Currently, most countries have no legal definition of absinthe, although spirits such as Scotch whisky, brandy, and gin generally have such a definition. Manufacturers can label a product “absinthe” or “absinth” without regard to any legal definition or minimum standard. Producers of legitimate absinthes use one of two processes to create the finished spirit: either distillation, or cold mixing. In the few countries which have a legal definition of absinthe, distillation is the sole permitted process. An online description of the distillation process (in French) is available.
Distilled absinthe is produced in a form similar to high quality gin. The botanicals are macerated in the already distilled alcohol before being redistilled one or more times with the herbal ingredients to impart complexity and texture to the beverage.The distillation of absinthe first produces a colourless distillate that leaves the alembic at around 72 percent ABV (144 proof). The distillate can be bottled clear, to produce a Blanche or la Bleue absinthe, or it can be coloured using artificial or natural colouring. Traditional absinthes take their green colour from chlorophyll, which is present in some of the herbal ingredients during the secondary maceration.The natural colouring process is considered critical for absinthe ageing, since the chlorophyll remains chemically active. The chlorophyll plays the same role in absinthe that tannins do in wine or brown liquors.This is done by steeping petite wormwood, hyssop, and melissa (among other herbs) in the liquid. Chlorophyll from these herbs is extracted giving the drink its famous green colour. This process also provides the herbal complexity that is typical of high quality absinthe. This type of absinthe is known as a verte. After the colouring process, the resulting product is diluted with water to the desired percentage of alcohol. Historically, most absinthes contain between 50 and 75 percent alcohol by volume (100 to 150 proof). It is said to improve materially with storage, and many pre-ban distilleries aged their absinthe in neutral barrels before bottling.
Many modern absinthes are produced using the cold mix system. This process is forbidden in countries with formal legal designations of absinthe. The beverage is manufactured by mixing flavouring essences and artificial colouring in high-proof alcohol, and is similar to a flavoured vodka or “absinthe schnapps”. Some modern Franco–Suisse absinthes are bottled at up to 82.3 percent alcohol and some modern bohemian-style absinthes contain up to 89.9 percent. Because of the lack of a formal legal definition of absinthe in most countries, many of these lesser brands claim their products to be “distilled” (since the alcohol base itself was created through distillation) and sell them at prices comparable to more authentic absinthes that are distilled directly from whole herbs.