THE WIRE 167
exactly what they want, and enormous strides have been made in the improve-
ment of wires and in the method of making the join during the last few years.
At this stage it is desirable to outline briefly some of these developments.
The first radical change in the construction of paper machine wires was the
introduction of long crimp or twill weave. This was done with the object
of increasing the life of the wire, and was first introduced for the manufacture
of newsprint. It remained as such for a considerable number of years. The
wire mark caused by this particular weave of wire was different from anything
previously known, and in a number of early cases was considered objectionable.
Various improvements in the weaving, however, have modified this mark in
the under side of the paper, and in nearly every case newsprint is manufactured
over twill wires, certainly on the wide machines 19 feet and over in width.
Various developments and improvements of the twill weave permitted its
application for the manufacture of finer papers, and various weaves are now
on the market known under the different titles applied to them by their various
makers, such as Superfine Quality, Flat Warp, etc., the object of these fine
weaves being to present as many places of support as possible to the under side
of the sheet during formation, and so prevent any prominent knuckle imprinting
itself into the web. The question of wire mark is no longer the source of worry
that it used to be to tie fine paper-maker, and in some cases in paper
made on these new weaves it has been almost impossible for anybody but the
expert to say which was the top side and which the under side. The paper-
maker, therefore, who wishes to avoid wire mark must co-operate with the
wire-makers to provide him with the most suitable formation of weave for
his purpose.
Another very valuable attribute of these wires is the improved shape of
hole. In the ordinary plain weave the hole is of a very oblong shape, whereas
with the newer weave it is very much squarer, with a consequent reduction
in the loss of fine fibres. This can be readily seen by a comparison between
Figs. 53 and 54, both of which are 72-mesh photographed at the same magnifica-
tion, but No. i is the old plain weave and No, 2 a Superfine equal to 72. It
is particularly interesting to note that the use of 90, 80 and practically all 76-
mesh wires of plain weave has been discontinued in favour of these new weaves,
with none of which it is necessary to go finer than 72.
It is not unusual, however, for milk making a wide range of papers, both of
quality and substance, to keep to one mesh and to vary the furnish and beating
to prevent 'wire mark*, or to enable the paper to run on a fine mesh wke.
When there is more than one machine, it is more economical and efficient
to use wires with different meshes and run on each the quality that is best
suited to it