In which type of clothes gum starch is used?

Starching is a laundry-finishing process in which a thin film of a starch- or gum-based polymer is deposited on fabric fibres to add stiffness, body and a smooth finish. The starching agent must match the fibre's chemical nature: a coarse plant starch (rice or wheat flour, i.e. kanji) suits strong cellulose fibres, while delicate protein fibres need a finer, softer sizing agent such as gum (gond) so the fibres are not roughened or damaged.

Applying this to the given options: among woollen, cotton, silken and nylon clothes, silk is the delicate natural protein fibre. To stiffen silk garments (for example sarees and formal wear) without damaging their fine texture, a refined gum starch (gond ka kalaf) is used instead of an ordinary plant starch. This is exactly the agent named in the question, so gum starch is used on silken clothes.

• Woollen clothes: wool is a delicate animal-protein fibre that is generally washed gently or dry-cleaned; it is not given a starching treatment, since starch would stiffen and damage its natural elasticity and insulating loft.

• Cotton clothes: cotton is a cellulose fibre that does take a stiffening agent, but the agent used on cotton is an ordinary starch (a rice- or wheat-flour paste), not a gum-based one.

• Silken clothes: silk is a delicate protein fibre, so a refined gum-based starch is used on it instead of a coarse plant starch, adding stiffness without roughening the fine fibres.

• Nylon clothes: nylon is a synthetic polymer fibre that is already smooth and wrinkle-resistant by manufacture; it does not absorb or require a natural starch/gum finish the way natural fibres do.

So, among the given fabrics, gum starch is specifically used on silken clothes.