Dust Nibs in the Topcoat

Tiny bumps in a freshly cured floor finish, almost always dust that landed in the wet coating. Stop the dust at source instead of trying to filter it out of the air.

What dust nibs are

Tiny bumps protruding from a cured polyurethane surface, usually visible when you run your hand across the finish or look across the floor under raking light. Each one is a particle of dust that landed in the wet coating before the surface skinned over.

Where the dust comes from

Most installers blame airborne dust from outside -- it's usually closer than that. Audit each source:

Sanding dust still in the room

Even with extraction running, fine particles settle on walls, ledges, window sills and skirtings. When you walk in to coat, you stir them up and they fall into the wet film. Wipe down all horizontal surfaces above the floor with a damp cloth before coating. Don't just vacuum the floor -- vacuum the walls.

Your clothes

Pants and overalls hold sanding dust like a sponge. Change clothes between sanding and coating, or wear a Tyvek suit for the coating pass. Boots especially -- bag them up between sand and coat.

The HVAC

Air conditioning and ducted heating circulate dust. Turn it OFF for the entire coating window and for the first 30 minutes after the last coat goes down. Tape over return vents if they're in the room.

Other trades

Painters cutting in next door, plasterers sanding render, anyone using a circular saw within earshot. Lock the room before you start.

Dust extraction during sanding

Less dust in the air during sanding means less dust on the surfaces around the room means fewer nibs in the finish. Bona's dust extraction equipment (DCS 50, DCS 70, FlexiSand integrated extraction) connects to the belt and edger and pulls the bulk of the dust out at source. If you're still using a passive bag, every job will fight nibs. Sand-Aid orders DCS units in on request.

How to recover from nibs in a cured coat

If the nibs are small and the floor is otherwise clean, screen and recoat: light pass with a maroon pad or 240-grit screen knocks the nibs back, then one fresh coat over the top. If the nibs are bad or the surface looks gritty, sand back the topcoat and re-coat from primer.

Intercoat abrade is your insurance

Always abrade lightly between coats. A maroon pad on a buffer takes 10 minutes and removes any nibs that landed in the previous coat. Skipping intercoat abrasion is the single biggest reason nibs compound from coat to coat.

Related: Process FAQs →