The Care Of Antique Furniture
Environmental Conditions
Humidity will vary between “Too High” at a Relative Humidity (RH) of 70% to “Too Low” at 30% RH. It is important to minimize the fluctuations as much as possible because with every change all the wooden members, that together make a piece of furniture, will move independently. Wood expands in its width and thickness (across the grain) but makes no significant adjustment in its length (along the grain). Rapid daily changes are very much less of a concern than are those created seasonally, especially since the advent of central heating.
Museum and other owners of large collections of furniture strive, with the aid of humidity control machines, to maintain an even RH. People in the private sector should also try to emulate the “professionals”, but only if the quality of their antiques warrants both the expense and trouble of maintenance that humidifiers and dehumidifiers demand. In periods of extreme dryness wet cloth draped over radiators or purpose made “humidity wicks” hung on them, may make a modicum of difference. It would be more effective to lower the background temperature and use local heat only when necessary.
Cold Outside + Warm Inside = Dry Conditions Shrinking timber causing opening-up of the joints, warping, splitting & cracking and torn veneers.
Warm Outside + Cool or Warm Inside = Damp Conditions Expanding timber causing Warping and Compression Stresses – internal damage to the cell structure of the wood, which adds, in time, to additional shrinkage.
A warm and damp environment accelerates chemical action. Materials which become chemically unbalanced, such as leather (particularly of the late nineteenth and early twentieth centuries), paper and textiles are at risk. A damp environment will cause dust-covered metals to be severely damaged. Marble too can become stained from dust in similar conditions. Bronze mounts are susceptible to Bronze Disease, the appearance of blue/green copper on its surface, in a warm damp acid environment.
All light and daylight in particular, contains Ultraviolet light – the wavelength of light that is most damaging to colours of both dyed and natural woods and textiles. Direct sunlight also heats up the parts of objects it falls upon. This warm dry microclimate is evidenced in damage to surface coatings, veneers and the underlying adhesive. The exposure of Oriental Lacquer to daylight should be kept to a minimum, while the whiteness of ivory may be enhanced by shaded daylight.
Biological Conditions
The common furniture beetle (Anobium punctatum) is, or has been, more responsible for rendering furniture unsafe than perhaps any other factor. Fortunately today, eradication of the pest is relatively simple. There are three systems currently used :
Brushed, sprayed and/or injected liquid insecticide
Enveloping the object in a gas, either as a direct poison or as a means of excluding oxygen.
More recently a heated humidity controlled environment has been used with excellent results.
Occasionally furniture has been infested by the deathwatch beetle (Xestobium rufovillosum). The insect needs damp wood which supports a fungal growth, which in turn makes the wood digestible, before it can set up home.
Georgetown Refinishing & Antique Restoration
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