Warp yarn

The warp (German Kettfaden) is the set of longitudinal yarns of a woven fabric. Before weaving, they are wound onto the warp beam in parallel and held under tension on the loom. Heddles raise or lower them to create the shed through which the weft is inserted.

Because warp yarns endure continuous tension and abrasion during weaving, they must be strong and smooth. They are frequently sized (coated with starch, PVA or wax) for strength and later desized. Warp yarns are usually plied or have higher twist than weft.

• Warp density = warp ends per cm
• Warp direction defines the grain line for cutting
• In ripstop, denim, twill and poplin the warp yarn largely determines tensile strength and hand