Blackening Reaction Between Wood and Metal
Wood tannins react with iron to form black-staining iron tannate; oxalic acid can remove it. November 18, 2006
One of our customers purchased black cherry lumber from us to be planed into flooring, but we got reports from the job site that some of the cherry turned dark in the areas where it had been in touch with metal. For example, where a can of finish had been sitting for a while, a dark ring remained. Reportedly it was not due to any leaking finish.
Does anyone know of chemical reactions between black cherry and any metals? If so, which ones? I haven't seen any pictures yet myself, so I can't offer any more information.
From Gene Wengert, forum technical advisor:
Many woods have tanic acid that reactions with iron to form iron tannate. Iron tannate is black in color. It can be removed instantly by putting a little oxalic acid (see a drug store pharmacist) on it. Unfortunately, with cherry, the acid may turn the wood a deep red.
Would you like to add information to this article?
Interested in writing or submitting an article?
Have a question about this article?
Have you reviewed the related Knowledge Base areas below?
KnowledgeBase: Knowledge Base
KnowledgeBase: Finishing: General Wood Finishing
KnowledgeBase: Woodworking Miscellaneous
All rights reserved. No part of this publication may be reproduced in
any manner without permission of the Editor.
Review WOODWEB's Copyright Policy.
The editors, writers, and staff at WOODWEB try to promote safe practices.
What is safe for one woodworker under certain conditions may not be safe
for others in different circumstances. Readers should undertake the use
of materials and methods discussed at WOODWEB after considerate evaluation,
and at their own risk.
335 Bedell Road
Montrose, PA 18801
Copyright © 1996-2019 - WOODWEB ® Inc.