The importance of climate-controlled storage is well known for wine. Now we look at the detrimental effects of extreme environmental shifts on organic materials, like paper, books, photographs, leather, fabric, and wood. This pertains to musical instruments, too, as they are comprised of these materials.
It is always a good idea to use climate-controlled storage for important documents, keepsakes and pictures. As with wine, chemical reactions exponentially accelerate at high temperatures. Paper contains natural and added chemicals, which break down over time causing pages to yellow, and pictures to fade.
Without proper climate-controlled storage temperature fluctuations occur and are closely linked to humidity levels. Warm, moist environments are attractive to insects, molds and mildews, which feast on paper and other organic materials and also cause physical breakdowns, like curling, swelling and shrinkage. Most of this is due to water being absorbed from the air. The thinner the material (i.e. paper) the quicker the damage occurs. Warping, peeling and cracking results when varying thicknesses, densities or grains of materials expand and contract at different rates. Glued items may fall apart, as glue becomes porous and wet, losing its ability to bind materials that are working against each other. Fabric threads contract in length and expand in width, becoming weak, susceptible to rotting, breakage and fading. Leather also absorbs water, resulting in cracking if the humidity drops rapidly, color fading, stretching or buckling if on furniture.
Paintings become ruined as their different layers (paint, canvas, frame) break down at different rates and in different ways (swelling, contracting, warping). Sadly, damage to pictures, paintings and other organic materials often cannot be undone, so the best way to ensure a long, beautiful life is proper storage in the first place. Control temperature and humidity levels at home as much as possible, and keep books stacked closely together. If you must store items, even for a little while, consider a climate-, humidity-, dust- and pollution-controlled environment.