Tannin Bleed on Blackbutt

Green or grey staining through a freshly coated blackbutt or tallowwood floor is tannin bleed. Here's why it happens and how to stop it before it bites.

What tannin bleed actually is

Australian hardwoods store natural tannins in the cell walls. Blackbutt, tallowwood, spotted gum, ironbark and some of the stringybarks carry a lot of it. When you apply a water-based coating directly over freshly sanded boards, the water in the coating pulls those tannins out of the timber and up through the film while it cures. The finished floor ends up with a dull grey-green haze across it that most clients describe as looking "mouldy" or "dirty." Polish it and the haze stays. Sand it back and the next coat does the same thing.

It's not a coating defect. It's water pulling a timber extract up into the film before the film can seal itself. Solvent-based finishes didn't show it as much because they don't carry water. As the industry moved to water-based for safety, tannin bleed became the single most common callback on Australian hardwood floors.

How to tell it's tannin bleed (not something else)

Three quick checks:

• Species. If it's blackbutt, tallowwood, spotted gum, ironbark, jarrah or Sydney blue gum, tannin bleed is the first suspect. If it's oak or Tasmanian oak, it's almost certainly something else (dust, fish-eye, moisture).
• Colour. Tannin bleed is grey-green to olive. If the haze is white, that's moisture. If it's yellow-brown, it's usually shellac or solvent contamination.
• Pattern. Tannin bleed is even across the whole floor or concentrated around darker knots. If it follows the sanding direction it's sanding marks, not tannin.

The fix: prime before you coat

The only reliable fix is a proper tannin-control primer under the topcoat. Bona Prime Intense is formulated specifically for high-tannin species -- it seals the tannin in before your water-based topcoat ever touches it, and as a bonus it pops the natural colour of the timber so blackbutt actually looks like blackbutt.

Sequence:

• Sand through the normal grit sequence to a fine finish. Don't skip grits.
• Dust off thoroughly. Residual dust under the primer will show up in the topcoat as nibs.
• Roll or T-bar one coat of Bona Prime Intense at ~8 m²/L. Let it dry the full 1-2 hours.
• Light intercoat abrade if the grain has raised.
• Two coats of your topcoat -- Traffic HD for commercial, Traffic GO for faster residential turnaround, Mega for straight residential, or Wave 2K for heavy residential at a friendlier price. All of them play fine over Prime Intense.

Why Classic UX isn't the right primer here

Bona Classic UX is the everyday primer for most species -- natural tone, great filling ability, easy intercoat abrade. But it's specifically not recommended on high-tannin species because it's a neutral sealer, not a tannin-control formulation. On blackbutt and tallowwood it won't stop the bleed. Use Classic UX on oak, Tasmanian oak, American oak, messmate, brushbox. Use Prime Intense on anything with a tannin-bleed reputation.

Already got bleed on a finished floor?

You have to sand back. Screen or recoat won't hide it -- it's in the film, not on top. Back to bare timber, prime with Prime Intense, then topcoat. Tell the client upfront; don't try to polish over it and hope.

Species Sand-Aid sees this on most

• Blackbutt -- classic offender. Always prime with Prime Intense.
• Tallowwood -- high tannin, goes grey fast. Prime Intense every time.
• Spotted gum -- can go either way. Prime Intense is the safe call.
• Ironbark -- heavy tannins on wet boards. Prime Intense.
• Sydney blue gum -- moderate risk. Prime Intense recommended.
• Jarrah -- lower risk but still worth priming on water-based systems.

Related: Species FAQs →