Basic Dyeing Solution


Sequence in dyeing factory
1.     Lab- dip preparation.
2.     Lab-dip sending to the buyer.
3.     Order place for bulk production.
4.     Raw material preparation.
5.     Dyeing.
6.     Washing-off.
7.     Softening.
8.     Finishing.

Redyeing: If the shade is not match with the lab-dip, then redyeing is done.
·        Stripping: Remove the color from the dyed fabric and make the fabric is white by adding Hydrose, Caustic Soda (NaOH),H2O2 is called Stripping
·        Topping: After removing the previous water from the dyeing machine, redyeing the fabric with new dyes, chemicals and water is called topping.
·        Addition: Adding the color into the dye bath (running dye bath) is called addition. This is done, when shade is not matching or required to light shade to deep shade.
Bi-carbonate content:
Na (HCO3) ===== (heat) ====Na2CO3+CO2+H2O
1.     Change Ph (alkali condition).
2.     Shade variation in dyeing.
3.     Loss of shade and dye.
What happened if alkali is added before alkali fixation?
1.     Premature fixation before migration.
2.     Loss of migration potential.
3.     Increased hydrolyzed dye to wash-off.
4.     Loss of shade reproducibility.
·        Exhaustion: The amount of dye exhaust into fibres under alkali condition or alkali addition.
·        Substantivity: The amount of dye exhaust into fibres before alkali addition or neutral condition.
·        Fixation: The amount of dyes reacts with the fibres after adding alkali.
·        Affinity: Tendency of a dye to move from dye bath into a substance.
·        Reproducibility of Shades:
The shade of the dyes should be reproducible when required. Certain dyes have ability to overcome the factors like liquor ratio, pH, temperature etc. which affect the reproducibility


 Dyeing possibilities of blends:
1.     Union dyeing: Same shade and tone.
2.     Reverse dyeing: Only one part of the fabric is dyed (For P/C fabric).
3.     Cross dyeing:
4.     Shadow effect: Same hue and tone but shade% is different.
5.     Contrast effect: Different hue and tone and different shade%.
Color fastness: Resistance of color in a dyed or printed textile material against various types of influences like water, air, light, rubbing etc.
Some color fastness:
·        Wash fastness.
·        Light fastness.
·        Perspiration fastness.
·        Sea water fastness.
·        Rubbing fastness.



Dyes and dyeing conditions:
Dyes 
Dyeing Condition (pH)
Reactive
              7.0 (Exhaustion)
               11.0 (Fixing)
Acid(Wool)
Acid
            2-4, 4-6, 6-8 (depends                                         on types of dyes)
Basic
                          3.5-4
Direct
                          7.0
Sulphur

Vat

Disperse
                           5-6



Surface tension: In a liquid each molecules are attached by the neighboring molecules from all direction and remain stationary. But the molecules on the top line of surface are only attached by left and right side molecules. Upper surface has no molecules. As a result a pull down effect acts on the surface and surface become convex. This phenomenon of liquid is called surface tension.

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