How to block Tannins when painting pine timber fence?

user2494

Hi brainstrust, 

looking for some advice. I have painted my 12month old pine timber fence with 2 coats of dulux weathershield (no under primer). Paint has been diluted at 15% as 10% wasn’t working the best with the Wagner sprayer. I am finding that tannins are coming through the paint which from my research did not expect to happen on a fence of this age. I’ve found i can wipe the tannins off when it’s wet within 12hrs but if it drys then the yellow remains. 

any advice on how to prevent this? Maybe I just wipe it off after painting but not sure if it will return

MitchellMc

Welcome to the Bunnings Workshop community @user2494. It's terrific to have you join us, and many thanks for your question about painting a fence.

I'm so sorry you've had this issue.

That looks like some pretty aggressive staining coming through the paint. Just to double-check, was the timber ever stained before you painted it, or is this straight raw pine? Normally, raw pine doesn’t bleed this heavily through a topcoat, but since you’ve used white, it’s not unusual that the tannins show quite strongly.

The main issue here is that topcoats like Dulux Weathershield don’t block tannins on their own. To properly stop the bleed-through, you’ll need to use a stain-blocking undercoat. The good option is something like Dulux Oil-Based Primer, Sealer & Undercoat. Clean as much of the tannins stain off as possible. Apply one coat over the affected areas and allow it to dry fully (24–48 hours). If you can still see signs of the stain bleeding through, apply a second coat to make sure it’s completely sealed. Once that’s cured, you can go back over the primer with two coats of Weathershield.

It’s a bit of extra work, but unfortunately, there’s no quick fix. The only reliable way to stop the staining is to lock it down with an oil-based primer so it can’t keep migrating through your water-based topcoat.

Please let me know if you have any questions.

Mitchell