AIR-DRYING

297

With pure rag paper, where the resin does not exceed i per cent, the quan-
tity of resin added to the feculose solution should be doubled.

j

The sizing may be carried out in the ordinary size-tub of a tub-sizing machine
and the paper then dried by hot air. As an alternative, however, a bath of
feculose of about 10 per cent strength may be placed after the presses, and
immediately before the steam-drying cylinders of the machine. In order
to give full ink resistance, resin size is added to the feculose in the bath and
precipitated in the usual way by alum. The heat of the drying cylinders does
not affect the feculose size adversely, as is the case with gelatine.

Paper sized in this way should not be called 'tub-sized5, as this term has
long been applied to high-grade papers sized with gelatine, and it is likely to
be misleading.

[Messrs. Masscn, Scott and Co.

FIG. 128.—SECTION OF TUB-SIZING AND AIR-DRYING MACHINE, SHOWING HoT-Ant BLOWER ON TOP SECTION
The dried web is brought back to the bottom floor to be calendered

Air-Drying.—To carry out this operation the paper is led over a series of
sparred drums about 3 feet in diameter by means of cotton tapes. The drums
are composed of iron ends and spindle and have wooden spars* Some of them
are also fitted with metal fans revolving in the opposite direction, in order
to agitate the air and keep it in motion, and these fans also assist in keeping
the paper flat and preventing it from running into creases. They are generally
arranged in tiers.
Attempts have been made to dry a tub-sized paper in an enclosed dryer
where hot air can be circulated, and thus dry the paper quickly and in a much
smaller space than is required with the ordinary sparred drums in a heated
room. So far as we are aware, however, up to the present this method has
not been found very successful.
A typical air-dryer is illustrated in section in Fig. 128. If the paper has to