Papers
which are treated in this way are known as "animal," or "tub-sized."
We have duly described machine-dried papers, but these higher grades of
writing-papers are dried by what is known as the loft, or pole-dried
process. Such paper is permitted to dry very slowly in a loft specially
constructed for the purpose, where it is hung on poles several days,
during which time the loft is kept at a temperature of about 100°
Fahrenheit.
Another detail of considerable importance is that of the "finish" or
surface of the paper. When paper with a particularly high or glossy
surface is desired, it is subjected to a separate process, after leaving
the paper machine, known as supercalendering.
"Supercalendering" is effected by passing the web through a stack of
rolls which are similar to the machine calenders already described.
These rolls are composed of metal cylinders, alternating with rolls made
of solidified paper or cotton, turned exactly true, the top and bottom
rolls being of metal and heavier than the others; a stack of
supercalenders is necessarily composed of an odd number of rolls, as
seven, nine, or eleven.
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