Fermentation

Fermentation is counted the fifth of the seven operations into which the alchemical Great Work is often divided. In the laboratory it named the introduction of a living ferment to quicken the joined matter.

Operation and its meaning

Read symbolically, as the alchemists read their own work, Fermentation stood for the infusing of new life into the work, often figured as a putrefaction from which a fresh growth arises. In the scheme of correspondences that links the operations to the seven classical planets, it is attributed to the Moon.

The alchemists worked at once with real chemical processes and with a language of spiritual transformation, so that a single term carried both a bench meaning and an inner one. The operation is described here within that documented tradition of European alchemy, whose sources run from the Hellenistic and Arabic writers through the Latin Middle Ages and the early modern laboratory.

Fermentation is the operation in which the alchemists were closest to a process the modern world understands completely, and furthest from understanding it themselves.

What the word describes

Fermentatio means the change a substance undergoes when a small quantity of an active material is added to a larger inert mass and the whole is left in gentle warmth. Bread, wine and beer were the everyday models, and the sources use them constantly. Closely related in the literature is putrefactio, the rotting that precedes the change, which some authors treat as a separate operation and some as the same one under another name.

That a pinch of leaven can transform a whole vessel was, before microbiology, one of the most genuinely astonishing observable facts available, and the alchemical use of it as a model for transmutation is a reasonable inference from what could be seen.

Where the number seven comes from

A numbered sequence of exactly seven operations tied to the seven planets is a modern arrangement. Historical treatises vary: Ripley's fifteenth-century Compound of Alchymy has twelve gates, and fermentation and putrefaction appear as separate items in some lists and as one in others.

The atlas records the seven-step scheme as the version in general circulation and records here that it smooths over a real disagreement in the sources.