It is hard to believe it is almost April already. Spring is finally here with all its changes, warmer weather and higher humidity. As spring turns to summer and our temperatures and humidity rise, it is important to remember that these changes also affect our valuables. Rapid and frequent fluctuations in relative humidity create stress as materials change shape. Alternately absorbing and losing moisture increases internal stresses in materials such as wood, paper, and fabrics. At some point, fibers lose their malleability and splits or cracks develop. Composite objects are most dramatically affected because different materials absorb and lose moisture at different rates, resulting in buckling, splitting or flaking.
Extended periods of high humidity (over 65%) and elevated temperatures can promote mold and mildew and accelerate chemical deterioration. Mold and mildew not only stain organic fibers but can actually destroy them. Warmth and moisture also promote chemical reactions causing metals to corrode, plastics to soften, and photographic emulsions to become sticky. As temperature and humidity rise more moisture becomes available for these reactions. The rate of a chemical reaction doubles for every rise in temperature of 18 degrees Fahrenheit. Alternately, relative humidity below 30% can cause organic materials to dry out, causing fibers to shrink and distort. Paper, textiles and leather may become dry and brittle. Wooden objects and furniture may crack and split. Glues may weaken, causing joints to open and veneers to peel.
The key is to avoid extreme fluctuations and provide a relative humidity that is as constant as possible. Museums monitor temperature and humidity with instruments called hygrothermographs. Simpler equipment is adequate for home use and a wide variety of instruments for any budget are available. I can assist you in finding something that is right for you. Dehumidifiers are an important tool in removing the excess moisture and are also readily available. Most dehumidifiers have a % setting for you to specify how much humidity you want in the air. The museum ideal of 70 degrees Fahrenheit and 50% humidity may not be practical for your home. Remember, although extremes are dangerous the fluctuations can cause the most rapid damage.
Common sense should be your guide in placing your valuables throughout your home. Direct sunlight, which I will discuss in future post, should be avoided. Attics (or basements) are not good places to store important items. Mud rooms and vestibules are designed to buffer extreme swings in temperature and humidity preventing the swings in interior spaces. Hence, they are not good locations for cherished photographs, fine paintings, or heirloom furniture.
If you have any questions or would like more information, please feel free to contact me at 239-514-0084. Information for this post is from Caring for Your Family Treasures, by Jane S. Long and Richard W. Long.
