Caustic Wash Process on Garment

Define Caustic Wash:
Caustic wash is basically a preprinting wash. Caustic is a strong chemical with highly corrosive features. Prior to printing on cotton fabrics, grey goods are treated in boiling water with caustic, which also has strong cleaning power, especially for grease. This wash can remove all soil, dirt, grease, fine particles of cotton seeds as well as all foreign materials. As a result, only pure cotton fiber in the fabric for printing is left. This leads to stability of printing and a well cleaned fabric. However, when caustic wash is done on garments, just do the opposite of the above; fabric is not treated with caustic wash for cleaning prior to printing.

caustic washed t-shirt
Fig: Caustic washed t-shirt

Printing is done on the raw and unclean fabric so that about 30% of the printing done on the surface may eventually fade away. Finally, printed garments are caustic washed. This leads to about 30% of the printing washing away along with the foreign materials–leaving about 70% of the printing on the fabric. This makes the design or stripe of the desired look. For this type of wash, the printing must be pigment printed with a binder. Baking treatment should also be performed so that the color will stay on the fabric more or less securely to coincide with the caustic wash to be done later.

Purpose of Caustic Wash on Garment:

  1. Particular fading wash can be achieved.
  2. By caustic washing can remove dirt, dust, oil, impurities which is come from stitching and back process.
  3. It can improve the color fastness and rubbing fastness.
  4. It can increase hairiness of garments.
  5. It is increase the vintage or old looking appearance.
  6. Partially size material is removed more than normal or pigment wash.
  7. Good hand felling.
  8. It can increase comfort of garments.
  9. It can increase luster of fabric strength.

Caustic Wash Process on Garment:
Details of caustic wash on garment is described below:

A batch of 100kg pigment printed garments is considered. The garments are loaded in the garment washing machine together with 500 liters of water @ L:R = 1:5. Start machine running and the following chemicals add gradually in the liquor:

  • Caustic @ 4% = 4 kg
  • Soda ash @ 2% = 2 kg
  • Detergent @ 1% = 1 kg
  • H2O2 @ 4% = 4 kg
  • Stabilizer @ 2% = 2 kg

Start steam supply to raise liquor temperature to 70ºC and continue washing for 90 minutes. During this processing time, impurities and size material present in the garment is removed together with some portion of pigment. Hydrogen peroxide breaks down and produces per hydroxyl ions, which takes part in bleaching and reduces the color intensity of the pigment. As a result fading effect is produced in the garments. Presence of the stabilizer confirms the production per hydroxyle ions. When desired fading effect is produced in the garments, drop the liquor. Then again load 500 liter water in the machine and start machine running. Start steam supply to raise liquor temperature to 60ºC and continue processing for 10 minutes to remove adhering impurities from the garment fabric surface. Then drop the liquor.

To make the garments in neutral condition, load the machine with 500 liters water and 1 liter acetic acid @ 1%. Continue treatment for 5 minutes and drop the liquor. To increase surface feeling in the garments, again load 500 liters water and fabric softener @ 0.1% to 0.5%. continue treatment for 5 minutes and then drop the liquor. Unload the garments from the washing machine. Hydroextruct the garments and the dry the garments in the garments drying machine.

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