How to paint a merbau door frame

Bron

Hi, I recently had some new cedar French doors installed. The frame has a merbau base. I painted them myself with a water based paint but tannins from the merbau have leaked through the paint. On part of the base I sanded lightly and applied another coat of paint and there hasn’t been much further bleeding of tannins ( see left hand side on close-up photo below). Is this an adequate solution? Or do I need to sand all the way back to the wood and apply a primer?

JacobZ

Hi @bron,

Welcome to the Bunnings Workshop community, it is wonderful to have you with us.

What you’re seeing is pretty common with merbau because it is high in tannins which will bleed through water-based paints. Light sanding and recoating can slow it down, but it's unlikely that it will stop it completely because the tannins are still in there sealed in place.

A stain blocking primer such as https://www.bunnings.com.au/zinsser-1l-white-bulls-eye-primer-undercoat-sealer-and-stain-blocker_p1579690 will definitely help to hold back the tannins, but again, it doesn’t remove them it just seals them in.

So, for a more reliable, long term fix the best approach is:

• Remove the existing paint through sanding and scraping
• Use a tannin remover/cleaner such as https://www.bunnings.com.au/sikkens-1l-cetol-bl-tannin-and-oil-remover-1l_p1520482 first to draw out and neutralise the tannins
• Then apply a good stain blocking primer
• Then finish with your exterior paint system

If you skip the tannin remover, there’s still a chance the bleed can come back through over time.

So, your current fix isn’t wrong, and I can't say for certain that it won't work, but if you want to stop it from coming back with certainty, it’s worth doing the full prep and priming process, including tannin removal.

Let me know what you think and if you have further questions, please don't hesitate to ask.

Jacob