Ron, As Bruce said, wood bleach is oxalic acid.
Vinegar has acetic acid. They are both mild acids. Oxalic acid is a frequent ingredient in many boat cleaning products. It is useful for removing the "bow mustache" some boats get when sailing in waters with tannins and other brown staining constituents. https://www.amazon.com/Oxalic-Acid-Bleaching-Wood-Net/dp/B001F2US4U The advantage of using a mild acid is control. You may have to make multiple applications but you can control the rate of bleaching. Dennis C. Touche' 35-1 #83 Mandeville, LA
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