Ironing of fabrics at the industrial level to remove wrinkles is known as:

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Accepted Answer

The correct option is 4:

The process of "ironing" fabrics at the industrial level to remove wrinkles, flatten the texture, and impart a smooth, lustrous finish is precisely known as **Calendering**. Calendering is a vital textile finishing process where the fabric is passed through a series of heavy, heated rollers under significant pressure, essentially acting as a giant, automated iron. This heavy pressing action mechanically flattens the yarns and the weave structure, permanently eliminating creases and wrinkles that formed during previous wet processing stages like dyeing and washing. Depending on the heat, pressure, and number of rollers used, calendering can impart various effects, such as a high gloss (Schreiner Calendering) or a simple, smooth, matte finish. It is a dry finishing operation performed towards the end of the manufacturing process to enhance the fabric's aesthetic appeal, handle, and market readiness. Therefore, the term is the specific, technical descriptor for the commercial equivalent of household ironing.

The incorrect option is 1:

**Mercerising** is a chemical finishing treatment applied exclusively to cellulosic fibers, most notably cotton. This process involves immersing the cotton fabric or yarn in a concentrated cold solution of sodium hydroxide (caustic soda) under tension. The primary goals of mercerisation are not to remove wrinkles but to dramatically alter the fiber's chemical and physical structure, leading to significant improvements in its quality. Specifically, mercerisation causes the cellulose fibers to swell and untwist, resulting in a permanent, beautiful increase in luster, a greater affinity for dyes (meaning deeper and brighter colors), and enhanced tensile strength. While a side effect might be temporary smoothing, its core function is chemical modification for quality improvement, not mechanical wrinkle removal.

The incorrect option is 2:

**Stiffening** refers to any finishing process used to make a fabric firmer, heavier, or more rigid in its structure and handle. This is achieved by applying a finishing agent, often referred to as 'sizing' or 'starch,' to the fabric to add body and resilience. Common stiffening agents include starches, resins, or certain synthetic polymers. The purpose of stiffening is to improve the fabric's drape, give it a crisp feel, or make it more suitable for certain end-uses like collar materials or mosquito nets. Far from being a process to remove wrinkles, stiffening is a property-enhancement finish, and if applied unevenly, it could even introduce stiffness-related creases or a harsh hand, which is the opposite effect of the smoothing action implied by industrial ironing.

The incorrect option is 3:

**Tentering** (or stentering) is a crucial mechanical finishing process related to dimensional stability and fabric geometry, not surface smoothing. It involves passing the fabric through a machine called a tenter frame, which uses clips or pins to hold the fabric along its selvedges (edges) and stretch it to a precise, uniform width. The main function of tentering is to correct the grain—ensuring that the warp and weft yarns are at right angles—and to dry the fabric to its final, specified dimensions after wet processing. By keeping the fabric under tension, it controls shrinkage and distortion, but its primary role is dimensional control and grain alignment, not the high-pressure smoothing and wrinkle elimination achieved through calendering.