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Page 92 - Shawl Weaving Artisan - TP
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    9  Then prepare a new bath with clean water and add a   12 Gently squeeze out excess water without wringing
              small amount of acetic acid to adjust the pH to 6-7.  (wringing can damage wool fibers).
           10 Soak the yarn in this neutralizing bath for 15 minutes.  13 Lay the yarn flat or hang it in a shaded, well-ventilated
                                                                   area to air dry.
           11 Rinse the yarn again with clean water to remove any
              remaining chemicals.

           TASK 2: Bleaching of cotton yarn with sodium chlorite

           1  Heat water to 90–95°C in a container.             8  Heat the solution to 80–90°C and keep the yarn in it
           2  Add caustic soda (NaOH) in it.                       for 1–2 hours.
                                                                9  Stir occasionally to ensure uniform bleaching.
           3  Then add 1–2 g/l, detergent in a solution.
                                                                10 Then check the yarn for the desired whiteness level.
           4  Soak the cotton  yarn in this solution for 45–60     If achieved, move to the next step.
              minutes and stir gently.
           5  Rinse well with warm water to remove all chemicals.  11 Drain the bleaching  bath  and rinse the yarn with
                                                                   Luke warm water.
           6  Then prepare a bleaching bath:
                                                                12 Then prepare a neutralizing bath:
              •  Fill a clean container with warm water 70–80°C.
                                                                   •  Add 1–2 g/L sodium bisulfite (NaHSO ) to fresh
              •  Then add sodium chlorite (NaClO ), 3–5 g/l and       water.                            3
                                               2
                stir well.
                                                                   •  Soak the yarn in  this bath for 15 minutes  to
              •  Now add the formic acid for adjusting the pH to      remove chlorine dioxide residues.
                3.5–4.5.
                                                                13 Rinse again with clean water.
           7  Then  immerse the scoured cotton yarn in the      14 Gently squeeze out excess water (do not wring).
              bleaching bath.
                                                                15 Air-dry in a shaded, well-ventilated area to avoid
                                                                   fiber damage.

           80             Textile & Handloom : Shawl Weaving Artisan (NSQF - 2024) Exercise 1.6.54

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