Causes of Fabric Shrinkage & How To Control The Shrinkage

Causes of Fabric Shrinkage

1. During spinning, weaving, dyeing and finishing, yarns and fibers are stretched and deformed under external force, generating internal stress within yarns, 
fibers and fabric structure. When the fabric is under static dry relaxation, static wet relaxation, dynamic wet relaxation or full relaxation,
the internal stress is released to varying degrees, allowing yarns and fibers to revert to their original state.

2. Fabrics made of different fibers have distinct shrinkage degrees, which mainly depend on fiber properties. Hydrophilic fibers such as cotton, linen and viscose feature high shrinkage, while hydrophobic synthetic fibers show low shrinkage.

3. Fibers swell when exposed to liquid, leading to an increase in fiber diameter. On fabric, this raises the curvature radius of fibers at interlacing points and shortens the overall fabric length. For instance, cotton fibers expand by 40% to 50% in cross-sectional area and 1% to 2% in length after absorbing water. Synthetic fibers are prone to heat shrinkage, generally around 5% in boiling water.

4. When exposed to heat, fibers change in shape and size and shrink permanently after cooling, which is defined as thermal shrinkage. The thermal shrinkage rate refers to the percentage of length change before and after heating. Common test methods include boiling water test at 100°C, hot air test and steam test at temperatures above 100°C. Results vary with fiber structure, heating temperature and duration. Typical values: polyester staple fiber 1% boiling water shrinkage, vinylon 5% boiling water shrinkage, chlorofiber 50% hot air shrinkage. Fiber thermal shrinkage is closely linked to fabric dimensional stability and provides references for subsequent production processes.

Fabric Shrinkage Rate Test Methods

Washing and dry steaming are the mainstream testing methods for fabric shrinkage. The standard washing test procedures are as follows:

1. Sampling: Take samples from the same batch at least 5 meters away from the fabric edge. Exclude fabrics with defects that may affect test results. Prepare square samples of 70–80 cm in width suitable for washing. Lay samples flat naturally for 3 hours, then mark a 50 cm × 50 cm test area at the center with a marker.

2. Marking: Place the sample on a flat surface and smooth out creases gently without stretching. Avoid excessive force during marking to prevent position deviation.

3. Washing treatment: Sew along the marked lines to prevent ink fading after washing. Use double stitching for knitted fabrics and single stitching for woven fabrics. For knitted fabrics, sew two warp sides and one weft side; for regular woven fabrics, sew all four sides with proper stitch tension. Overlock all four edges for thick fabrics or loose-weave materials. Immerse the sewn sample in 30°C warm water, wash in a washing machine, then tumble dry or air dry. Cool down thoroughly for 30 minutes before measurement.

4. Calculation: Shrinkage Rate = (Original Size − Size after Washing) ÷ Original Size × 100% Both warp and weft shrinkage rates shall be measured.

Shrinkage Rate of Different Fabrics

In general order from the lowest to the highest shrinkage rate: synthetic fibers & blended fabrics, wool fabrics, linen fabrics, cotton fabrics, silk fabrics, viscose fiber, artificial cotton and artificial wool fabrics.

Standard shrinkage rate range for common fabrics:

· Cotton: 4%–10%

· Chemical fiber: 4%–8%

· Cotton-polyester blend: 3.5%–5.5%

· Grey cotton cloth: 3%

· Indigo denim: 3%–4%

· Poplin: 3%–4.5%

· Printed cloth: 3%–3.5%

· Twill fabric: 4%

· Workwear denim: 10%

· Artificial cotton: 10%

Factors Affecting Shrinkage Rate

1. Raw materials: Fibers with high moisture absorption expand significantly after soaking and have a higher shrinkage rate. For example, the moisture absorption rate of some viscose fibers reaches 13%, while synthetic fibers with low hygroscopicity show minor shrinkage.

2. Fabric density: Similar warp and weft density leads to close shrinkage rates in both directions. Fabrics with higher warp density have larger warp shrinkage, and those with higher weft density have larger weft shrinkage.

3. Yarn count: Fabrics made of thick yarns have higher shrinkage rates than those with fine yarns.

4. Production technology: Fabrics subjected to repeated stretching, long processing time and high tension during weaving, dyeing and finishing tend to shrink more.

5. Fiber composition: Natural plant fibers (cotton, linen) and regenerated cellulose fibers (viscose) absorb moisture and swell easily, resulting in high shrinkage. Wool fibers are likely to felt due to the scale structure on fiber surface, impairing dimensional stability.

6. Fabric structure: Woven fabrics have better dimensional stability than knitted fabrics; high-density fabrics outperform low-density ones. Among woven fabrics, plain weave shrinks less than flannel. Among knitted fabrics, plain stitch has lower shrinkage than rib stitch.

Fabrics are inevitably stretched during dyeing, printing and finishing, resulting in residual tension. The tension is released once the fabric gets wet and causes shrinkage. Preshrinking finishing is widely adopted in actual production to solve this problem.

Washing & maintenance: Washing, drying and ironing all affect fabric shrinkage. Hand-washed samples show better dimensional stability than machine-washed ones. Higher water temperature usually leads to poorer stability.

Drying methods also exert great influence: drip drying causes the least dimensional change, tumble drying the most, and flat drying on metal mesh & line hanging are in between.

Appropriate ironing temperature helps reduce shrinkage. High-temperature ironing works well for cotton and linen fabrics. However, excessive heat will damage synthetic fibers, making the fabric stiff and brittle.