The Firing process

The I Ching is a book about the firing process or the firing times.

The Can Tong Qi (Triplex Unity, 2nd century Taoist text) sees the hexagrams #1 Heaven and #2 Earth as crucible and furnace and hexagrams #29 Mastering Pitfalls and #30 Fire as the medicinal ingredients. Therefore the rest of the remaining 60 hexagrams stand for the firing times. -- Yu Yan (13th c. Taoist master, Commentary on Cantong Qi - 2nd c. Taoist text))
The firing process spoken of in the alchemical classics and writings of the masters is a metaphor for the order of practical spiritual work.
-- Liu Yiming (The Inner Teachings of Taoism)
For the firing process, the classics speak of the I Ching hexagrams; But it is wrong to ponder the lines and cling to the images. It is all a matter of needing to understand the principles of yin and yang; Advance and withdraw according to the time, as is indicated.
-- Liu Yiming (The Inner Teachings of Taoism)

Fire is a symbol for illumination or conscious awareness.

Fire is a symbol of illumination; operating the fire means employing illumination. Illumination is the quality of awareness and perceptivity. If one can be aware, then one has the mind of Tao, and the spirit is knowing. If one can be perceptive, then there is no human mentality, and the mind is clear. -- Liu Yiming (The Taoist I Ching, Hexagram 55 Richness)

Conscious awareness or the illumination of the mind of Tao is true yang energy.

It is necessary to know this firing process of advancing yang.
-- Liu Yiming (The Taoist I Ching, Hexagram #1 Heaven)

The firing process needs a crucible and furnace.

Set up the crucible and furnace.
Stabilize the will with firmness; do the work with flexibility.
Making the will firm and strong is setting up the crucible;
Gradually progressing in the work is setting up the furnace.
Firmness and flexibility are both used, without imbalance;
Having prepared, work the fire and the convergence according to the time. -- Liu Yiming (The Inner Teachings of Taoism)

A balance of yang and yin, refering to firmness and flexibility, are necessary for the firing process to burn away false yin to reach pure yang. Firmness refers to not allowing one`s conscious awareness to be pulled away by upcoming thoughts. Flexibility refers to the firing process progressing and reaching pure yang.

Only when yin and yang are harmoniously combined is it possible to accomplish things. Therefore the way of tranquility is that the small goes and the great comes; it is auspicious and developmental. The small is yin and the great is yang: "The small goes" means yin submits, "the great comes" means yang is strong. With yang strong on the inside and yin submissive on the outside, the primordial gradually returns and acquired conditioning gradually melts away; thereby it is possible to reach the realm of pure yang with no yin. It is a matter of course then to be fortunate in action, and for activity to develop. -- Liu Yiming (The Taoist I Ching, Hexagram #11 Tranquility)

The firing process starts with hexagram #24 Return, which represents the return of yang energy.

Return ䷗ means coming back.......The way to do it involves working in sequence, restoring it gradually; one cannot restore it immediately, or even if one does restore it immediately it cannot be stabilized. It is necessary to first refine oneself and master the mind,
-- Liu Yiming, The Taoist I Ching, hexagram 24 Return
The point where one yang begins to move is when the yang light of real perception of the mind of Tao stirs but is not yet very active. At this time you should quickly set about increasing the fire, gathering yang and putting it into the furnace of evolution, gradually gathering, gradually refining, from vagueness to clarity, from one yang to complete purity of six yangs. This is also like the mid-autumn moon, exceptionally bright, shining through the universe.
-- Liu Yiming (Commentary on Understandng Reality)

The firing process refers to a six-step process, going from one yang to the pure wholeness of six yangs. During this process the influence of the human mind gradually decreases so that the Original Spirit (also called the Gold Elixir) can come into being.

The six stages of purification by fire ...are in sequence and should never be mixed up; only then can it produce the Golden Elixir.
-- Chao Pi Chen (20th c. Taoist master)
The true fire is one`s own spirit: the true times are one`s own breathing. Refining the medicine by means of fire in order to form the Elixir is like spirit driving breath in order to attest the Tao.
-- Zhu Yuanyu (17th c. Taoist master, Commentary on the Cantong Qi

The six steps of the firing process are timed with one`s breathing in order to retrieve the true or immortal breath.

One who mounts the truth of Heaven and Earth rides the changes of the six breaths, and then roams amongst the boundless.
-- Zhuangzi (4th c. BCE Taoist master)
Although this true breath is linked with postnatal (ordinary) breathing, the latter coming in-and-out through the mouth and nostrils, cannot reach the original cavity of spirit to return to the source. In your quest for immortal breath, you should regulate postnatal (ordinary) breathing in order to find its source. -- Chao Pi Chen, (20th c.Taoist Master)

Ordinary breathing keeps the body alive, the immortal breath or Breath of Life makes the Original Spirit alive. During six ordinary breaths one keeps one`s conscious awareness on one`s breathing without allowing any interruption. This means one has to let all thoughts pass by without paying attention to them. This is called bathing.

