Paper Mould and Deckle

Cut four hardwood rails 30 x 20 mm to make a frame of your target sheet size — A5 is a sensible start. The frame must be stiff; it takes real tension from the screen.

Join the corners with half-laps or mortise and tenon and check both diagonals are equal. An out-of-square mould makes out-of-square paper, permanently.

Fit two or three ribs across the frame, their top edges level with the rails. Ribs stop the screen sagging in the middle — the traditional mould is reinforced exactly this way.

Round or bevel the top of each rib so it touches the screen along a narrow line. A flat rib pressed against the screen prints a visible pale stripe into every sheet.

Give the whole frame several coats of varnish or oil. It will spend its life wet, and unsealed wood swells, moves out of square and eventually rots.

Stretch fine mesh over the frame, pulling from opposite sides alternately, and staple it down all round. Tightness decides sheet evenness — a slack screen forms a thick patch wherever it dips.

Trim the surplus mesh and cover the fixings with a thin batten or tape. Exposed staples snag the wet sheet as you lift it off.

Make a second open frame the same outside size as the mould, with no screen. This is the deckle, and it is entirely separate — not hinged, not fixed.

Plane the deckle's underside dead flat and test it on the mould. Any gap lets pulp escape under the frame, and that corner of the sheet comes out thin.

Hold the deckle on the mould, dip vertically into the pulp vat, level out and lift straight up. Shake gently fore-and-aft and side-to-side while the water drains — that shake is what interlocks the fibres in two directions and gives the sheet its strength.

Once the water has drained, lift the deckle straight off, then press the mould face-down onto a damp felt and roll it away to release the sheet. That transfer is called couching.

Hold the dry sheet to the light. Thick patches mean a slack screen; pale stripes mean flat rib tops; a thin edge means the deckle was not seating. Every fault in the paper points at a specific fault in the mould.

Two frames, two jobs. In the Western tradition the toolset is a mould carrying a permanently fixed stiff mesh, plus an entirely separate open frame — the deckle — that fits over it to contain the sheet being formed. The mould is built as a rectangular wooden frame reinforced with ribs, over which a coarse backing wire is mounted and a finer screen stretched tightly and secured all round.

Laid and wove. Two screen types. A laid screen is made of closely spaced parallel wires and prints faint lines into the sheet — hold old paper to the light and you can count them. A wove screen is woven in a plain square weave, typically around 40 wires per inch each way, and gives an even surface with no lines. Wove paper is the later invention, and the difference is visible enough that it helps date documents.

The deckle edge. A small amount of pulp always creeps under the deckle frame, thinning toward the edge. The resulting soft feathered border is the deckle edge — the physical signature of hand papermaking, and so desirable that machine papers are sometimes made to imitate it artificially.

Why the shake matters. Fibres in the vat drift with the flow. Shaking the mould in two directions as the water drains lays fibres across each other rather than all one way, and that random interlocking is what makes paper strong in both directions. A sheet formed without the shake tears easily along one axis. It is a two-second movement carrying most of the mechanical properties of the product.

Bronze, and then synthetics. Traditional screens are fine bronze wire, which does not corrode at neutral pH. Synthetic mesh later brought large savings — it lasts longer, is easier to keep clean, and its tighter weave retains more fibre in the sheet and loses less back to the vat. A rare case where the modern substitute is better on almost every axis, which is why most working papermakers now use it.