DENIM PROCESSING

DEFINITIONS

• DENIM : A Firm 2/1 or 3/1 cotton twill-weave fabric with dyed blue warp and raw white weft. ( similar to yarn dyed fabric )

• Warp is dyed with indigo dyes .• Various dyeing methods, recipes, concentrations, the

reactions and oxidation time influences the effect and characteristics of the finishes

Basic Process line

Stone washed

Desized

Fabric is converted into garments

Sized Indigo-dye warp and raw white weft

Woven in a 2/1 or 3/1 twill weave

Garment process

DENIM PROCSSING

DRY PROCESS WET PROCESS

Scraping Sand blasting KMnO4 Spray Acid wash

Dry process

• Sand blasting : to produce localized abrasion

• Scraping : manual scraping using sand paper or grinding machine as per design

• KMnO4 Spraying : an alternative blasting technique

• Acid wash : use of thremocol ball and bleach in a single belly machine

Denim Wet processing

• Desizing : a process intended to remove size finish constituents from fabric before enzyme wash or bleaching

• Abrasion : a process which facilitates the indigo dye to be removed from the surface of the cotton fibre .

• Bleaching : a process intended to decolorize indigo by

using bleach liquor (NaOCl)• Softener wash : to improve the hand feel of the garment

by cationic or silicone softener

Chemicals and their uses

• Non ionic wetting agent : to increase the absorbency of the garments

• Lubricating agent : to avoid streak formation

• Amylase : an enzyme used to break down insoluble starch to soluble glucose ( 90 % of sizing material contains insoluble starch )

• Pumice stone : used during denim washing to get the grain effect ( replaced by enzyme to large extent )

Continued …

• Anti back staining agent : to avoid re deposition of the indigo dyes on the fabric surface

• Cellulase : an enzyme used to weaken the cotton fiber and hence increase abrasion

• NaOCl : Sodium hypochlorite used to lighten the shade of indigo

• Laccase : enzyme used to decolorize indigo ( by converting indigo into colorless compound called Isatin )

• Softeners : to improve hand feel and protect the denim from Ozone

Benefits of using enzymes

• Maximized fabric strength retention• Stone free processing • Fast processing • Improved wash look• No or less Garment damage • No machine damage• Easy handling and cost effective

Desizing

• MRL : 1: 5 to 1 : 10 • pH : 5 to 6.5 • Temp : 60 Deg C• Time : 20 min

• Chemicals ad dosage : • non ionic wetting agent ( 1 gpl )• Lubricating agent ( 0.5 gpl )• Anti back staining agent ( 0.5 to 1 gpl )• Amylase ( 0.5 to 1 gpl ) ( enzyme for breaking down starch

into soluble glucose )

Abrasion

• MRL : 1: 5 to 1 : 10 • pH : 6.5 • Temp : 55 Deg C• Time : 20 to 45 min

• Chemicals : • Anti back staining agent ( 0.5 gpl to 1 gpl )• Cellulase( 0.5 to 1 gpl )( enzyme for weakening cotton fiber

by converting the cellulase into glucose )

Bleaching

• MRL : 1: 5 to 1 : 10 • pH : neutral • Temp : Room Temp• Time : depends on the shade

• Chemicals : • NaOCl

Bio bleach

• MLR :1:5 to 1:10• pH : 4 to 5.5• Temp : 60 to 70 Deg C• Time :15 to 20 min

• Chemical used : – Laccase :1 gpl to 2 gpl

Special finishes

• Pigment spray

• Direct and reactive dye tinting

• Transfer printing

• Rubber feel

• Indigo retention

• Permanent crease

• Raw ( or undesized ) look