Shirt interlining is an extra layer of fabric added to the interior of garments to add thickness

Shirt interlining is an extra layer of fabric added to the interior of garments to add thickness, aid seating flatness, and prevent creasing for a professional finish. Interlining can also help stiffen areas of clothing such as collars and plackets for better fits; an essential addition for professional shirtmakers! Various weights and styles of interlining are available and it is either sewn on using heat and pressure or adhered with glue or fused using both heat and steam fusion techniques.

An interlining for shirts typically comprises lightweight woven fabrics such as cotton, polyester or silk and is often treated with starch or other finishing agents like water-soluble starch to improve its properties such as shrinkage resistance and crease recovery. Flame retardant agents may also be added.

Traditional interlinings were usually constructed from wool or cotton; however, recently synthetic and other high-performance fabrics have become an increasingly popular choice. Elasticity is a critical factor when assessing an interlining's quality; too rigid interlining could cause fabric tears that compromise its shape and appearance resulting in poor shape retention for final product shape and appearance.

Additionally, the type and cut of interlining can drastically alter its purpose and performance. For instance, shirt collar interlinings can be classified into hard and soft versions to meet different design needs; hard collar interlining will keep its shape without stretching while soft ones allow some movement between designs.

Most shirtmakers prefer using bonded interlining as it can be easily fused onto fabric using heat and steam, making its seams less visible while providing greater strength than traditional stitching methods. Furthermore, applying this lining once both front and back panels have been sewn together makes for faster construction time.

Rainbow uses floating lining collars, which may be more comfortable against the neck than their fused counterparts. Unfortunately, however, making such collars requires more skill as you must form and stitch around its shape - and wrinkles may develop as a result of stitching around it. Furthermore, controlling its size becomes harder; gapping may occur between it and its band or cuff which would look odd when worn with a tie.