Thermal Shrinkage

Definition and Overview

Thermal shrinkage refers to the property of a material in which fibers or structure contract when heat is applied, or to the resulting shrinkage. In the process of fusing interlining, the difference in thermal shrinkage between the shell fabric and the interlining affects the finished result.

In the interlining field, it generally means dimensional change that occurs during fusing press rather than intentionally shrinking the material with heat to shape it. It differs from shrinkage caused by moisture such as washing, both in the factors that cause it and in how it is checked.

Parts Used and Their Role

Fusible interlining is used in areas where shape retention is needed, such as the front body, facing, collar, collar stand, cuffs, belt, and pocket opening. In these areas, differences in thermal shrinkage can cause surface wrinkles, pulling, and puckering, so stable fusing is important.

Especially in areas such as collars and front edges, where straightness, left-right symmetry, and a natural roll are required, even a slight difference in shrinkage can easily show on the appearance. Check the dimensions and feel after fusing, not only before cutting.

• Shape-retaining areas such as collars, collar stands, and cuffs
• Areas around the front edge such as the front body and facings
• Reinforcement areas such as belts, waist areas, and pocket openings

Differences by Material and Type

The way thermal shrinkage appears varies depending on whether the interlining base fabric is woven, nonwoven, or knit, as well as the fiber type, density, type of resin, and amount applied. For shell fabrics as well, the response to heat differs depending on natural fibers, regenerated fibers, synthetic fibers, blends, and so on.

Even with the same material name, the degree and direction of shrinkage are not uniform depending on finishing, dyeing, structure, and grain direction. Because differences may appear between the warp and weft directions, it is basic practice to test fusible interlining in the same grain direction as the shell fabric.

Selection and Fusing/Sewing Precautions

Select interlining not only based on small thermal shrinkage, but by considering the shrinkage difference with the shell fabric, thickness, firmness, stretch, and drape performance as a whole. If a thick, firm interlining is used on a thin, soft shell fabric, the outline or stiffness of the interlining may show through the surface even if the shrinkage difference is small.

Carry out tests using the same shell fabric, interlining, cutting direction, and fusing conditions as in mass production, and check the dimensions, appearance, and whether there is any delamination immediately after fusing and after cooling. If temperature, time, or pressure is excessive or insufficient, problems such as shrinkage, strike-through, show-through, or interlining lift can occur.

In sewing, let the fused parts cool sufficiently before cutting or sewing them together, and align the grain. If sewing is done while distortion caused by thermal shrinkage remains, collar twisting, waviness at the front edge, and seam pulling are more likely to occur.

• Perform a fusing test with the shell fabric and interlining combined
• Set temperature, time, and pressure to match the fusing conditions
• After fusing, cool the material and check dimensions and appearance
• Select interlining that suits the thickness and firmness of the shell fabric

Differences from Similar Terms

Shrinkage rate is an indicator that shows how much dimensions changed before and after processing such as washing, drying, heat, or wet heat. Thermal shrinkage refers to shrinkage caused mainly by heat.

Shrink-proof finishing is a treatment to suppress shrinkage caused by washing or use. It is not a term that refers to thermal shrinkage itself. Also, interlining lift is a fusing defect in which the shell fabric and interlining do not adhere closely and appear to float, and thermal shrinkage difference can be one cause.

Frequently Asked Questions