MULTIPLE WIRE MACHINES 253
This roll has the devices and lettering, etc., fixed to its woven-wire cover,
and as it revolves it picks up a layer of stuff, thick where the cover is plain cloth,
and thin where the device wires are placed.
The wet film of stuff is couched off at the top and taken on a felt to the
presses in exactly the same way as the stuff is couched off the dram of a board
machine.
If the paper is to be made in single sheets, strips of wire are placed round
and across the roll to fix the dimensions of the sheet. No stuff, or very little
stuff, adheres to this wire, so that when the wet sheets have been pressed they
come apart, or are easily pulled apart by hand, leaving a 'deckle' edge.
The machines are so arranged, and fitted with four or five or more drying
cylinders, that the paper may either be dried at once by steam, or may be
removed from the felt by hand as wet waterleaf and dried by air in a loft.
The Richardson-Key expanding cylinder 'mould' is sometimes used on
these machines, owing to the ease with which a new wire cloth cover may be
fitted when changing from one water-mark or size to another. This patent
'mould' enables a great saving to be made in the stock of 'moulds* or drums,
which would otherwise have to be carried.
Two AND MULTIPLE WERE MACHINES
In recent years increasing use is being made of Fourdrinier machines with
more than one wire. The object of this is twofold. In the first pkce it enables
a paper to be produced with two top sides on which to print. This is achieved
by running together the under or wire sides of two thin papers, leaving the
two top sides outermost. It is thus possible to produce a printing paper with
exactly the same surface on each side of the sheet. The method is also applied
to make paper of very great strength, and two or more wires may be used
for this, giving a two- or three-ply sheet Some mills have been doing this
for a long time, but the practice has not been general. More frequently a
Fourdrinier wire has been used in conjunction with a vat such as that used on
a mould machine, but now that the difficulties of combining the two sheets
at the press have been overcome, the use of two complete Fourdriniei: wire
parts to form the sheets is quite common practice, llie sheets are brought
together at the press, where they become homogeneous and pass on through
the second and third press and across the dryer as one solid sheet.
It is not, of course, possible k this case to make satisfactory laid or water-
marked sheets. . •