Notes on Reactive Dye
Last updated on May 30th, 2026 at 08:03 pm
Reactive dyes are special coloring agents that textile industries use for dyeing fibre, yarn, fabrics, and garments. These dyes are popular in the textile industry because they make colors that fix well and don’t fade quickly. Unlike other dyes that fix on the fabric’s surface, reactive dyes combine with the fabric’s molecules through a chemical reaction. It makes the colors they create stay firm even after you wash them many times.
Stripping Process of Reactive Dyed Fabric
Stripping
Stripping becomes necessary when uneven dyeing occurs. By stripping azo groups (-N=N-) of the dye, it is removed. There are two methods of stripping, such as
- Partial stripping method.
- Full stripping method.
Partial Stripping Method
Partial stripping is obtained by treating the dyed fabric with dilute acetic acid or formic acid. The recommended concentration is between 5 to 10 ml glacial acid or 2.5 – 10 parts of formic acid (85%) per 1000 parts of water.
Recipe:
| Glacial acetic acid: | 5 – 10 gm/L |
| Time: | 20 – 30 mins. |
| Temperature: | 85°C – 90°C |
Full Stripping
For complete stripping, the goods are firstly treated with Sodium hydrosulphite (Na2S2O4) at boil. Then washed off and bleached at ordinary atmospheric temperature in a liquor containing 1 part per 100 of commercial sodium hypochlorite.
Recipe:
| Na₂S₂O₄: | 5 gm/L |
| Na₂CO₃: | 2 gm/L |
| Boiling: | 20 – 30 mins. |
| Time: | 20 – 30 mins. |
| Temperature: | Boiling |
Functions of Different Chemicals used in Reactive Dye
Salt
Salt acts as an electrolytic material. It helps to absorb the dye particle.
Soda Ash
Soda ash acts as an alkali medium, and it also acts as a fixing agent.
Urea
It will give deeper shade in the dyeing bath. A small amount of urea will give light shade. To solubilize the dye stuff properly, urea is used.
Sodium Alginate
It is a thickening agent. It is collected from seaweeds. It helps to bind the dye materials in their position. It will also act as a fixing agent
Why Soaping is Necessary After Dyeing
We use different types of dyes in the dye bath. Maximum cases of dye stuffs are sedimented on the bottom of the dye bath and deposited on the textile material. We use the soaping method to increase the brightness and to remove the floated color; we use the soaping process.
Salt & soda ash used in reactive dyes for shades
| Shade | Salt (g/l) | Soda Ash (g/l) |
| Light Shade | 37 | 12 |
| Medium Shade | 60 | 15 |
| Dark Shade | 80 | 20 |
Application of Reactive Dyes on Cotton Goods
Now a day reactive dyes are popularly used for cotton goods. Generally 4 types of cotton goods are used to dye with the reactive dye:
- Loose fiber form.
- Yarn form.
- Knit goods
- Woven fabric.
Jigger dyeing m/c (Woven fabric), Winch dyeing m/c (Knitted fabric) and Jet dyeing m/c (Knitted + Woven)
Test Method of Reactive Dye
Recipe:
| H₂SO₄: | 1 cc/litre of water |
| Na₂S₂O₄: | 2 cc/litre of water |
| M : L | 1:20 |
| Temperature: | Up to boiling |
| Time: | 30 mins. |
When a sample of reactive-dyed fabric is treated in a test tube containing 1 cc of H₂SO₄ per 1 liter of water, it results in the bleaching of reactive color from the dyed fabrics. It is one of the identification tests of reactive color.
The reactive color remains fixed on the textile material, though it is treated or boiled with pyridine or chloroform. On the other hand, textile material dyed with direct, azoic etc. dye stuffs and treated with above chemicals then color will come out easily. It is one of the identification tests of reactive color.
The second one is one of the most efficient test methods of reactive dye.
Classification of Reactive Dye with Example
On the basis of reactive group: Two types:
- Halogen added group (Cl2, F2, Br2,I2), Example: Pyrimidine.
- Vinyl-added group (– CH = CH₂) (– D – SO₂ – NH – CH = CH₂) [– CH = CH₂ ………. Reactive group], Example: Levafix.
