Mold on Wood Furniture

The first question is whether the wood is finished, because it determines whether the mold is on the piece or in it.

Finished wood — varnish, lacquer, shellac, paint, wax. The finish is a barrier and the mold is growing on the surface film, on dust and skin oils, not on the wood. It wipes off, and the wood underneath is usually untouched.

Bare or unfinished wood — the undersides of drawers, backs of cabinets, raw pine, the inside of a chest. Cellulose is food, the grain is porous, and hyphae go in. Wiping removes the visible growth and not the colony.

Look at the back and the underside, not the front. That is where furniture is unfinished and where it faces a wall.

Before touching it

Take it outside. Cleaning mold indoors disperses spores into the room and turns one problem into several. A garden, a garage with the door open, a driveway — anywhere with air movement.

Wear an N95 or better, gloves, and eye protection. A cloth dust mask does nothing for spores.

If it cannot be moved, seal the room off, open a window, and use a fan blowing outward rather than circulating.

Finished surfaces

1. Vacuum first, with a HEPA filter and a brush attachment, holding the nozzle slightly off the surface. This removes loose spores before you smear them.
2. Wipe with a cloth dampened in warm water with a little washing-up liquid. Damp, not wet.
3. For stubborn areas, distilled white vinegar or a 1:1 rubbing alcohol and water mix. Test on a hidden area — alcohol softens shellac and some lacquers.
4. Dry immediately and thoroughly. Leave it in moving air for a day.
5. Re-wax or re-oil once fully dry, to restore the barrier.

Avoid soaking, avoid bleach — it damages the finish, raises the grain, and does not reach anything a detergent has not already reached — and avoid ammonia on shellac.

Bare wood

More work, and it is genuine removal rather than cleaning.

1. Vacuum with HEPA.
2. Sand the affected area with 120 grit, then 220. This is the actual removal step: you are taking away the wood the mold is in.
3. Vacuum again, then wipe with a cloth dampened in vinegar or a dilute borax solution — borax leaves a residue that inhibits regrowth, which is why it suits unfinished surfaces.
4. Dry completely. Days, not hours, if the piece was damp.
5. Seal it. A shellac, oil or varnish barrier is what stops it recurring on wood that has already proved it will host mold.

Sand outdoors, with a respirator. Sanding mold indoors is one of the more effective ways to distribute it through a house.

Upholstery and inside drawers

Fabric is a different problem. Removable covers can be washed hot; fixed upholstery with significant mold growth generally is not worth saving, because the growth is inside the foam.

Drawer interiors, being bare wood in a closed box, are where the problem usually starts and where it usually returns.

When the piece is not the problem

Furniture molds because the room does. If a piece has grown mold, look at:

• The wall behind it. Furniture against an exterior wall creates a cold, still pocket where condensation forms. Pulling it 5 cm off the wall frequently resolves it permanently.
• Room humidity. Above 60% relative humidity, mold grows on whatever is available. A cheap hygrometer answers this and is the single most useful thing to own if you have recurring mold.
• Basement or garage storage. Both run humid, and both are where stored furniture molds.
• A leak. Persistent growth in one spot means water arriving.

Cleaning the furniture without changing any of that returns you to the same position in a season.

Dry rot, which is not this

Worth ruling out on structural or antique wood. Dry rot — Serpula lacrymans — is a wood-destroying fungus, not a surface mold. Signs: the wood is cracked into cubes, crumbles under a screwdriver, smells strongly mushroomy, and there may be white or grey strands spreading across surfaces.

That is a building problem rather than a cleaning problem and needs a surveyor. The distinction between something growing on a surface and something consuming the material is the same one that runs through is it even mold.

When to let it go

If the piece is inexpensive, was stored damp for a long time, is upholstered and heavily affected, or is chipboard or MDF that has swollen — the work exceeds the value. MDF in particular disintegrates once wet and cannot be sanded back to sound material.

Removing mold covers the same judgement for building materials, where the threshold for calling someone in is lower than most people assume.