Ai(Japanese natural indigo)(Original)

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I looked many books about Japanese textiles during this holiday. We will introduce some interesting information in the future news letter. Today, we would like to write about natural ai. We have written about natural ai more than several times, and most our customers have to know about Japanese natural ai.

In olden times, Japanese people cultivated ai, and dyed their clothes with it. However, dyeing with natural ai is a very elaborate work, and around of Meiji period(1910-1920), synthetic indigo was imported, and natural ai was replaced by it rapidly. Synthetic ai was way cheaper than natural ai, and easy to handle and dye. Its blue color was very similar to natural ai, and ordinary people couldn't tell the difference. It is natural because the molecular architecture of synthetic indigo and the chief component of natural ai is identical.

More about natural ai, please refer John san's page and the page below.
http://www.johnmarshall.to/9-conversations007a.htm
http://www.mukogawa-u.ac.jp/~ushida/e_ai_exp.htm

However, dyer and connoisseurs continue to say that the colors of natural ai and synthetic ai is completely different. Their main affirmations about the difference are

Natural ai is more
1)brightly-colored
2)unequal coloration
3)wash-fastness
4)less bleeding

It must be correct, but we don't have scientific evidence about it, and some people say it is a kind of religion. And we also thought it was difficult to say why they are different.
However, several days ago, I searched in the internet, and found the interesting academic papers! During these several years, I searched again and again, but there was not such page. There had to be persons who had similar question as we had, and wanted to evince the difference scientifically and they proved it!
http://www.jstage.jst.go.jp/article/fiber/63/2/P_48/_pdf/-char/ja/

Unfortunately the text is written only in Japanese. It is difficult to translate all text, but we would like to introduce the essentials with figure.

Natural indigo and synthetic indigo are identical, but their connection forms are different. Distance of two molecules of synthetic indigo is narrower. So the amplitude of the natural indigo is bigger. All differences of natural and synthetic indigo come from this difference.

Both natural and synthetic ai(indigo) are too big to sink into the textile, so they can not dye as they are. To put them into the fabric, dyer removes the bonds of two molecules. Its process is 'reduction', and yellow molecules soluble in water and can sink into the textile(they are smaller than the holes of surface of textile).

After the single molecules sink into the textile, dyer rebuilds the bonds. This process is 'oxidization', and it is simply made by exposing to the air. Molecules become bigger again, and they are difficult to go out from the holes of the textiles('dyed'). Process of natural and synthetic are same, but difference occurs from the size. Synthetic indigo is smaller, so it is easier to get out from the textile(it explains the third aspect above, `wash-fastness'). And from their study, it is understood that molecules of natural ai pair up near the surface of the textile. They say it will explain the first aspect, `brightly-colored') of natural ai.

Because of the amplitude, molecules of natural ai is difficult to move in the textile, so it will be the reason of the fourth aspect above, `soaked less'). Dyers say, to dye the fine patterns with shibori technique, they must use natural ai, because synthetic ai bleeds easily to the not-intended part.
And of course, the second aspect, `the unequal coloration')happens from the same reason.

This paper clarifies long time our question about natural ai. We hope you enjoy above clarification.

Here is the movie of my twitter friend's. She is the professional dyer, and the movie shows how the Ryukyu ai change by 'oxidization' from green to blue ai color rapidly in the air.

http://ow.ly/P7CD

This page's is the original text written by Ichiro on 3th Jan 2010. This page can't be edited. Back to the editable pageThis site is hosted by ICHIROYA