Fungus on Wooden Furniture: Removing It and Keeping It Away

Mould needs moisture, something to feed on and still air, and a Goan monsoon supplies all three. Wood takes up moisture from humid air and swells, which is why drawers stick in August. A piece standing against an external wall sits in the coolest, dampest air in the room. And the surfaces nobody sees, the back panel, the inside of a carcass, the underside of a table, are unfinished, unventilated and dusty.

Surface build-up matters more than people expect. The Canadian Conservation Institute cautions that commercial furniture polishes usually contain waxes, oils or silicones that leave a sticky layer which attracts dust and dirt. In a humid climate that layer is also food. A piece that has been polished every week for years can be more prone to mould than one that has simply been dusted.

Surface mould is not the same as rot. Decay fungi that soften and break down timber need wood that stays wet, which usually means a leak, a floor that floods or a leg standing in water. If a screwdriver point sinks easily into the wood, or it crumbles, that is decay and needs a restorer. Powdery tunnels and mud tubes are insects, not fungus; our guide to termites and timber covers those.

Not every white mark on a table is mould. White fungus on wood sits on the surface as a fine, fuzzy or powdery growth, often in patches or spots, and it usually comes with a musty smell. Under a torch held at a low angle you can often see fine threads. It wipes away, and returns if the conditions do.

Bloom is different. It is a milky haze inside the finish itself, typically on shellac or lacquer finishes that have absorbed moisture. It does not wipe off, has no smell, and looks the same from every angle. It is a finish problem, not a living growth, and scrubbing it with water and detergent makes it worse. Leave it for a French polisher or furniture restorer. A third possibility on old pieces is whitish residue from old wax or polish, which feels waxy rather than powdery. If unsure, clean a small hidden area first.

Airflow is the cheapest protection. Pull furniture a few centimetres away from external walls, and keep it off damp floors. The US National Park Service advises museums to store objects at least four inches, about 10 cm, above the floor and not directly against outside walls, where humidity, condensation and leaks are worst. The same logic applies to a sideboard in a monsoon living room.

Humidity is the real control. The Park Service's guidance for collections is 45–55% where possible and always below 65%. In a Goan house that means a dehumidifier or air conditioning in the rooms that hold the best pieces, with the room kept closed while it runs; our guide to humidity in Goa covers sizing and running costs. In the rest of the house, open doors and drawers on dry days and run the fans.

Keep surfaces clean rather than polished: dust with a soft, dry cloth, and skip the spray polishes. Never cover furniture in plastic for the monsoon; it traps moisture against the wood. Use cotton dust sheets. Silica gel helps inside closed spaces such as a glass-fronted cabinet or a drawer of silver, where the Park Service notes it can buffer humidity, but it saturates in an open room, and it needs drying out to keep working.

Many older Goan pieces carry a French polish (shellac), a wax finish, or an oiled surface, sometimes all three from different decades. For any of them, the conservation advice is restraint. The Canadian Conservation Institute recommends paste wax applied thinly and evenly, and notes that a thorough waxing lasts for many years; waxing should not be frequent. Heavy, repeated waxing builds up the same dust-holding layer as spray polish.

Stability matters as much as dryness. Wood swells and shrinks as humidity changes, and the Institute singles out veneered pieces and those with metal fittings across the grain as most at risk of splitting and lifting when humidity swings. After a closed monsoon, bring a room's humidity down steadily rather than switching on hard air conditioning at full blast on the first day. Heritage houses have their own considerations, from fixed built-in cupboards to furniture that was made for rooms with far more through-ventilation than they now get. Our pieces on heritage villa interiors and restoring an old Portuguese house look at those in more depth.

Call a furniture restorer or conservator when the wood is soft, crumbling or split, when veneer is lifting, when the finish has turned milky, crazed or sticky, or when mould keeps returning to the same piece after proper cleaning and better conditions. The US National Park Service advises consulting a conservator before treating significant objects, because inappropriate treatment can do more harm than the mould. The same applies to any piece whose value is historic rather than practical: a carved bed, an old contador, a piece with original painted decoration. The cost of a conservator's visit is small against the cost of stripping a two-hundred-year-old finish by mistake.

Upholstered chairs and settees add a further layer, because the stuffing and webbing can hold mould long after the frame is clean. If a seat still smells musty once the wood has been treated, the upholstery itself may need to be redone; that is part of what our reupholstery work covers.