damage and repair
Tannin Reaction — Why Pet Urine Turns Oak Black
The chemical reaction between urine salts and wood tannins that creates dark black stains in oak and similar species.
Published
What it is
Oak, walnut, and cherry contain tannic acid. When pet urine breaks down and releases ammonia plus iron salts, it reacts with those tannins to form iron tannate — the same chemistry as iron-gall ink, creating the classic black halo stains.
Why it matters for your wood floors
This entry is part of our complete glossary covering every term homeowners, realtors, and contractors encounter when dealing with wood floor cleaning, recoating, and refinishing. For full context, see our main guides on recoating, chemical abrasion, and the services we offer.
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