The blue pigment does not exist as such in the leaves of the plant. The woad leaf contains a precursor called : Isatan B, which has the specific properties of producing a transparent indoxyle.
It’s the association of 2 molecules contained in the indoxyle, which, in the contact of oxygene, will produce the blue pigment. In this form, the pigment is insolvable.
Our extraction unit has 8 vats in cascade.
The extraction is done in 4 steps:
|Phase 1 : the soaking|
|In certain temperature and water conditions, the Woad leaves will begin to ferment and the pigment will start to mix in the water in a transparent form.|
|Phase 2 : the oxidation|
|The transparent pigment will be put in contact of oygene (pump) and the pigment will change from transparent to green, then green to blue.
The oxidation phase takes 5 hours.
|Phase 3 : the precipitation|
|When the oxidation is complete, the liquid will be transferred into the resting vats.|
|Phase 4 : the refining and grinding|
|The pigment, filtered at around 100 microns, will be washed and then refined.
Then paste will be dried and then crushed to obtain the famous “Blue Gold”.
We will need 1 ton of fresh leaves for only 2 kgs of pure Woad pigment.