THE WIRE 169
web is formed on the wire, and that sheets of different formation and appearance
may be made on the same wire by altering slightly the lateral movement of the
wire frame and/or the amount of water in the stock, but the formation of the
sheet—even of a very strong sheet--is accomplished in a very short distance
along the wire. After the stuff has settled down—say half-way along the wire—
tio change in the position of alignment of the fibres appears to take place, and
the wire is simply carrying the web along to the first suction box. There is
something else happening, however— i.e., the removal of water by each of the
tube rolls. This water can be just as well removed by an extra suction box or
two, so that the difficulty of a short wire can be easily overcome.
On these machines where a Voith slice is used it is no longer necessary to
take up 2 or 3 feet of wire by covering it with an apron or pond of stuff behind
the slices, so that this gives more actual paper-making length on the wire.
It must be remembered, however, that there is a tendency now to prevent
water being taken out by the first few table rolls, in order that the effect of the
shake may be brought to bear on the fibres while they are still floating in water
which is not passing away through the wire. There is also a tendency for
table rolls to be substituted by flat boards or smooth surfaces of stationary
metal for the first 12 inches or more of the wire after it leaves the breast roll.
There are a good many fairly old machines ninning at the present time
on which very strong rag papers are made, where great difficulty is experienced
in getting the water out before the dandy and couch roll, resulting in 'crush-
ing* and spoiling of the sheet. Sometimes it is quite impossible to make the
required sheet for the following reasons:
1. The stuff is too wet and the wire too short for water extraction, if suffi-
cient water is put on to 'make' the sheet.
2. If water is put off at the stuff box the stuff is too inert and greasy to
shake together properly when it reaches the wire. It will also be found that
if water is put off the stuff cannot be got through the strainer, especially if it
is long as well as wet.
3. If sufficient water is put on to get the stuff through the strainer and to
make the sheet on the wire, then there is too much water at the dandy and
couch rolls. Heating the stuff will help matters, but in order to get over the
difficulty permanently there are two alternatives only. First, to put in one or
two more suction boxes, with separate vacuum pumps, or increase the length
of the wire and the number of tube rolls.
Really wet, thick stuff, for strong ledgers, parts very slowly with its water,
and gradual but not too fierce suction is necessary if the work is to be properly
done.
' The Seam.—This is die place where the two ends of the wire dodb have