There is no one solution or chemical that is right for every job.  Knowledge of wood species, sealers and chemical reactions are all factors in determining the best course of action for wood restoration.  For wood restoration its best to go with the rule of conservation which means using the mildest treatment that gives acceptable results.

• Sodium Per-carbonate –  Advantages to sodium per-carbonate wood cleaners include; ease of use, emulsifies dirt, safe for vegetation, wood color retention and does not cause respiratory distress.  The emulsification of dirt allows for easier low pressure cleaning.  Disadvantages to sodium per-carbonate is a slightly higher cost of materials and requires a longer dwell time to effectively kill mold.  In some extreme cases it may not be able to eradicate mold completely.  Sodium per-carbonate by itself is an Alkaline(basic) with a pH around 10.5.  To neutralize we also apply oxalic acid based brighteners and rinse.
• Sodium Hydroxide – This chemical is primarily used to emulsify previous coatings of stain, dead wood and dirt. When you purchase a pre-formulated stripping solution,  surfactants, buffers and other misc. chemicals are added to work in synergy with NaOH.  Sodium Hydroxide is extremely caustic and will irritate eyes, skin and respiratory system.   Follow the manufacturers guidelines for personal protective equipment (PPE).  Pure Sodium Hydroxide(basic) ranges between 12 and 14 on the pH scale. To neutralize we apply citric/oxalic acid and rinse.
• Sodium Metasilicate – Sodium metasilicate is a cleaning agent that can be used on its own as a cleaner for wood and metal and as an ingredient for other products like soaps and detergents. Chemically speaking, sodium metasilicate is known as an alkali salt, which gives it great stain lifting properties and the ability to kill off mold, moss, and other organic growths on your wood. Sodium metasilicate, if mixed with a high enough concentration, could also be used to strip wooden decks to prepare them for their new coat of paint, varnish, or sealer.

See should I choose water or oil based stain and why use a deck brightener for further information.