Weaving a Water Filter Cloth to a Stated Pore Size: The Ends per Inch That Deliver It, and What the Flow Costs

Woven cloth is the oldest filter medium in the world and still the one a village workshop can make for itself, but a filter is specified by its pore size while a loom is set by thread counts, and the translation between the two is rarely written down. This paper writes it down. For a plain weave in a stated yarn, it derives pore width from ends per inch, computes the open area and a comparative flow index for the resulting cloths, estimates capture of a stated particle size, and selects the coarsest sett that meets a stated pore target, because the coarsest adequate cloth is the one that flows fastest and clogs slowest. In the computed results, the chosen epi is 92; the chosen pore um is 56.1; the chosen capture pct is 74.8; the chosen flow index is 0.3; the coarse epi is 45. Set the reed from the pore target, not from the cloth's appearance: ends per inch equals 25.4 divided by the sum of the target pore and the yarn diameter, in millimetres. 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.