Sunday, March 15, 2009

Woad Indigo -- a science fair project phase 3

The final stages of the student's science fair project are in process. The paper is written -- over 40 pages about woad -- its history, chemistry, biology, art and economics. The statistical analysis is done. The board was finished at midnight on Thursday night in time for the first round of science fairs.

The biggest enouragement is that the indigo yield from her woad doubled this year over last year. And it was the rainiest and coldest summer we've seen, so this is a positive finding.

She saved seed in our Canadian zone 3 range land climate, at 2700ft. elevation with summer frosts. The saved woad seed out performed the seed from 2007 and out performed the mean yields of current scientific studies -- done on prime agricultural land in Europe and UK. Wow!

Plus her own saved woad seed is rich in indigo precursors through out the growing season, unlike the purchased seed which looses most of its precursors in the early Fall, after frost.

She's getting an average of 4 to 6 grams of indigo per kg. of woad leaves using her innovative extraction method. Last year she averaged 2 gram of indigo per kg. of leaves -- the same as the European studies. According to the Maiwa documentary, "Indigo", the tropical indigo averages 5 grams of indigo per kg. of leaves, using a fermentation extraction method.

The usual method of indigo extraction from woad follows the method described by
Beijerinck in 1900, where hot water is poured over woad leaves and they are allowed to steep for several hours before being removed from the extraction vat. This method is inefficient and results in a loss of most of the indigo precursors from the extraction, since isatan A and isatan B -- the most abundant precursors in woad -- are unstable and require specialized extraction conditions. Woad has an undeserved reputation as a poor source of indigo dye pigment. By improving the extraction methods and using a seed selected for high indigo precursor content, the yields of blue pigment from woad can rival tropical indigo.

The student's method optimizes the indigo yield by taking advantage of the precursors and obtains up to 8 grams per kg. of leaves in some extractions -- averaging 4 grams per kg. of leaves over 50 extractions.

The student took first place in the High School Science Fair on Friday and is on her way to the regional science fair in April. Visit to find out more.

Woad dyed tapestry in mohair and wool with a cotton warp. Designed, dyed and woven by the student. All colours came from woad.

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