A hand-made sheet of paper does not begin as a sheet. It begins as a vat of water with a small amount of fibre drifting in it, so little that the liquid looks almost clear. The papermaker takes a rectangular frame strung with fine bamboo filaments — a screen — dips it flat into the vat, and lifts. Water runs away through the gaps; fibre stays behind as a wet, barely coherent film. Everything that follows is an attempt to keep that film intact while the water leaves it.
The screen is the mould
The gaps between the screen's bamboo filaments are far narrower than the length of a single fibre. A fibre carried across a gap bridges it, catches on its neighbours, and is held, while the water passes through freely. The screen is therefore not a strainer in the kitchen sense: it is a mould whose entire surface is a filter, defining both the size of the sheet and its thickness in one movement.
Thickness is set by two things the maker controls without instruments: how much pulp is in the vat, and how fast the screen is brought up. Lift too quickly through a thin suspension and the layer has holes; linger in a rich one and the sheet comes up opaque and heavy, with fibres that never quite settle. A slight rocking motion as the screen rises is what spreads them into an even mat — and the direction of that rocking decides how the fibres lie.
A sheet pulled with one steady motion has most of its fibres pointing the same way, so it tears more readily along one axis and folds cleanly along the other. Rock the screen in two directions and the mat becomes more even, weaker in any single direction but more predictable overall. The screen leaves its own signature too: fine parallel laid lines, visible when the finished sheet is held up to a window. Those lines are not a defect. They are a record of the tool.
Where the strength actually comes from
A freshly lifted sheet has almost no strength at all. It is mostly water, and what holds it together for those few seconds is the water itself. Turning the screen over and laying the wet film onto a board without tearing or creasing it is the most delicate moment in the whole craft; peel the screen away too fast and the film comes with it.
The stack of wet sheets is then pressed to drive out more water, and the sheets are brushed onto a smooth wall or board to dry. As the last of the water leaves, the fibres are drawn close enough for hydrogen bonds to form between their surfaces. No glue is added at this stage. The sheet becomes paper during drying, not during dipping — the vat only arranges the fibres, and the drying joins them.
That also explains an old inconvenience: wet the finished sheet again and it softens, because water competes for those same bonds. Coating paper with a drying oil closes the pores and keeps water out, which is exactly what an oil-paper umbrella does. Sizing for writing, and mineral fillers for a whiter surface, came later; they change how ink sits on the sheet, not what holds the sheet together.
The material of the screen matters as much as its weave. Bamboo can be split into filaments that are long, straight and springy enough to stay taut when wet, and it does not swell much between one dip and the next. How thin a bamboo strip can be split is the same question the screen maker is answering, only with the tolerance taken to a much finer scale: here the strip must be fine enough to leave only a faint line, and stiff enough not to sag under a film of water.
What the finished sheet remembers
Drying against a smooth surface leaves one side polished and the other slightly fibrous, so a hand-made sheet has two different faces. It shrinks as it dries, and the edge that was held longest shows a thin irregular deckle. For a paper lantern or an umbrella canopy, the maker wants a sheet that is thin, even and able to take a coating without tearing — all three decided back at the vat, before any cutting or folding begins.
There is a quick way to see the difference. Tear a hand-made sheet slowly and watch the edge: fibres pull out in a fibrous fringe and the direction of the tear wanders. Tear a machine-made sheet and the line runs straighter, because the fibres were laid down by a moving wire in a dominant direction. Same material, same chemistry, different answer to the question of how to get fibre out of water.
The whole craft is therefore a piece of transport engineering. Water carries the fibres, separates them, and gives them a chance to lie down flat; the screen takes the water back; drying turns the arrangement into a solid. No press forms the sheet and no adhesive is required. The sheet is, quite literally, lifted out of the vat.