Dimensional Stability and Paper Shrinkage
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 fibres in paper absorb humidity or moisture (e.g. 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 fibres 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.