Cutting the Reed Width Right First Time: A Shrinkage Rule for Cotton, Linen, Wool and Silk Warps

Cloth leaves the loom narrower than the warp was sleyed, because the weft's crimp relaxes, the warp's tension releases, and the fabric settles into the dimensions it actually wants. Every weaver learns to allow for the shrinkage; many learn it as a single percentage carried from cloth to cloth. This paper shows what that single percentage costs. Shrinkage is computed from a stated model depending on fibre and weft density, the reed width that a 90 cm finished cloth actually requires is derived for cotton, linen, wool, and silk at three densities, and the finished width produced by the common flat five percent allowance is calculated for comparison. In the computed results, the cotton14 shrinkage pct is 9.1; the cotton14 reed cm is 100.2; the cotton14 naive error cm is -3.9; the wool14 shrinkage pct is 11.1; the wool14 reed cm is 102.4. Compute the reed width from the fibre and the planned weft density, every time, using reed width equals finished width divided by one minus the shrinkage fraction, and add the selvedge allowance separately. The study is simulated, not measured; all inputs are stated assumptions, printed in the accompanying computation, which readers may replace with their own values and re-run.