Yellowing Problem in White Paint over Meranti Wood

To keep pigments in the wood from yellowing a water-based paint finish, pros recommend a sealing primer. November 25, 2005

We manufacture solid wooden doors from dark red Meranti and spray using white water-based paints. Every now and then we get yellowing in the sprayed finish across the whole of one component, say a stile or rail, so that the door looks like a patch work of white and light yellow components. Does anyone have any ideas? What could cause the whole of one component to get this consistent light yellowing?

Forum Responses
(Finishing Forum)
From contributor L:
This is occurring because it's wood and its a natural product. Color inconsistencies are normal when staining and spraying. You say that it is one component and throughout the one component. If you had splotches in random spots it could amount to technique, but it sounds just like the odd piece of material.

From the original questioner:
It is very uniform and consistent. I'm guessing it is either moisture or tannins in the wood, but its not yet confirmed.

From contributor L:
I guess one way to avoid this is to do a small test spray on each piece before it is assembled, but that is a pain. And if it takes time to yellow it makes it worthless to try. It's hard to make a color lighter once it's cleared.

From contributor G:
"We manufacture solid wooden doors from dark red Meranti and spray using white water based paints." Are you painting these doors a solid color? If so, use a primer. If not, use a sealer like vinyl or shellac to seal in whatever's leaking out of the meranti.

From Paul Snyder, forum technical advisor:
Starting with a tannin blocking primer will solve the problem.

From the original questioner:
It is a solid white finish so primer would be ok. I spoke with our paint manufacturer and they do either a stain blocker or an isolating primer. Im not sure what the difference is yet but I'll take their advice and maybe give them both a go and see which gives the best results.