Vat Blue 1 (Indigo blue) is blue powder. It is insoluble in water and alcohol; soluble in aniline solution (hot). It is yellow green in concentrated sulfuric acid, blue precipitate after dilution. Red yellow blush is formed in concentrated nitric acid. Heating to 170 ° C into a purple-red gas, sublimation phenomenon, but does not decompose; in the enclosure, dry distillation, decomposition into aniline. The leuco body formed by the dye in the alkaline powder solution is light yellow, in the acid insurance powder solution white.
TRADE NAME:Indigo blue,Vat Indigo,Indigo
Dyeing depth g/L | 30 |
Dyeing method | IN |
Leuco color | Blue |
Leveling property | ▲▲ |
Dead cotton | △ |
Light (Xenon test 1/12) | 6-7 |
Light (Xenon test 1/1) | 7-8 |
Light (Xenon test 2/1) | 7-8 |
Dyeing method | Dyeing temperatuer (℃) | Reduction method | Reduction temperature (℃) | Leveling Property | other Properties |
C | 20~25 | Dry Cylinder | 50~60 | medium | Very low affinity |
light fastness | soapping(95℃) | Perspiration | Rubbing | Ironing | Bleaching resistant | Merceized | |||||||
standard depth | 1/12 depth | orginal color changed | white fabric stained | orginal color changed | white fabric stained | Dry | Wet | immediatly | 4hafter | chlorine bleaching | Oxygen bleaching | orginal color changed | white fabric stained |
3~4 | — | 2 | 4 | — | — | 1~2 | 1 | — | 5 | 2 | — | 4~5 | — |
Vat Blue 1 Mainly also be used for wool and silk carpets and handicrafts in the application. Pure product is used in food dyes, can also be processed into organic pigments.
1.Vat Blue 1(Indigo blue) is mainly used for dyeing cotton yarn or cotton cloth, such as soil cloth, flower cloth, wool blue cloth in rural and remote minority areas, as well as cloth for denim clothing popular at home and abroad. Most of them are dyed by indigo and then interwoven with white yarn. Indigo is used for dyeing cotton yarn or cotton cloth. According to the reducing agent and alkali agent used, there are four kinds of fermentation method, insurance powder method, zinc powder lime method and ferrous sulfate method. Currently, the insurance powder method is commonly used.
2. When indigo blue is dyed by the insurance powder method, it is reduced by dry cylinder, the reduction temperature is 50~60°C, and the dry cylinder stabilization time is 30min.
3. Indigo leuco body has very low affinity for cotton fiber, generally low temperature dyeing. Because low temperature dyeing dye is not easy to penetrate, the concentration of dyeing liquid is too high, which will cause a lot of floating color, so that the dye is not resistant to friction, so multiple times of dip dyeing is used. For each dipping, it needs to be oxidized and then do the second dipping. If it is light, it needs to be dyed two or three times, the middle color is about five times, and the dark color is up to eight or nine times, so the yield is very low. The machine has been widely used in the dyeing of indigo yarn, which greatly improves the production efficiency.
Vat Blue 1 should be stored in a cool, dry, ventilated place, pay attention to fire and moisture.
Vat Blue 1 is insoluble as supplied. In the dyehouse it is reduced under strongly alkaline conditions (commonly using sodium hydrosulphite + caustic soda or controlled electrochemical reduction) to produce the water-soluble leuco form. Fibres are dipped while the dye is in leuco form; exposure to air oxidizes the dye back to its insoluble blue state on the fibre, locking in excellent fastness.
For consistent shade and penetration, use a freshly prepared sodium hydrosulphite + NaOH bath at pH ~11–12 and temperature 20–40°C depending on procedure (lower temp for leveling, higher temp for faster penetration). Control dissolved oxygen and liquor ratio: multiple short dips in a stronger leuco bath produce smoother denim tone and better crocking control than a single deep dip.
Reduce crocking by adopting: (1) multiple lighter dips instead of one heavy dip, (2) an optimized oxidation step (gentle exposure rather than harsh aeration), (3) after-treatments such as resin crosslinking or silicone finishing to improve surface fixation, and (4) enzyme or polishing finishes that remove loosely bound particles. Lab test with Wyzenbeek or crockmeter before scale-up.
Vat Blue 1 performs best on cellulose fibres (cotton, viscose). It can be used on some protein fibres (wool, silk) and blended substrates but requires process optimization; on wool/silk, use milder alkaline conditions and lower temperatures to avoid fibre damage.
Because the dyeing process uses reducing agents and caustic, effluent contains residual reducing salts and high pH. Best practice: neutralize pH, remove excess reducing agent (air oxidation or chemical dosing), and use biological or advanced oxidation treatments for organic load. Recover and reuse washwaters and minimize sodium hydrosulphite overdosing to reduce sulfite discharge.
Store in original sealed bags or containers in a dry, ventilated area away from strong oxidizers and heat. Use dust control and PPE — N95 or filtered respirator when handling powder, safety goggles and gloves. Keep SDS accessible and follow local transport/packaging regulations.
Denim shade is process dependent, but typical yarn dyeing uses repeated low-depth dips (e.g., 0.5–1.5% owf per dip with 6–12 dips depending on target depth and bath concentration). For piece dyeing aim for controlled multiple immersions rather than one high-concentration immersion to get classic indigo ring and fading behavior.
