Early Japanese papermakers astutely noticed that pulp containing Gampi fibres had a slower drainage rate allowing the papermakers to repeatedly move the pulp mixture back and forth over the mould’s surface, which in turn resulted in a stronger paper (with more evenly intertwined fibres). It was subsequently discovered that Gampi releases a viscous liquid that actually changes the viscosity of the water, further slowing the drainage rate. For some time, Gampi fibres were added to other fibres to achieve this effect but since Gampi is not easily cultivatable, it was difficult to obtain significant quantities. This key viscous material, or “neri”, was then extracted from other more readily available plants leading to the development of the “Nagashizuki” style of paper-making which yields the strong, thin and semi-translucent papers that has become synonymous with washi.

The Nagashizuki method often uses a wooden mould and deckle unit with a removable flexible bamboo screen. Long-fibered pulp is mixed with natural “Neri” to change the viscosity of the water and suspend the fibres during sheet formation process - resulting in a similarily slow drainage process.

The Nagashizuki method has three basic actions: The first,“Kakengashi” requires a small scoop of the pulp mixture; just enough to only cover the screen surface. The pulp quickly flows across the screens surface with excess pulp tipped out over the far edge of the mould. This quick motion aligns the fibers perpendicular to the splints of the bamboo screen surface and forms the “face” of the paper. This motion makes it easier to eventually remove the newly formed sheet of paper from the screen. 2nd is “Choshi”, when a larger scoop of pulp flows back and forth evenly coating the entire screen. It’s important that some pulp mixture remain in the mould to help counter the pressure of the pulp mixture from the backside of the screen when the next scoop is taken. This action is repeated several times until the desired paper thickness is achieved. The thickness is built up layer-by-layer enabling the long fibres to become well entwined. The 3rd action,“Sutemizu” is a bit similar to the first as the pulp mixture is quickly flowed over the entire surface with the excess tossed off the far end of the mould. The quick motion aligns the fibers in a single direction and forms the back of the paper. The manufacture of strong and semi-translucent sheets of paper is possible using the Nagashizuki method but this method also can lend itself to a variety of paper thicknesses and characteristics.