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Warning: Tried water-based polyurethane on a red oak vanity and it turned green
I finished a bathroom vanity for a client in Portland last month using water-based polyurethane over stain. The wood turned a weird olive-green color after the first coat. I learned the hard way that red oak has tannins that react with water-based finishes. Has anyone else run into this problem with certain woods?
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rileyb611mo agoMost Upvoted
Hold up though, red oak's reaction to water based poly is way overblown online. People mix up tannin bleed with actual color shift. Real olive green only happens if you use a non-sealing stain or skip a proper barrier coat entirely. A shellac sealer or a dedicated stain blocker underneath would have prevented that completely, no matter what finish you used on top. Your client's vanity just needed a coat of dewaxed shellac first. Plenty of pros use water based poly over red oak every day without issues because they prep right.
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hollyl4512d ago
Bob Flexner's right about tannins causing trouble, but it's more about the prep than the finish itself. In my experience, just one coat of dewaxed shellac as a sealer does the trick every time. I've done dozens of red oak vanities and tables with water based poly and never seen green unless I got lazy or the customer insisted on skipping the barrier. A stain blocker like Zinsser BIN also works fine if shellac's not your thing. That client's problem probably came from going straight to poly over bare wood or a tinted stain that didn't seal.
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diana_black1mo ago
Didn't Bob Flexner say something about tannin bleed causing weird color shifts with water-based finishes?
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