Perhaps the greatest environmental damage to furniture comes from wide swings in relative humidity (RH). Wood absorbs and desorbs water as relative humidity rises and falls, and in doing so it swells and shrinks. Making matters worse, it expands and contracts unequally along different grain directions. This characteristic remains as long as wood exists, whether it is new from the lumberyard or thousands of years old from an ancient tomb.

As humidity changes, the components of wooden objects are continually pushing and pulling against each other. This pressure often results in parts of furniture no longer fitting together closely or becoming distorted or breaking from their own internal stresses.

Wood is not the only furniture component to suffer from humidity swings. As they age and deteriorate, coatings become more inflexible. Since the wood continues to move with humidity changes, and the coating becomes increasingly brittle with time, humidity fluctuations eventually cause the coatings to begin fracturing or separating from the substrate. This problem becomes particularly severe when coatings are likely to be less flexible from the start, such as painted surfaces or gilding, which is often applied over a rigid ground called gesso.

The response to relative humidity changes begins with determining the annual average RH for your particular climate. Then try to keep the RH in the space where your furniture is a close to that average as possible, generally within about 10% up or down. This stability can be achieved through de-humidifying in the summer and humidifying in the winter.

Be aware that raising the temperature lowers the humidity and vice versa. Thus, modern heating systems, which can drive down interior RH in the winter, almost invariably cause problems for furniture. To counteract their effect, you can modify the RH by keeping furniture-containing spaces cooler in the wintertime.

Mold, mildew and fungi are everywhere – on furnishings, walls, and in the air. But fungal infestation will occur only in the presence of an external moisture source or when the fiber saturation point (nearly 100% RH) is approached. Still air and high temperatures also encourage the rapid growth of these organisms. Molds and mildew growing on the surface of wood may stain it. Other fungi can completely destroy wood.

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Furniture, fabrics, computers, televisions, household appliances, books and video games, are just a few of the other items that people store that are effected by excessive temperature swings and excessive humidity. Don’t call any company except American Portable Mini Storage™ when it comes to storing your belongings. 1-877-4-1-TODAY.

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