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Hi all,
I'm building a desk out of some specrite merbau panelling that I bought.
I've been washing it every few days with Cabot's Deck Clean to remove tannins, but these dark green and black spots have appeared in the grain of one of the panels.
Are they an issue? Should I remove them before coating? What product would I use?
Welcome to the Bunnings Workshop community @HeloMaNemAri. It's sensational to have you join us, and many thanks for your question about merbau panels.
It's possible those dark green and black spots aren’t mould but rather natural mineral streaks or flecks that occur in merbau. This type of timber often contains black flecks or darker patches within the grain, and they can become more noticeable as the tannins leach out during the cleaning process. That said, if the spots feel raised, fuzzy, or have spread since you first noticed them, it could indicate surface mould or algae—especially if the timber has stayed damp between washes.
To be safe, I’d recommend giving the affected areas a light scrub with a diluted bleach solution (something like 1 part household bleach to 10 parts water), then rinse thoroughly and let the panel dry completely. If the marks remain but don’t feel textured or grow back, they’re likely just part of the wood’s character and nothing to worry about before coating.
Once fully dry, you can proceed with your chosen finish—just be sure the surface is clean, dry, and free of residue to ensure proper adhesion.
Please let me know if you have any questions.
Mitchell
