colorant
Leuco-indigo (reduced indigo, "indigo white")
Also known as: leuco-indigo, indigo-white
The water-soluble, pale yellow to yellow-green form of indigo obtained by reduction. On contact with air it oxidises back to insoluble blue indigo. In the vat, this is the form in which the dye enters the cloth.
Theme: Dissolve, then return
Claims and evidence (5)
The limitations noted for some sources are recorded in Japanese only — see the Japanese edition.
Leuco-indigo (reduced indigo, "indigo white") is soluble in watercontextual
States that because this vat dye does not dissolve in water, it must first be converted, by reduction, into its soluble form, leuco-indigo, before it can serve as a textile dye.
Source: The Mechanism Underlying of Long-Term Stable Indigo Reduction State in Indigo Fermentation Using Sukumo (Composted Polygonum tinctorium Leaves) （Zhihao Tu; Helena de Fátima Silva Lopes; Takashi Narihiro; Isao Yumoto, 2021） ・Introduction、冒頭（"Indigo is one of the oldest dyes..."の段落） ・textbook ・ checked against the source by AI
textbook ・ 
checked against the source by AIDescribes the vat (built from the doro-ai) on its fourth day as having a greenish tinge just below the surface, said to be evidence that plenty of the dye "leuco-indigo" (ロイコインディゴ) has formed, implying it is present in dissolved form.
Source: 泥藍を作ろう（畑だより 2021年09月23日） （藍ばたけ（琉球藍染め）, 2021） ・本文末尾「＜藍建てメモ＞」に続く追記、藍建て4日目の描写 ・practitioner's record ・ checked against the source by AI
practitioner's record ・ Leuco-indigo (reduced indigo, "indigo white") differs from Indigo (indigotin)contextual
Explains that indigo is reduced, taken up by cloth or thread, and then on oxidation reverts to indigo, dyeing it blue.
Source: 連載〈阿波藍5〉染料液の作り方（藍を建てる） （川人美洋子, 2010） ・P-284, 「藍を建てる」の段落 ・practitioner's record ・ checked against the source by AI
Captions a diagram stating that indigo is transformed into leucoindigo by the action of indigo-reducing bacteria.
Source: Microbial Communities Associated With Indigo Fermentation That Thrive in Anaerobic Alkaline Environments （Keiichi Aino; Kikue Hirota; Takahiro Okamoto; Zhihao Tu; Hidetoshi Matsuyama; Isao Yumoto, 2018） ・Figure 1 のキャプション ・textbook ・ checked against the source by AI
Leuco-indigo (reduced indigo, "indigo white") ・property ― pHcontextual
Scope: Indigo dyeing of cotton, as cited in the source
States that substantivity for cotton significantly increases as dyebath pH is reduced from highly alkaline 13.5 to moderately alkaline 10.5, but that pH must always remain above 9.9 to keep the indigo in its soluble leuco-indigo form; the optimum pH is around 11, where the fraction of the monophenolic form is greatest.
Source: Indigo （David Richardson; Sue Richardson, 2016） ・"Ring Dyeing and Substantivity" 節 ・textbook ・ checked against the source by AI
Pre-Reduced Indigo Crystals is a type of Leuco-indigo (reduced indigo, "indigo white")contextual
Scope: Dharma Pre-Reduced Indigo Crystals
Describes the product as synthetic indigo (chemically identical to natural indigo) that has been chemically pre-reduced then dried, which lets the milder soda ash replace lye.
Source: Pre-Reduced Indigo Crystals (product page, Description + Instructions tabs) （Dharma Trading Co.） ・Descriptionタブ、"As an alternative, try this Pre-reduced Indigo"の段落 ・manufacturer statement ・ checked against the source by AI
manufacturer statement ・ States this specially formulated indigo is already 60% reduced so soda ash can be used, there is no need to grind and paste the granules since they dissolve easily, and the vat can be ready in about 10 minutes.
Source: Pre-Reduced Indigo Instructions （Dharma Trading Co.） ・記事冒頭の段落 ・manufacturer statement ・ checked against the source by AI
Natural Indigo Concentrate is a type of Leuco-indigo (reduced indigo, "indigo white")contextual
Scope: Natural Indigo Concentrate
Describes the product as a high-concentration indigo liquid made by reducing and dissolving natural Indian indigo, which can be diluted to the desired strength simply by mixing with water containing the attached sodium hydrosulfite.
Source: 天然藍濃縮液（商品同梱の説明書、PDF） （株式会社田中直染料店） ・P1、商品説明本文 ・manufacturer statement ・ checked against the source by AI