Fermentation is the ninth of the twelve stages of alchemy, part of the yellow stage (citrinitas). It is the quickening of the work: a little ferment is added, like yeast to dough, and the whole work rises and glows. In spiritual alchemy it is the return of joy, play and inspiration after the long clearing.
What the alchemists did
Fermentation meant adding a ferment, a small quantity of gold or of the prepared stone, the way yeast is worked into dough, so that the whole mass was quickened. The alchemists described a play of many colours in the vessel, which they called the peacock’s tail.
What it means in you
Fermentation is the stage of new life. The alchemists added a little ferment, like yeast to dough, and the whole work began to rise and glow with colours they called the peacock’s tail. This is the first gate of New Light. After the long clearing, joy, play and inspiration come back. This week is about letting them.
Its engraving: Basil Valentine’s Eighth Key
Basil Valentine’s Eighth Key, from the Musaeum Hermeticum. Photograph: Wellcome Collection, CC BY 4.0; colours added.
Gate 9 carries the Eighth Key of Basil Valentine’s Twelve Keys, the key of sowing and rising. A seed must rot in the earth before it grows; the farmer knows this without knowing why.
In the old masters’ words
“There is no ferment otherwise than from the dough itself.” Hermes Trismegistus, The Golden Tractate
“Whenever the water comes rolling back, it brings a blessing with it.” Basil Valentine, The Twelve Keys, 1599
A question to sit with
What feels alive in you lately?
When did you first notice it?
What does it want?
How could you give it more room?
From the app’s daily quiz
What did the alchemists call the stage when every colour appears in the vessel? The peacock’s tail. Philalethes said the colours were too many to describe.
In Fermentation, the alchemists added a little ferment, like… Yeast to dough. And the whole work began to rise and glow.
Eudoxus said the deepest knowledge comes more by… Inspiration. Gate 9 is the week of letting joy and inspiration back in.
Pernety wrote that every person keeps within them… A spark of the first light. Gate 9 ends with that spark.
Basil Valentine said the artist brings new things out of… The seed already given. Making is drawing out what is already there.
In Lead to Gold
In Lead to Gold, Fermentation is Gate 9 of the Great Work, in the New light part of the path. Its seven days: Rising dough, The peacock’s tail, Inspiration, Joy, Making, It spreads, The spark. Each day has a short lesson, a guided exercise with the Glass, and a prompt to reflect on.
Last updated October 25, 2026.
Lead to Gold: Shadow Work, on Google Play
The alchemists’ Great Work, made into ten quiet minutes a day: twelve gates, a private journal, and a line of wisdom from the old masters. Free to download, for Android.
What is sublimation in alchemy?: Sublimation, stage 8 of the twelve stages of alchemy: rising above. What the alchemists did, and what it means for you.
What is exaltation in alchemy?: Exaltation, stage 10 of the twelve stages of alchemy: raising it to its highest. What the alchemists did, and what it means for you.
What does Basil Valentine’s Eighth Key mean?: Basil Valentine’s Eighth Key (1599) explained: why the seed must rot before it grows, the four elements in everything, and the full text in English.
What are the stages of alchemy?: The stages of alchemy: nigredo, albedo, citrinitas and rubedo, and the twelve operations from Calcination to Projection, each explained in plain words.
