Dimensional stability is a term used by papermakers and paper converters to
describe the property of paper to change its dimensions as moisture or humidity
levels change. These changes in humidity may be associated with wetting or
drying processes. Some aspects of dimensional stability, such as paper curl, are
largely under the control of the papermaker, while others such as shrinkage or
print register are influenced to a large extent by both the papermaking process
and the selection and treatment of fibre. Many paper grades are sensitive to
issues of dimensional stability, for instance LWC and ULWC, offset printing
grades, wallpapers and décor grades.
When fibers in paper absorb humidity or moisture (eg: during offset printing),
they swell more across their width than they do along their length. This
property is known as hygroexpansivity. In most cases swelling in the finished
paper will be greater in the paper's CD, because more fibers are oriented in the
MD and because the initial paper shrinkage in the MD was limited during drying.
This presentation is a summary of some of the more relevant research and
knowledge relevant to this important subject. In summary, fine, thin walled
fibres, lightly refined and free from excessive fines, provide the best
combination of tensile strength, reinforcement and dimensional stability.
