Real eau de cologne is made from essential oils, usually Bergamot, Neroli, Lavender and Rosemary, though other citrus oils (Orange, Lemon and Petitgrain) may be included, and occasionally Thyme is used in place of Rosemary.

The formula was originally devised in the first decade of the eighteenth century by Johann-Maria Farina, a German-naturalised Italian who lived in Cologne, and called his aromatic blend 'Kolnisches Wasser' after the town. It rapidly became well-known for its cooling, refreshing, deodorant and antiseptic properties. It is not quite certain whether Farina or one of his descendants later changed the name to the French equivalent to make it sound more elegant, and possibly give the product a wider appeal, or whether this came about when French soldiers, stationed in Cologne during the Seven Years War, took samples home with them. With the change of name, the maker's signature on the labels was also Gallicised to Jean-Marie Farina. The head of the firm was called Johann-Maria, or Jean-Marie, for many generations, as each successive son or nephew christened his eldest son after the founder.

By the end of the eighteenth century many perfumiers throughout Europe were making their own versions of eau de cologne, among them several Farinas who had no connection with the originator (Farina is not an uncommon name in Italy) but who benefited from the resulting confusion. The original firm in Cologne has remained in the same family right into the present century, though many colognes labelled 'J-M. Farina' originate elsewhere.

Napoleon used vast quantities of eau de cologne - in the region of 600 bottles a year - and never travelled without it, even on military 'campaigns. When we consider the properties of the essential oils used in making the toilet water, it is easy to understand how valuable it would have been to a fastidious person in the unsanitary conditions of a military encampment. In Napoleon's time, cologne was often called 'Aqua Admirabilis' in recognition of its many virtues.

The quality of an eau de cologne depends as much on the alcohol used as a base as on the essential oils blended with it. The original Kolnisches Wasser was made with highly rectified potato alcohol, in plentiful supply in Germany, but modern colognes are usually based on perfume-grade ethyl alcohol. The blend of alcohol and essential oils is left to rest for at least six months and really good colognes are matured for a year. Perfumery alcohol cannot be bought without a Customs and Excise licence, and is never available in small quantities, but you can make a cologne-scented bath or body oil by blending the appropriate essential oils in a bland oil base. Or you might try using a high-proof vodka as a substitute for ethyl alcohol.

There are many versions of the eau de cologne formula, but a typical one is:

Essential oil of Bergamot 100 drops
Essential oil of Lemon 50 drops
Essential oil of Neroli 30 drops
Essential oil of Lavender 50 drops
Essential oil of Rosemary 10 drops.

Add this to 150 mls of high-proof vodka to make a toilet-water strength, or to 100 mls of almond or other oils as a bath oil. For a body or massage oil double the amount of carrier oil to 300 mls. You could also use this blend as a bath oil without further mixing, using 6 to 8 drops for an average bath. Leave it in a dark and cool place for as long as you can, to mature before using. If you want to experiment with a small quantity, divide all the amounts by ten. This makes a very citrussy cologne, but you might like to vary the proportions of the oils to make your own favourite version.