The Furniture Conservation Lab cares for and treats about 9,000 pieces of furniture and wooden objects in the collection. Historic surfaces, both transparent and painted, change and deteriorate over time, resulting in crackling, flaking, uneven darkening, fading, blanching, scratches, and stains. Furniture conservators are concerned with both structural and surface issues. Conservators maintain and stabilize the structure of objects that may have been damaged or poorly repaired in the past, that suffered an insect infestation, or were weakened by exposure to water or a poor environment. They balance preserving early surfaces and the history they embody with maintaining an aesthetic appearance that respects the intent of the original maker.
Working with textile conservators, furniture conservators also care for upholstered furniture. They preserve and stabilize existing upholstery structures and show fabrics when they are historically appropriate and in stable condition. When the upholstery is inappropriate and/or the structure or show fabric is too deteriorated, conservators replace it with a non-invasive structure that avoids nailing or tacking into the original wood.
To reduce the risk of damage to its furniture collection, Winterthur maintains a stable environment with an average temperature of 68 degrees to 70 degrees and a relative humidity of 45 percent to 55 percent. A stable relative humidity is especially important to furniture since rapid changes cause different parts of the object to expand and contract at different rates and to different degrees, causing problems such as detached veneers, cracks, and flaking paint. Since insects like the powder post beetle can cause serious damage to wooden objects, preventive conservation aides carefully monitor for evidence of insect activity. Excess light can cause surfaces and upholstery fabrics to fade or darken so exterior windows are modified to reduce ultraviolet and visible light. Wintethur lighting specialists design interior lighting to minimize damage.