Artcare - Auckland Art Gallery

WoodWooden objects range in size from small boxes to largecanoes. In many cases they are not solely made of wood,but include materials such as metals, glass, shells, feathers,etc. When caring for artefacts made of a variety ofmaterials the preservation requirementsof each must be taken intoconsideration and if neccessarycompromises made to ensure theoverall preservation of the object.Causes of DeteriorationExtremes of temperature, fluctuationsof humidity and biologicalattack are principally responsiblefor the deterioration of wood. Thisapplies equally to carvings, andornaments such as combs, artefactssuch as digging-sticks, bailers, weaponry, canoes, andfurniture.Temperature and Humidity—extremely hot and dryconditions will cause wood to shrink and crack.Alternatively, cold and damp conditions will cause woodto swell and warp. Sudden fluctuations in temperatureand humidity will accelerate these processes. For example,wooden items obtained in moist tropical regions andtransported to drier countries commonly develop seriouscracks as moisture is lost from the wood. This canbe seen in collections brought back from Melanesia bymissionaries in the 19th century, and in modern-daycarvings from Papua New Guinea. Similar damage mayoccur if items composed of wood are exposed to hot sunlightduring the day and to cold conditions at night.Biological—wooden artefacts in museums are particularlysusceptible to attack fromthe common house borer and, to alesser degree, the New Zealand drywoodtermite. Fumigation withmethyl bromide is an efficientmethod for dealing with borer, butthis can only be carried out by registeredpest controllers and is soonto be banned in New Zealand. Donot use home-made remedies asthese can grossly discolour woodwithout necessarily eliminating thepests. In some cases borer infestationswill be restricted to a small part of an artefact andthis can be treated with a commercially available pesticide.Before using such a product contact a conservatorfor advice as to whether it is the appropriate treatmentfor your infested artefact.Surface moulds such as mildew and wood-rottingfungi are potentially destructive to museum collectionsand to buildings. They thrive in damp and unventilatedconditions. Carvings are particularly susceptible to dryrot and should be inspected regularly to see whether oldinfested areas are still dormant and that new growthshaven’t developed (see also page 7).44