Caring for Wood Art and Treasures (long)
Because wood is an organic material it is susceptible to damage that many other art materials are not. Heat, humidity, light, insect damage, mechanical damage, and fungal attacks are all possible with any organic material. This means that wooden objects require special care. Other considerations are the finish on the material. Certain kinds of finishes are susceptible to water damage. Unfortunately, there is no finish for wood that is completely water proof. Even wood objects that are impregnated with resins and polymers are not immune.*
Here are some suggestions to avoid problems:
Heat and Humidity
Heat and humidity are the twin bugaboos of conserving wooden art. Unless exposed to very high temperatures wood is not usually directly damaged by heat. What it does, however, is cause the wood to loose moisture. All wood, even that which feels very dry, contains some water entrapped in the wood structure. When exposed to excessive heat this moisture escapes which, in turn, causes the wood to shrink and change shape. Similarly, low atmospheric humidity can cause wood to loose moisture with much the same effect as excessive heat. People from the southwest should be particularly cautious with wood objects since this region has consistently low humidity. Likewise, winter heating can cause the humidity in a home to be very low.
These ill effects on wood can be mitigated by making sure that wooden art treasures are not exposed to rapid changes in either heat or humidity. Keeping them away from heat sources and storing them in tight display cabinets will buffer rapid changes in heat and humidity.
Light
Intense and constant exposure to light can also cause damage to wood. This damage usually occurs in two ways. The first is the bleaching effect that the ultraviolet component of light can have. The sun is, of course, the worst light source in this regard, but some fluorescent lights put out a significant amount of ultraviolet as well. The second way that sunlight can cause damage to wood is by solar heating. Wood tends to be dark and will, therefore, absorb infrared radiation which, in turn, causes the wood to heat up. Since the heating effect is generally superficial, it can be more damaging than a warm environment. The differential expansion of the wood surface versus the interior will cause greater stress on the wood's structure with potentially greater damage. Unfortunately, incandescent lighting is also often rich in infrared radiation, so it is best to keep your wooden treasures in low light environments except when actually being viewed.
Insect Damage
Insects seldom attack wood that is kept in a dry environment. But there are exceptions. Powder post beetles for example are notorious for attacking dry wood in homes and lumber yards. Signs of attack are a powdery substance, called frass, on or around the "victim". Additionally, small but obvious tiny holes may be present. These infestations can usually be stopped dead by freezing the object. If the object is small enough, place it in a heavy plastic bag and put it in a very cold freezer for 48 hours or more. If the object is large or valuable, contact a professional art conservator. Pest control people are not usually equipped to handle such cases. In any case, chemical pesticides should be avoided as there is a likelihood of adverse interactions resulting in unwanted color changes and damaged finishes.
General precautions against insect damage include avoiding bringing untreated wood (including firewood) into the home, keeping items in tightly sealed cabinets, periodic inspection and controlling the humidity.
Mechanical Damage
Bumps, scratches and dings happen when an item is loved and handled. Some may accept this "patina" and value the added character is provides. Others may want to keep their object pristine. In that case handle the object with cotton gloves and avoid contamination with oils and other fluids.
When a valuable item is mechanically damaged it is best to seek the assistance of a professional wood restorer or art conservator. Water damage is a particularly insidious form of mechanical damage in that it raises the grain of the wood. Depending on the nature of the object it may be possible to have it refinished. There are a few people who specialize in this kind of restoration although they may be difficult to locate outside of major metropolitan areas. However, the best solution is to contact the original artist (or someone of similar skill) to advise you on repairs.
Although not strictly in the mechanical damage category the use of aerosol spray waxes is strongly discouraged. If you know the finish on the object you may be able to renew it, but generally you should consult an expert before attempting to do so.
Mold
Mold and humidity go hand in hand. The more humidity the more likely a mold attack is. Given what was said about heat and humidity above you may think that this is some kind of a balancing act. Attempting to keep the average humidity between 40% and 60% will avoid most shrinkage and mold problems. If you live in a humid climate make sure that there is adequate circulation of air around and under the object. In the Pacific Northwest (where we live), objects placed directly in contact with the floor will often develop a coating of mold near the base. This can be avoided in two ways. Move the object occasionally and keep the object slightly above the floor. Plant nurseries carry a selection of "frogs" designed specifically for this purpose.
Mold is probably the most insidious kind of problem that you can have with your wooden objects. Mechanical measures such as vacuuming or wiping will only remove the superficial signs of the attack. The mycelia (what fungi use for roots) will remain as will many spores. Freezing will just cause the mold to sporulate (go dormant) only to emerge again when conditions are right. Boiling will probably kill the mold but that has obvious drawbacks. As do fungicides, which may discolor the wood or damage the finish.. Once an attack has occurred the best you can hope for is to keep the enemy at bay. So, the best tactic is to avoid the problem in the first place. Keep humidity in check. Do not expose to infected materials. Isolate any sources of mold until the problem is under control.
Cleaning
It is important to keep your wooden art dust free. Most wood is porous to a greater or lesser extent. As a result dust can accumulate in these pores. Dust contains mold spores making it a source of a potential fungal attack. Accumulation of dust can also permanently change the appearance of the work.
For objects that are not fragile the best way to clean them is with a vacuum equipped with a soft brush. For fragile items use canned air (available from professional photography stores and elsewhere) to gently blow away dust. Be careful not to let the liquid propellant spray directly onto the object as this can cause discoloration (voice of experience). Lint free clothes may also be used but they are not as effective as the vacuum, especially at removing dust from small pores and crevices. Under no circumstances should you use any paper product or rough material (terry cloth comes to mind) because they can snag on protruding wood fibers. Also avoid any colored clothe because the dyes could interact with the oils or finishes on the wood.
Summary
Although there seems to be a litany of things that can happen to wood, in reality, wood art can last and has lasted for hundreds of years. Regular cleaning, careful handling and adequate storage are all that are required.
*Much of this discussion is also relevant to natural fiber work such as basketry, fabric and paper.