This document provides information on dyeing fabrics with vat dyes, including recipes for different dye concentrations and oxidation methods. It examines the color fastness of knit and woven cotton samples dyed with 1% or 2% vat dye to washing, water, rubbing, and light using various oxidizing agents like hydrogen peroxide, sodium perborate, and potassium dichromate. Test results show color fastness ratings mostly between 3-5. The document also analyzes the costs and risks of different oxidation methods and discusses common industrial practices for improving color fastness through air oxidation and surface coatings.

1. DYEING WITH VAT DYEDYEING WITH VAT DYE
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2. RECIPE OF EACH (10GM) KNIT & WOVEN SAMPLE
 DYESTUFF:
Option 1: Vat dye, Blue color : 1% on the weight of fabric
Option 2: Vat dye, Blue color : 2% on the weight of fabric
Option 3: Vat dye, Yellow color : 1% on the weight of fabric
Option 4: Vat dye, Yellow color : 2% on the weight of fabric
 CHEMICALS & AUXILIARIES:
NaOH : 7% on the weight of fabric
Hydrose : 6% on the weight of fabric
Salt (NaCl) : 10% on the weight of fabric
Wetting agent (1% stock soln
) : 1 g/l
Sequestering agent (1% stock soln
) : 1 g/l
Water : Required amount as calculated below
 DYEING PARAMETER:
pH : 12
M:L : 1:30
Temperature x Time : 70˚C x 45 min
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3. DYEING CURVE
33

4. OXIDATION AND AFTER TREATMENT
 OXIDATION RECIPE
When Air oxidation = No mentionable amount as available in environment
When H2O2 = 2 gm/l
When Na-perborate = 2 gm/l
When K2Cr2O7 = 2 gm/l
M:L = 1:30
Temperature = 60˚C
Time = 20 min
 SOAPING RECIPE:
Detergent = 2gm / l
M:L = 1:30
Temperature = 60˚C
Time = 15 min
 NEUTRALIZATION:
Rinsing with 1ml/l acetic acid at 60°C temperature for 10 min.
Then wash the fabric with cold water
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5. OXIDATION AND AFTER TREATMENT CURVE
55

6. 66

7. COLOR FASTNESS TO WASH
Shade Fabric type Oxidation with
Color fastness to Washing
Color changing Color staining
2%, blue Knit
H2O2 4 4-5
Na-Perborate 3-4 4-5
Air 4 4-5
K2Cr2O7 3 4-5
2%, blue Woven
H2O2 4 4-5
Na-Perborate 3-4 4-5
Air 4 4-5
K2Cr2O7 3-4 4-5
2%, yellow Knit
H2O2 4-5 4-5
Na-Perborate 4 4-5
Air 4-5 4-5
K2Cr2O7 3-4 4-5
2%, yellow Woven
H2O2 4-5 4-5
Na-Perborate 3-4 4-5
Air 4 4-5
K2Cr2O7 3-4 4-5
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8. RESULT ANALYSIS OF COLOR FASTNESS TO WASH
88

9. COLOR FASTNESS TO WATER
99
Shade Fabric type Oxidation with
Color fastness to water
Color changing Color staining
2%, blue Knit
H2O2 4 4-5
Na-Perborate 3-4 4-5
Air 4 4-5
K2Cr2O7 3-4 4-5
2%, blue Woven
H2O2 4 4-5
Na-Perborate 3-4 4-5
Air 4 4-5
K2Cr2O7 3-4 4-5
2%, yellow Knit
H2O2 4-5 4-5
Na-Perborate 4 4-5
Air 4 4-5
K2Cr2O7 3-4 4-5
2%, yellow Woven
H2O2 4-5 4-5
Na-Perborate 3-4 4-5
Air 4-5 4-5
K2Cr2O7 3-4 4-5

10. RESULT ANALYSIS OF COLOR FASTNESS TO WATER
1010

11. COLOR FASTNESS TO RUBBING
1111
Shade Fabric type Oxidation with
Color fastness to Rubbing
Dry rubbing Wet rubbing
2%, blue Knit
H2O2 4-5 3-4
Na-Perborate 4-5 2-3
Air 4-5 3
K2Cr2O7 4 2
2%, blue Woven
H2O2 4-5 3-4
Na-Perborate 4-5 2-3
Air 4-5 3
K2Cr2O7 4 2
2%, yellow Knit
H2O2 4-5 3-4
Na-Perborate 4-5 2-3
Air 4-5 3
K2Cr2O7 4 2
2%, yellow Woven
H2O2 4-5 3-4
Na-Perborate 4-5 2-3
Air 4-5 3
K2Cr2O7 4 2

12. RESULT ANALYSIS OF COLOR FASTNESS TO RUBBING
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13. COLOR FASTNESS TO LIGHT
1313
Shade Fabric type Oxidation with Color fastness to light
Color changing
2%, blue Knit
H2O2 4
Na-Perborate 4
Air 4
K2Cr2O7 4
2%, blue Woven
H2O2 4
Na-Perborate 4
Air 4
K2Cr2O7 4
2%, yellow Knit
H2O2 4
Na-Perborate 4
Air 4
K2Cr2O7 4
2%, yellow Woven
H2O2 4
Na-Perborate 4
Air 4
K2Cr2O7 4

14. RESULT ANALYSIS OF COLOR FASTNESS TO LIGHT
1414

15. 1515

16. COST ANALYSIS
1616
Chemicals used in oxidation Current Market Price (Tk) / per Kg
Air Free at environment
H2O2
26
Na-perborate 2500
K2Cr2O7
5000
Chemicals used in oxidation
Cost in our processing (Tk)
for each 10gm sample
Cost of processing
(Tk)
of 1Kg fabric
Air 0 0
2 g/l H2O2 (0.6x26)/1000 = 0.0156 1.56
2g/l Na-perborate (0.6x2500)/1000 = 1.5 150
2g/l K2Cr2O7 (0.6x5000)/1000 = 3 300

17. COST OF OXIDATION OF 1 KG FABRICCOST OF OXIDATION OF 1 KG FABRIC
1717

18. DECISIONDECISION
1818

19. COLOR FASTNESS
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20. COST ANALYSIS
2020

21. SHADE ANALYSIS
2121

22. RISK FACTOR ANALYSISRISK FACTOR ANALYSIS
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23. OXIDATION PRACTICE IN INDUSTRIES
 Air oxidation as most economicAir oxidation as most economic
 Then treatment with fixer to make a surface coating to improve rubbingThen treatment with fixer to make a surface coating to improve rubbing
fastnessfastness
 Earlier fixer was formaldehyde or melamine based resin but it’s nowEarlier fixer was formaldehyde or melamine based resin but it’s now
banned according to REACH protocolbanned according to REACH protocol
 Now a days formaldehyde free resin like silicon based or polyamide basedNow a days formaldehyde free resin like silicon based or polyamide based
fixer are usedfixer are used
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