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Extraction of Woad

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:

  1. the soaking
  2. the oxidation
  3. the precipitation
  4. the refining and grinding
Soaking of woad
 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.
Oxidation of woad
 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.

Precipitation of woad
 Phase 3 : the precipitation
When the oxidation is complete, the liquid will be transferred into the resting vats.
refining and grinding of woad
 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.


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