Grain of paper refers to the direction of
paper fiber, which is parallel to the moving direction of paper machine, also
known as machine direction (MD), and cross direction (CD) which is
perpendicular to the running direction of paper machine. Many properties of
paper have obvious directionality. The tensile force and kneading resistance in
the longitudinal direction (MD) are relatively strong, while the tearing degree
is relatively weak and easy to tear off. Because the grain is longitudinal, it
is difficult to tear off in the transverse direction. After the web is cut into
flat sheet, its grain has two names: 1. Long grain, also known as straight
grain, referred to as LG, its grain goes along the long side, that is, the
paper fiber is parallel to the long side. 2. Short grain (short grain), also
known as transverse grain, referred to as SG, its grain along the short side,
that is, the paper fiber and short side parallel. The natural pattern of paper
is an absolute concept, which is different from the pattern of paper embossing.
Long or short lines of paper is a relative concept, relative to the size of the
paper. If a positive paper is long grain, after the split is short grain.
Therefore, in the book
printing process, if you do not pay attention to the paper texture, then
the printing effect can be very different. Especially in case or bag printing.
In order to save costs, some printing factories cut the paper at will when they
open the paper, regardless of the direction of the paper grain. As a result,
some packaging boxes produced are relatively strong, but some packaging boxes
are relatively weak, some packaging boxes are always easy to break, and some
packaging boxes will not have problems for a long time. Especially for handbag
printing, a large part of the parting bags are three open, and the horizontal
one-third of the paper grain is far away from the vertical one. If paper itself
is not good paper, the difference is even greater. Such products are absolutely
not allowed in high-end printed matter. Some book
printing salesmen have been working for several years, but they
still don't understand this truth. They are all the same paper. Why do they
produce some solid and some weak results? Some edges are always broken, but
some are intact. Some edges are rough and some are smooth and clean.
