Art Materials - Paper
Most of the objects we frame are works on paper. In framing works on paper we take into account the many differences in the nature of various papers.
Japanese papers are often light; some are like gossamer, with a modest sizing of vegetable gelatin to reduce water absorption, so they are very pliant.
Western papers are usually stouter and more heavily sized, so static charge is rarely a concern. But they are heavier and may require stronger hinges than Japanese papers.
European papers were generally made from linen rags until the late 18th century, when cotton gradually displaced linen for cloth. Even now excellent papers are made from cotton, though not from rags but from virgin fibers. These papers are still known as “100% cotton rag” paper. The best matboards are made from this material as well.
Most modern and contemporary works on paper utilize machine-made paper which has a decided grain direction. The sheets expand and contract with changes in humidity far more across the grain than parallel to the grain.
Late 18th—mid 20th century paper
Early hand-made papers were usually long-lived, and most fine art papers made in the past few decades, whether hand-made or machine made, are of high quality. But papers made from the late eighteenth c. through the mid 20th c. often carried seeds of their own destruction. Paper was often made from wood pulp whose impurities were not removed. To make them white, sheets were bleached and imperfectly rinsed. European papers were traditionally sized with animal gelatin to reduce their absorption of water, but by 1850 paper was sized with alum-rosin sizing which in fairly short order caused its destruction. The net effect of these changes in paper making technology was disastrous. The life of a sheet of paper, which could be thousands of years, was often reduced to decades.
Of course, artworks may be made with plastics and other materials whose properties differ from paper in their reactions to light and to changes in temperature and humidity. Their properties must be taken into account in framing them.