This information is reprinted from the Cranberry Corner column of Hand Papermaking Newsletter #52 (October, 2000).
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Western Moulds / Watermarks
This time we will describe the Western style mould and deckle, and watermarks.
THE MOULD. The mould consists of a rectangular wooden frame reinforced with wooden ribs, over which a coarse mesh backing wire is mounted, and then a finer mesh screen is tightly stretched over it and secured all around.
Professionally made moulds are made with strong, lightweight mahogany wood fastened with brass corners. The screens used for these moulds are made from fine bronze wire which does not corrode under normal neutral pH conditions.
There are two types of wire screens used, “wove” and “laid.”
A “wove” screen is woven using a plain or square weave pattern, typically a warp of 40 wires to the inch by a weft of 40 wires to the inch. Due to the fineness of the wires and of the mesh, and the very light drainage forces that occur while forming handmade paper (compared to machine made), there is usually no evidence of a “wire mark” in the paper from a wove screen.
A wire mark occurs when the pulp fibres are forced in and around the raised knuckles of the wire mesh during the forming process as the water drains away, which then leaves an impression of the wire mesh in the paper.
Warp refers to the wires oriented in the direction of travel of the screen through the weaving loom, and weft refers to the wires that are oriented across the loom.
Amateur moulds can be made by using a less expensive wood for the frame on which is tautly strung a polyester monofilament screen, supported by a coarser weave, stiff, stainless steel or brass backing screen.
A “laid” screen is made on a special loom which lays out pairs of warp wires twisted into “vertical” cables which may be spaced apart typically one to one and one-half inches. The horizontal weft or laid wires are strung across these cables, evenly spaced apart at about 1/16” intervals, and secured by the twist of the warp cables as the laid wires pass through them.
Due to the relatively large diameter of the cables and the wider spacing of the laid wires, the pattern of this screen is visible as a wire mark in the paper. This laid pattern is particularly evident in lighter weight papers such as are used for stationery.
THE DECKLE. The deckle is a rectangular wooden frame each side of which is cut way at the back with grooves like a picture frame, under which the mould fits. The corners may be tongue-in-groove and brass reinforced for strength. The frame members are typically 1-1/4” wide.
The deckle fits snugly over the mould thus providing a raised edge around the mould about 3/8” above the screen level within which the pulp suspension is dammed while the water is drained away during the forming stage.
In order to speed up production, it is possible to make one deckle with two or more frames incorporated in it. This fits over a large size mould. With such a multiple deckle it is possible to make two or more sheets of paper at a time with each dip of the mould and deckle into the vat.
WATERMARKS. A watermark is similar in nature to the wire mark mentioned above, i.e., it is an impression in the paper. Watermarks are created for identification or decoration. Thus the identity of a papermill, paper grade, paper maker, client, and/or date of manufacture, etc., may appear in the sheet of paper. It is also possible to create artistic images such as a person’s profile.
A simple watermark is created by securely sewing an outline image made from relatively coarse brass wire onto the top of the wire screen on the wove or laid mould, using fine brass wire. When mounting the watermark on the mould it is placed with the image reversed (mirror image), and near the lower right hand corner of the screen. Thus the positive image of the watermark is seen in the lower left hand corner of the sheet of paper when viewing it from bottom side (or wire side) using transmitted light.
As the sheet forms, the fibres of the pulp slurry flow around the wires of the watermark and are displaced by them. This results in the paper being thinner where the watermark wires are located. The paper is thus less opaque (more translucent) in the image areas and transmitted light shines through the paper more easily showing the outline of the watermark. As with the laid wire mark, watermarks are more visible in lightweight paper than in heavy weight paper.