After being in the buissiness since 5 yrs old now - 44 thought id bring to you attention that bleaching does not remove oil based stains. Well now id say about 90% of floors are oil based? Oil base stains allso asorb into the softer parts of the wood fibres creating undesirable effects. So if you cant sand out an oil base stain forget about bleaching it -it will be blotchy and worst then you started. Sincerely - custom furniture finisher -antique restorer -faux finish expert -chemical beta tester for major companies -Steve