There can be many reasons that a wooden sword becomes stained and needs bleaching. The most common reasons are simply the accumulation of oils from your hands mixed with natural grime, or your sword has become wet and changed color. The actual bleaching of a wooden sword is not difficult. The trick is in knowing what type of wood your sword is made from and knowing what caused the stain in the first place. There are several different types of wood bleach and they are not interchangeable.
Purchase a quantity of bleach of the type that is specific to the type of wood that needs bleaching. Use appropriate precautions such as gloves and eye protection and use a dust mask when mixing powdered bleaches.
Bleach dark water stains on oak, mahogany and cherry with Oxalic acid. This is a bleaching agent found in most deck "brighteners." Ask at your local hardware dealer for products that contain Oxalic acid. Mix the Oxalic acid crystals with hot water per the manufacturer's instructions. Moisten a rag with a strong solution of the acid and rub the affected area vigorously. Do not be afraid to apply a second or even a third coat of the acid to particularly difficult areas. If necessary allow the acid to dry overnight and then apply another coat the following day. Once stains have been removed, wipe the blade with a damp rag to remove as much acid residue as possible and then wipe on a solution made from one quart of warm water and two heaping tablespoons of baking soda. Add a finish to the sword soon after drying.
Use a strong chlorine bleach to remove stains caused by dyes. Clorox bleach is not strong enough for most dye-based wood discolorations. Instead use dry calcium hypochlorite which you can purchase from a swimming pool supplier. Apply a liberal mount of the solution with a rag. Many dye stains will disappear almost immediately. For stubborn stains wait overnight to evaluate the full bleaching action and then apply more bleach if necessary. When dry you will need to neutralize the bleach by rubbing your sword with a rag dampened with one cup of white vinegar and two cups of warm water. As soon as dry apply your final finish.
Remove all color from your wooden sword with A/B bleach (sodium hydroxide and hydrogen peroxide). A/B bleach can be found at most hardware stores. The mixture must be used immediately. One coating of this bleach combination should be sufficient. If bleaching is not uniform a second coat may be necessary. When finished, neutralize the bleach by rubbing with a rag dipped in a solution of one cup white vinegar and two cups of water. A/B bleach will not work on ebony.
Sanding may be necessary for certain types of stains. If bleaching does not remove a stain, then you may need to resort to sanding.