Why do irons work so much better when hot?
Cloth fibres are bound together by chemical bonds, the polymer strands becoming fixed in unnatural shapes (wrinkles) as the fabric bends.
These bonds are weakened by heat, so when a hot iron is applied, the cross-linking between the fibres is loosened, allowing the weight of the iron to force them into a new, flatter shape.
As soon as the heat is removed, the polymers re-bind into their new position and, voila, a freshly pressed shirt, skirt or pillowcase. Apply weight without heat and the job is much harder unless water is added too – hence the wrinkle-busting power of the steam iron.
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