Fabric Relaxation Dwell before Cutting

Two exponentials are the smallest model that reproduces what cutting rooms actually observe, and real cloth has a spectrum rather than two terms - so the fit will be good in the middle of its range and poorer at both ends, over-predicting relaxation in the first few minutes and under-predicting what is still creeping out after several days. Fit the constants by measuring a marked length on a roll at intervals rather than taking them from anywhere else, because they differ enormously between a stable woven and a high-elastane knit, and it is the knit that makes this calculation worth doing. Strain here is treated as fully recoverable, which it is not: part of what was put into the cloth at finishing is set rather than stored and never comes back, so the residual figure is an upper bound on the movement to expect. That is the safe direction. The panel error assumes the strain is uniform along the panel and in one direction; a lay spread with varying tension relaxes differently down its length, which produces panels that differ from each other rather than panels that are all the same wrong size, and that is much harder to correct for in the marker. Nothing here covers the relaxation that laundering releases, which is a fabric shrinkage question rather than a dwell question.