Many people make the mistake of thinking "bleach" in woodworking terms is the same bleach we see in household use...
Bob Flexner, in the book "Understanding Wood Finishing" does an excellent job of explaining the different types of bleach and their individual uses. Flexner states "There are three types of bleach used in woodworking... Two-Part bleach (sodium hydroxide and hydrogen peroxide) removes the natural color from the wood. Chlorine bleach removes the dye from wood... And Oxalic Acid removes rust and water stains from wood."
Bleaching offers not protection for wood, its use is simply cosmetic. When discolored areas will not sand away, it is time to bleach. Bleaching will allow you to get the wood one color, so you can stain it the color you desire.
The bleach you probably already have in your house for laundry will likely work. Oak, ash, mahogany, maple, walnut, and beech woods, will absorb laundry bleach and turn it a lighter color. If you are working with darker woods, like a chestnut, poplar, cherry, rosewood, or cedar, you might need to purchase a 2-step bleach. They have these at any hardware store. With these you will need to follow the instructions on the bottle. They might have you neutralize the product with some vinegar.
With either product, you will need to clean the wood you are working with. Then, protect your eyes and hands. Bleach can be very potent, so work outside if you can. If you do not want your wood to lighten too much, mix the bleach with some white vinegar. A 50/50 solution should do. Once you put the bleach on, let it set awhile. You will see the wood turning lighter. When the wood looks the desired color, apply a neutralizer to stop the fading. Remember the wood will look lighter after it dries, so it's better to stop early. Apply a neutralizer; this can be warm water. Then, let the wood dry. Now you are ready to stain your wood. If the wood did not reach the color you wished, you can repeat the process until it is the light color you desire.
