BEATING ESPARTO 105
results, as the original length of the fibre is preserved and the long-continued
brushing out of the fibres gives the necessary fibrillation and subsequent wetness.
Esparto.—Esparto fibres are very fine and short; nevertheless they require
a certain amount of beating. This amount depends on the quality of the
grass and the treatment it has previously received. The fibres of Spanish grass
are tougher than those of African, and will stand more beating, thus giving a
stronger and harder paper. In order to eliminate shive, esparto fibres must
be well brushed or rubbed, with as little cutting as possible. This must not
be carried too far, as they are naturally slimy, and if the process is overdone
small knots will form in the chests and strainers and the web will stick to the
press rolls of the machine.
Sometimes a charge that has been overboiled or overbleached will defy the
efforts of the beaterman to make it into a good running paper, and then the
only remedy is to increase the proportion of wood pulp in the furnish. Esparto
is not suited for running over the machine without a proportion of chemical
wood fibres to form a base or framework for the paper.
As might be expected, esparto papers are very close and regular in com-
position and take a very clear water-mark. They take a very fine finish with
light calendering, and give a more bulky paper than wood pulp with the same
finish. For this reason they are most suitable for fine printing papers.
Esparto is very absorbent and requires a great deal of resin size to make a
hard-sized sheet. It produces an excellent tub-sized paper with a good hard
rattle and more strength than might be expected. The uniform size of its
fibres makes it very useful for the production of stamp and cheque papers, and
such papers as must have a very accurate register of the water-mark, and the
close even surface, which no other fibre can give, is very highly prized for fine
lithographic work. Some of the 'imitation art* papers made in this country
with a very large proportion of esparto are the finest papers in the world for
magazine printing.
The question of the proportion of sulphite wood and esparto used in the
furnish is often decided by the respective price of the two materials. It is in
the beating of esparto papers that many experiments have been carried out
with new and revolutionary designs in beating engines.
Some of'these have been quite successful, notably the Taylor and Tower
beaters, in which the stuff is circulated by a pump, up a pipe to the roll, which
stands at the top (see Hgs. 23 and 24, pp. 82 and 83). The main objects of these
beaters seem to be saving of floor space, quick circulation and a saving in power.
To get the best results from esparto it is essential that the preliminary
treatment should be regular, and beater tackle should be kept in a uniformly
correct condition.