Removal Of Stains and Tannins in Oak

Posted 07/03/2017 - by Charlotte Clemons in Blog, Oak Finishing, Treating Oak

As many will know a lot of our jobs include building and renovation, in particular Oak frames, Oak windows, beams  and  Oak  flooring.  Oak can become discoloured fairly easily having oak, especially green oak looking aged and in need of some TLC.  Another common staining in oak is when Tannins* ( the chemicals in the sap) come into contact with iron. Together a reaction occurs and forms a blue-balk stain on the oak.


Water, tide marks and Iron stains can be removed by scrubbing the stained area with a solution of oxalic acid in water. Dissolve 1kg oxalic acid to 6Lt of warm water. Scrub stained area using a stiff-bristle brush. Thoroughly rinse with water after treatment. When completely dry, lightly sand the surface. Surface must be clean and completely dry (not just surface dry) before refinishing.

Use an oil or  wood stain for a perfect finish.


To restore the natural oak tones of the wood use 75-125g of oxalic acid per 5lt of hot water then apply by spray, brush or wipe on.


NB: Oxalic acid is an ACID and therefore the correct protective equipment should be used- should your skin or eye come into attention SEEK MEDICAL ATTENTION URGENTLY.