquimia.(The origins of Alchemy) Ed facsímil MRA Ediciones, España. Madrid. 2013.

Cribb, S., Cribb, J. (1998). Whisky on the Rocks: Origins of the Water of Life. Earthwise Popular Science Books, Keyworth, Nottingham, British Geological Survey.

Delgado, C. (2007). El libro de los aguardientes y licores. The book of firewater. Alianza Editorial.

Fernández de Bobadilla, V. (1990). El Brandy de Jerez. The Brandy of Jerez. Madrid, CRYSESA Ed.

Lotze, F. (1945). Zur gliederung der Variszichen der lberischen Meseta. Geotektonísche Forschungen, 6, 78-92.

Rodríguez Guerrero, J. (2010-2013). El origen del pseudo-arnaldiano liber de vinis.(The origins of the pseudo-arnaldian liber de vinis). Azogue, 7.

Valsecchi, P. (2010). El moderno destilador-licorista. (The modern distillator-liquorish) Ed Maxtor. Ed facsímil.

This article has been published in European Geologist Journal 42 – International cooperation on raw materials.