Shrinkage Rate

Shrinkage rate measures the percentage by which fabric contracts in length and width after washing, drying, or other processing. This specification is essential for product development and quality control, as excessive shrinkage can render finished products unusable or require oversizing during manufacturing to compensate.

Greige fabric shrinkage and GSM considerations before finishing

Before wet processing or finishing loom-state greige fabric, mills and converters must calculate the direct interaction between dimensional shrinkage and finished cloth weight (GSM).

When fabric shrinks during wet processing or stenter heat-setting, its total surface area contracts while yarn mass remains largely unchanged. Consequently, the fabric's areal density increases:

$\text{Finished GSM} = \frac{\text{Greige GSM}}{(1 - S_L) \times (1 - S_W)}$

Where:

• $S_L$ = length (warp) shrinkage expressed as a decimal (e.g. $4\% = 0.04$)
• $S_W$ = width (weft) shrinkage expressed as a decimal (e.g. $6\% = 0.06$)

Finished GSM calculation table (Initial Greige GSM = 150)

(Note: Actual finished GSM will also reflect slight mass reductions from desizing/scouring or mass increases from chemical coatings and print pastes).

Reverse calculation: target finished GSM to required greige GSM

When issuing a weaving order to achieve an exact finished contract weight after dyeing:

$\text{Required Greige GSM} = \text{Target Finished GSM} \times (1 - S_L) \times (1 - S_W)$

Example: If target finished GSM is 180 GSM, with anticipated $4\%$ length take-up and $6\%$ width stenter contraction: $\text{Greige GSM} = 180 \times 0.96 \times 0.94 \approx \mathbf{162.4 \text{ GSM}}$

Testing follows a multi-standard procedure. Mark precise dimensions on the fabric before washing, launder according to ISO 6330 (domestic washing procedure — water temperature, agitation, detergent dosage), dry according to the specified method, then measure the dimensions again under ISO 5077 (the actual dimensional-change measurement method). For commercial specifications, the equivalent U.S. pair is AATCC 135 (home laundering) and the measurement step under AATCC method TM 135 / AATCC 150 (commercial laundering). The shrinkage rate is calculated as:

Shrinkage (%) = (Original Dimension − Final Dimension) ÷ (Original Dimension) × 100%

Warp (length) and weft (width) directions are measured and reported separately, as polyester shrinkage often differs between them due to differential yarn crimp and stenter overfeed.

Multiple factors influence shrinkage behavior. Natural fibers generally shrink more than synthetics because their structure absorbs water and releases tension introduced during weaving. Yarn twist affects shrinkage—higher twist creates more stored tension that releases during washing. Fabric construction plays a role, with tighter weaves typically showing less shrinkage. Finishing treatments can dramatically reduce shrinkage; sanforizing, a mechanical pre-shrinking process, brings cotton shrinkage below 1%. Washing conditions matter too—hot water and aggressive agitation increase shrinkage compared to gentle cold washing.

Industry standards typically require shrinkage below 3% for bedding and apparel, with premium products held to below 1%. When specifying fabric width, buyers should account for expected shrinkage during finishing to ensure the final product meets dimensional requirements. For fabrics sold by weight (GSM), note that shrinkage increases GSM since the same mass occupies a smaller area after shrinking.