‘A gin and tonic, please.’ The bartender looks around at approximately 150 gins in the bar: ‘Which one? And which tonic would you like, from our choice of around 12?’

This is a huge shift from 20 years ago, when Australian bars would perhaps have three or four gins and one or two tonic waters. The changes in Australia, and in North America and the UK, are a result of the changes in regulations that have allowed small craft distilleries to flourish – but more about these later.

So, what is gin?

In its simplest form, gin is a mixture of flavoursome botanicals, water and pure alcohol (ethanol) distilled to produce a distillate, which is then diluted with water to produce a ‘distilled’ gin, or simply a mixture of botanicals steeped in a mixture of pure alcohol and water, filtered and then diluted with water to bottle strength (about 40% alcohol by volume (ABV)) – so-called ‘bathtub’ gin. The botanicals, by law in Europe and in the US, must include juniper berries (Juniperus communis) and the gin must derive its main characteristic flavour from juniper berries and be bottled at not less than 40% ABV (80° proof) in the US, 37.5% ABV in Europe. Gin may be aged in oak containers. In Australia, there are no official regulations other than to be called a spirit it must have a minimum of 37% ABV.

A typical gin contains juniper berries, coriander seed, angelica root, perhaps licorice root and … and ... the possibilities are endless. In their seminal paper ‘Controlling gin flavor’ in Industrial and Engineering Chemistry, Herman Willke, C.S.  Boruff and Darrell Althausen presented a standard gin formula. Despite the statement in this paper that ‘This formula is used purely for illustrative purpose and does not represent a true potable gin production formula’, many gins winning local and international awards probably have a starting point based on this formulation.

The array of possible botanicals used in producing traditional gin is impressive but this is dwarfed by the almost infinite array when considering the native and indigenous plants used in modern craft gins, not to mention exotic items such as oyster shell, wood ash and elephant dung.

History of gin making

The consumption of spirits produced by the fermentation of carbohydrate feedstocks does not appear to have had a definite beginning, but for possibly as long as 2000–2500 years the distillation of alcohol was for the purpose of producing medicines. Early production of whiskies in Ireland and Scotland, and grape brandies in continental Europe, more than 1000 years ago was for the purpose of producing medicinal spirit. The earliest records of juniper berries in an alcoholic distillate date back to 1657 in John French’s The art of distillation where the botanical list contains 63 herbs, seeds and other flavourants, in addition to juniper, including dwarf elder pith, rhubarb, lignum aloes and amber. After maceration in white spirit, sugar was added and a red-hot gold bar was plunged into the liquid prior to distillation. This resulting spirit is noted as ‘being a very good cure for infections’.

Towards the end of the 17th century, there was a shift in attitude and the consumption of distilled drinks moved into the realm of social pleasure. The distiller of London (1698) describes a recipe including juniper in a distilled spirit that resembles a drink for pleasure rather than medicine.

Gin (or ‘geneva’) came to England from Holland (where it was known as genever/jenever) in the late 17th century, encouraged by William of Orange and Mary, who removed taxes to encourage the distillers of London to produce the spirit. These early gins had a spirit base of a doubled-distilled malt spirit resembling a light-bodied whisky rather than the clean, neutral spirit employed today. Early recipes are presented in Ambrose Cooper’s The complete distiller (1757) where a recipe calls for 3 pounds (1.4 kilograms) of juniper berries, 10 gallons (37 litres) of proof spirit and 4 gallons (15 litres) of clean water, distilled to make 10 gallons of Royal Geneva. The common alehouse version was to distil 10 gallons of malt spirit (a weak spirit probably less than 30% ABV), 2 ounces of oil of turpentine and three handfuls of bay salt. This spirit was then diluted with water to drinking strength. Indeed, many of the early recipes contained oil of turpentine as well as juniper berries, which is understandable as the major constituent of oil of turpentine is α-pinene, the principal component of juniper oil.

The popularity of gin gained ground in England to the extent that, by the early 18th century, London alone had more than 7000 gin shops and gin consumption had become excessive. The heavy consumption of gin and its impacts on society were the basis of Hogarth’s Gin Lane and Beer Street, depicting the evils of the consumption of gin as a contrast to the merits of drinking beer (of much lower alcohol content). The Gin Acts of 1729 and 1736 (known as the ‘50 Pound Act’) were introduced to impose taxes on the production and consumption of gin. These acts led to public riots in 1743 and they were repealed, but in 1751 a new Gin Act was introduced, by again imposing heavy taxes. However, by this date the government of the day had an alternative drink for the masses – tea – and tea consumption replaced that of gin.

