pH testPlease see previous entry for additional information about the Organic Indigo Vat Dyeing workshop taught by Catharine Ellis.

What is Indigo?

Indigo is the ONLY naturally occurring blue dye.

Indigo is a pigment found in several plants around the world including Indigofera tinctoria (grown in India), Indigofer guatamalensis (grown in South America), Isatis tinctoria (woad, grown in Europe), and Polygonum tinctorium (Japanese Indigo).

Indigo pigment is not soluble in water - so in order to turn indigo pigment into dye, you have to create what is called a vat.  To successfully create an indigo vat, you need three things or conditions (in addition to water):

  • Indigo pigment that has already been extracted from the plant
  • An alkaline such as wood ash, lye, or lime
  • You must remove the oxygen from the water ('reduce' the vat)

In other words, you need to create a solution that includes indigo, has a high pH (base), and has very little free oxygen.  Once those conditions have been met, you have a yellow-ish liquid that can dye cellulose or other natural fibers various shades of beautiful blue.

There have been many methods throughout time for putting a vat in a reduced oxygen state.  Historically, this has been done through fermentation.  Fermentation can be a long and very stinky process.  Our society doesn't tend to favor slow processes, so other approaches were developed that use chemical reactions to remove the oxygen - including the use of sodium hydrosulfite or thiorea dioxide.  These chemical methods are much faster, but have a strong chemical smell.

The methods of reduction that Catherine Ellis taught us in this workshop use plant/fruit sugars, anti-oxidants, or minerals to put the vat in a reduced oxygen state.  These are methods that she has learned from Michel Garcia and that she has put to extensive use in her own studio.  Some of the amazing things about these methods are:

  • The vats created by these methods can be ready for dyeing in 24 hours or less
  • They smell earthy - not stinky
  • They produce beautiful, rich, blue colors
  • They are gentler on the environment and the dyer
  • The materials (aside from the indigo) can be inexpensive and readily available
    • You can use pickling lime as your alkaline
    • You can use fruit scraps to extract fruit sugars

Check back for the next entry with a little bit more information about the 4 types of vats we learned to make in this class.

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