On the basis of reactivity: Three types.
- High reactivity. Ex. Procion-E. {Medium alkali (NaHCO₃) used}.
- Moderate reactivity. Ex. Livafix – E. {Medium alkali (Na₂CO₃) used}
- Low reactivity. Ex. Premazine: {Strong alkali (NaOH) is used}.
On the basis of use: Two types;
- Cold brand reactive dyes (High reactivity): 40°C – 50°C
- Hot brand reactive dyes (Low reactivity): 90°C – 95°C
Use of Hot brand is maximum in our country, Cold brand is used for batik, tie dye etc.
Reactive Dyeing Methods
Batch dyeing method (discontinuous method):
- Hot brand dye.
- Cold brand dye.
Continuous method:
- Pad system method.
- Pad thermo-fixation method.
Semi-continuous method:
- Pad roll method
- Pad – jigger method.
Description of Cold Brand Dyeing with Reactive Dye
Recipe:
| Dye stuff: | 3% (According to the wt. of mlts) |
| Soda Ash: | 15 gm/L |
| H2O: | 10 times |
| Temperature: | 40°C |
| Salt: | 60 gm/L |
| Time: | 1 Hour |
Dyeing Scheme
Working Procedure
At first, solubilize the dyestuff with a little amount of cold water. Take required water to the dye bath. Dye liquor and salt are given to the dye bath and stirred thoroughly. Then the textile material is taken to the dye bath and dyed for 20–30 mins. After dyeing, the material is rinsed with cold water. Then it is treated with a 20% soap and 1% soda solution in a bath for 30 minutes, and then the material is washed and dried.
Cotton Dyeing with Reactive Dyes (Hot Brand)
Recipe:
| Dye stuff: | 1 – 3% (According to the wt. of mtls) |
| Salt: | 30 – 60 gm/L |
| Soda Ash (Na₂CO₃): | 15 gm/L |
| Water: | 20 times |
| Temperature: | 90°C – 100°C |
| Time: | 1.5 – 2 Hours |
Working Procedure
When soda ash is used as fixing agent the temperature should not be below 80ᵒC. In case of turquoise blue, the temperature should be raised to 90°C–95°C while fixing. After dyeing, the material was lifted from the bath, squeezed, rinsed well in water, soaped at boiling temperature for 30 minutes, and then rinsed and dried.
| Shade | Salt Addition |
| Light Shade | 40 – 50 gm/L |
| Medium Shade | 60 – 75 gm/L |
| Dark Shade | 80 – 100 gm/L |
Notes:
- Salt is used for the sustainment of color on fiber.
- Soda ash is used only for the permanency of color.
Pad-steam method of Reactive Dye
Recipe (For medium shade):
| Dye stuff: | 10 – 20 gm/L |
| Soda Ash: | 5 – 10 gm/L |
| Common salt: | 60 – 80 gm/L |
| Urea: | 150 gm/L |
| Sodium Alginate: | Little amount |
Sequence of Operation
Working Procedure
In this method fabric is dyed in large scale. Two bowls are used here. In the first, padding is done on the fabric with urea & dye solution at 60°C – 80°C temperature. Urea is used to dissolve the dye stuff and to penetrate into the fabric. Na-alginate is used as a migration inhibitor. Then the fabric is passed through the drying chamber, & again padding is done with NaOH at 60°C temperature. Then steaming is done at 100°C – 102°C for 30 – 60 seconds. Then after rinsing & soaping, fabric is washed & dried.
Pad Thermo – Fixation Method of Reactive Dye
Recipe:
| Dye stuff: | 2% (According to the wt. of mtl) |
| Soda Ash: | 1% |
| Salt: | 8% |
| Urea: | 15% |
| Sodium Alginate: | Little amount |
Working Procedure
In this method padding bath continuously dye, alkali, salt, urea and Na – Alginate liquor. Padding is done in the bath at room temperature. Then the fabric is passed through the drying chamber. Then thermofixation is done at 160°C for 5 minutes. Finally, rinsing, soaping, and again rinsing are done. This method is suitable for moderately reactive dyes.
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