The production of gin took a back seat, with only a few major distillers such as Booths, Gilbeys, Seagrams Beefeater and Gordons/Tanqueray starting operations in the latter part of the 19th century.

Fast forward to 1990 in Australia. In Tasmania, the law that existed in relation to the production of spirit (the Distillation Prohibition Act 1839 had been repealed in 1847) was the Distillation Act 1901 (legislation.gov.au/Details/C2004H01100), which, apart from requiring a substantial bond, required (wash) stills to be no smaller than 2700 litres. This was far larger than any emerging craft distiller could justify. Enter Bill Lark, a person with a passion for making premium quality whisky. He spoke to local MP Duncan Kerr about the discriminatory nature of the law, and Kerr relayed this to Barry Jones, the then federal minister for Small Business and Customs. With a stroke of the pen, the law was changed without having to go through Parliament. In 1992, Bill Lark and his wife, Lyn, set up the first legal distillery in Tasmania since 1882 with a 60-litre copper pot still, and began to produce whisky.

This legislative change was truly pioneering – various states in the US have only relatively recently changed their legislation (e.g. California Craft Distillers Act 2015) to allow craft distilleries to compete with larger producers, and in the UK in 2009 the Excise Act 1823 was amended to allow stills of less than 1800 litres capacity to operate.

Modern gins and methods of production

Early in the gin distillation process, a small ‘heads cut’ is taken to remove the less desirable lower boiling point compounds. Following is the ‘hearts’ or ‘spirits’ cut, which is the gin component, and then perhaps a continuation of the distillation to recover all alcohol (the ‘tails’). For the larger producers, the still size may be of the order of 3000–12 000 litres while for craft distillers the stills may be 30–2500 litres and larger.

The neutral spirit at approximately 95–96% ABV is usually sourced from a third party. Traditionally, this has come from a wheat base, although in Australia neutral spirit is obtained from cereal, sugar and grape feedstocks. The neutral spirit has to meet particular specifications relating to the maximum amounts of higher alcohols, esters, aldehydes, methanol and other components. A small number of craft distillers make their own neutral spirit through fermentation of a feedstock, usually sugar or grapes, followed by distillation.

The still pot is charged with the neutral spirit and water to give a resulting ABV of 30–50% or higher. The botanicals are usually added to the pot, although a large number of craft gin producers put their botanicals in a gin basket placed in the lyne arm. Many producers place a component of the botanicals in the pot, with some going into the gin basket. Other producers place baskets at the base of the column to hold the botanicals, or at the top of the column (known as a Carter head). Some producers steep the botanicals in the pot solution for up to 36 hours at room or slightly elevated temperature prior to distillation.

Alcohol and water are miscible in all proportions and the boiling (bubble) point of the mixture is a function of composition. The equilibrium diagram above shows what happens to the liquid and vapour compositions during a typical distillation run. Starting at a pot composition of 48.5% ABV, the liquid boils at 82.4ºC (a) and a vapour composition of 82% ABV (b). As the distillation continues, the pot composition falls to 17% ABV (c) and a distillate composition of about 64% ABV (d), at which the collection of gin spirit is terminated. These numbers are important because all the volatiles in the botanicals are hydrophobic and have boiling points well in excess of the temperatures reached in a gin distillation.

Their presence and concentration in the distillate is a function of their partial vapour pressures and are determined by their volatilities, and these depend on the composition of bulk vapour, i.e. ethanol–water composition. Deterre et al. (J. Chem. Eng. Data 2012, vol. 57, pp. 3344–56) showed that these volatiles increase dramatically at lower ethanol concentration. This has a great impact on flavour and the flavour profile extracted from the botanicals. The use of the gin basket subjects the botanicals to high-alcohol, low-water regimes in contrast to placing the botanicals in the still pot. Some producers employ a rectifier column to increase the alcohol concentration of the vapours even further before entering the gin basket in order to produce a lighter spirit. The characteristics of the final spirit are a matter of horses for courses and personal preference.

Don’t forget the tonic!

The gin scene continues to expand, with more than 330 gin distilleries in Australia in 2022 (fewer than six in 2000) and similar impressive increases in North America (75 going to 2273) and the UK. And where would gin be without tonic water? The number and types of tonics available has risen quickly over the past few years. The combination of gin and tonic was made popular in India during the 19th century as a means of making the dose of antimalarial quinine (in tonic water) more palatable. The legal limits for quinine in modern tonic are 100 ppm in Australia and 83 ppm in the US, and the therapeutic dose of quinine is between 500 and 1000 ppm, so one can only assume that the quinine levels in early tonic were considerably higher than what they are today or that taking gin and tonic in medicinal quantities was quite intoxicating.

Cheers!