Bath and incubate. Do not let thoughts arise; do not let attention scatter. -- Liu Yiming (The Inner teachings of Taoism)

The secret within the secret cannot be dispensed with from start to finish. This is the washing of the heart and the purification of the thoughts, which is bathing. -- The Secret of the Golden Flower

From start to finish refers to the first and sixth breath.

But to practice what is beneficial, it is important to have a beginning and a conclusion. If there is a beginning but no conclusion, one's acts are still of no benefit — there is no gain, but loss.
-- Liu Yiming (The Taoist I Ching, Hexagram #42 increase)
How can the wonder of the fire phases be something easy to know? People nowadays do not know that the fire phases are extremely fine and subtle. They cling to the ancient saying, “With one word or half a sentence you comprehend the Mystery”, and they just say that the fire phases cannot be spoken and cannot be transmitted. They do not know what is the wonder of that one word or half a sentence. “The words murmured in a whisper”, by a true master reveal a fragment of the secret of the celestial mechanism; they do not transmit the fire phases in words. -- Liu Yiming, (Cultivating the Tao)
I've got a spell called True Words to calm the mind.
-- Journey to the West, Ch 14

One word refers to a word that reminds one to stay aware of one`s breathing. Half a sentence refers to the six words murmered in a whisper — spoken silently to oneself, accompanying six breaths.

The inner development of the elixir and the timing of it`s firing are no different at all from the ebbing and the flowing of the phases of the moon. The six lines of the Heaven hexagram act as an image of the waxing and waning of the moon`s body. But it`s all metaphor.
-- Yu Yan (Commentary on the Cantong Qi

The firing process has two stages, action or doing and non-action or non-doing.

As for the path of cultivating life, this is the path of doing. Doing is based on action, and requires adjustment of the outer furnace, diligent effort at refinement. This is using the martial fire for cooking. Adjustment means increasing and decreasing: increasing means increasing real awareness where it is insufficient, picking out the good and cleaving to it; decreasing means decreasing the excess of conscious awareness, getting rid of intellectualism. The path of cultivating essence is the path of non-doing, or non-action. Non-doing is based on stillness, and doesn't involve any action; keeping to the middle, embracing oneness, the inner furnace has of itself a real fire which ever glows crimson. This is using the cultural fire for incubation. -- Liu Yiming, Understanding Reality)
The secret of the elixir of life consists in using action in order to attain non-action. -- The Secret of the Golden Flower, Chapter 1

The process of action is shown in the first six ox herding pictures when the bull (a metaphor for the lower self or discriminating spirit) gradually becomes white, symbolizing that mundane yin energy has been burned away so that the discriminating spirit is no longer veling the original spirit and pure yang has been reached. The last four ox herding pictures represent the process of non-doing.

This hexagram (#26 Nurturing the Great) represents incubation nurturing the spiritual embryo; it follows on the previous hexagram Return. Return means restoration of the primordial energy. When the primordial energy comes back within, slight and vague to begin with, then becoming clearly evident, it restores the original self; the foundation of life is stabilized, the spiritual embryo is formed, and one enters from action into non-action. Then one should carefully seal it and store it securely, forestalling danger, incubating and bathing, aiming for the great transformation, the unfathomable state of spiritual sublimation, making it indestructible and incorruptible. -- Liu Yiming, The Taoist I Ching, hexagram 26 Nurturance of the Great

Hexagram #2 Earth

Hexagram #30 Mastering pitfalls

A Japanese fire fesival, an external representation of the firing process
(Click to enlarge)

The trigrams Heaven and Earth,
symbolizing the crucible and furnace;
firmness and flexibility

Yin and Yang harmoniously combined (Bangkok, Thailand)
(Click to enlarge)

A watercolour painting by Willam Blake:
Our times are fixed and our days are numbered

Sun Wukong, the Monkey King of the Journey to the West and the full moon.

God the Father (representing the Original Spirit) and Christ (representing the mind of Tao) have the same face, meaning they are different aspects in the same person. They are exchanging the breath of Life.
(Click to enlarge)

Hathor, giving the breath of life to the Pharaoh (Egyptian Museum, Cairo)

Two Nio Guardians standing at the entrance gate of a Buddhist temple. They represent beginning and end. (13th C. AD, Todaji temple, Nara , Japan) (Click to enlarge)

The monk Kuya Shonin, repeating Amida Buddha`s name six times. (by Kosho, 13th Century, Rokuharamitsuji temple, Kyoto)

Hexagram #1 Heaven

Hexagram #24 Return

Hexagram #26 Nurturance of the Great.
Above is the trigram Mountain symbolizing stillness and below the trigram Heaven representing the celestial energy of
the original self.