The process of Fermentation is typically regarded as being composed of two steps in both laboratory and psycho-spiritual alchemy.
The first phase is known as putrefaction, in which the matter undergoes a second death and is cleansed of all remaining impurities. It is somewhat similar to the first phase of alchemy, calcination, in which the heavy dross of the material is burned off. The putrefaction is the final cleansing of the substance undergoing alchemical transformation.
The second part, or the true fermentation, began with a display of colors known as the cauda pavonis, or peacock’s tail.
In this second part of fermentation, the alchemist may experience visions or engage with psychic energies in a process known as active imagination. The alchemist may also experience fermentation through meaningful or prophetic dreams, out-of-body experiences, or through the use of entheogens or other mind-altering substances.
This fifth step of alchemy is critical in the Great Work, as through this process the seeker is given guidance and inspiration for how to continue on the path toward enlightenment.