Preparatory Processes: Winding, Warping, Sizing and Drafting
Preparatory Processes: Winding, Warping, Sizing and Drafting
This domain tests the order and purpose of the pre-loom operations and the small calculations that follow from them.
Purposes
- Winding: transferring yarn to a suitable package - weft on pirns or bobbins for the shuttle, warp on cones or cheeses - while removing slubs and weak places and setting uniform tension.
- Warping: assembling the required number of ends to the correct length and width. Direct (beam) warping suits long runs, sectional warping suits patterned stripes, mill warping suits short lots.
- Sizing: coating warp yarn with size (starch, CMC or PVA) to raise abrasion resistance and cut breakage; measured as % size add-on.
- Drafting/drawing-in: threading each end through its correct heald eye. Denting: passing ends through the reed, often 2 ends per dent. Gaiting/tying-in: attaching the warp to the cloth beam.
Worked example
A warp is 42 in wide at 64 EPI with 2 ends per dent. Ends = 42 × 64 = 2688. Dents = 2688 ÷ 2 = 1344. Dents per inch = 1344 ÷ 42 = 32, so a 32-dent reed with 2 ends per dent gives 64 EPI. If the warp weighs 20 kg at 8% add-on, size = 20 × 0.08 = 1.6 kg.
Marks-losing traps
- Confusing ends per dent with ends per inch.
- Applying size add-on to the sized weight instead of the unsized warp weight.
- Heavy starch sizing on muga or eri silk - it dulls natural lustre, so these get only light sizing.
- Skipping lease rods, which causes crossed ends and warp breakage.