For the filter, I bought the thickest unbleached muslin available at the local fabric store, and cut it according to a sewing pattern we prepared ourselves. The reason we decided on a shallow half circle instead of a cone was because the water was to be poured in a thin stream. For the filter’s circular rim, I bent a stiff 3mm wire around a whiskey bottle. I crafted the handle by opening a hole into a replacement handle for a file. A brand new filter is first boiled in hot water and mixed with some coffee to soak in before use.
(Katsuji Daibo, “A Daibo Coffee Manual,” pp. 9-10)
He found the ideal material for his nel drip coffee: the thickest unbleached muslin (with a single brushed side) for straining consommé soup. This was achieved through a process of trial and error.