The alchemists though pursuing their inner work independently as individuals, nevertheless found in their interior descent a coherent language of symbols. At the core of this was a vision of an alchemical process occurring through a cycle of colour changes, from an initial blackness to the perfection of the quintessence. The alchemist envisaged each stage of the process being heralded by a colour change and a meeting with certain animals:
Blackening - Black Crow, Raven, Toad, Massa Confusa.
Whitening - White Swan, White Eagle, skeleton.
Greening - Green Lion.
Rapid cycling through iridescent colours - Peacock's Tail.
White Stone - Unicorn.
Reddening - Pelican feeding young with its own blood, cockerel.
Final transmutation - Phoenix reborn from the fire.
The phase of Blackening which usually marked the beginning of the work, was brought about either by heating the prima materia in the process of Calcination (the 'dry way' of the alchemists), or by the process of Putrefaction, a slow rotting or digestion over a period of weeks or months (the so-called 'wet way'). The Black Crow or Raven was often associated with this Calcination, for on vigorous heating the calcined material would usually carbonise and layers would flake off and move like a crow's wings in the flask. The Toad was a better symbol of the Putrefaction, the decaying mass slowly pulsating and shifting as gasses were given off, while the substance rotted down to a black mass. Another symbol of this stage was the dragon, a familiar inhabitant of the alchemists flasks. The dragon is however a more complex symbol and is also used when winged as a symbol for the spiritualising of the earthly substance. Thus to the alchemists the dragon appeared at the beginning and at the end of the work.
The alchemists paralleled these experiences in their souls as a withdrawal into the darkness of their interior space, a darkness pregnant with possibility. We have to a great extent lost the sense that still lived in the medieval and renaissance alchemists, that this darkness contained all potentialities. Like children we fear the dark, and for twentieth century humanity darkness often holds only an existential dread - philosophers of science have in the last decade brought us this terrible image of the 'Black Hole' which swallows up and annihilates everything that comes into its orbit. Perhaps we do not gaze enough at the blackness of the heavens. For if we look deep into the blackness of space on a clear night, we will sense more stars hidden between the known visible stars, especially in the vast star fields of the Milky Way. Cosmic space is pregnant with the possibility of other worlds as yet unseen. It is this image of blackness we must try to recover if we are to become alchemists. An echo of this perhaps remains in the often used phrase "a profound darkness".
Thus alchemists could pursue their cycle of inner transformation as embarking on a journey in which they met with archetypal animal figures. The steps on their journey were paralleled in their experiments in their flasks, and the detailed images of processes of change were worked together with the animal archetypes of that stage into a mandala-like picture which they used as the basis for their meditations. (Animal Alchemy)