Heat setting is a heat treatment process that imparts shape retention, crease resistance, resilience and elasticity to fibers. It involves four phases: heating, penetration, transition and stretch, and cooling. Heat setting can be carried out at different stages - in grey condition, after scouring, or after dyeing. Different methods are used for heat setting including contact, steam, hydro, tenter frame, and selective infrared methods. Heat setting results in structural and chemical modifications of fibers that change properties like strength, stretchability, softness, dyeability and sometimes color.