If you can’t live with the way your exterior wood looks the finish must come off and you need to restore the wood.
The difference between maintenance cleaning and restorative cleaning is the choice of cleaners.
When it comes to restorative cleaning you do have to be more aggressive with the cleaner selection. You might even find that an aggressive cleaner is not enough. If so, you need to seriously consider hiring a professional.
Super Alkaline Cleaners
When it comes to sheer cleaning power the number one work horse of the cleaning industry is caustic. Caustic can be found in many different “sizes”. The largest molecular size is sodium hydroxide (caustic soda) then potassium hydroxide (soda ash), on down to orthosilicates, metasilicates, and so on, etc. Picture it like a wrecking ball. The larger the molecule the bigger the cleaning power. The larger the molecule the more potential damage to the wood itself as well.
Mix and Test the cleaner solution on a few spots before committing to the whole job. Some finishes will come off very easily with a little bit of caustic. Some won’t come off at all.
The methodology for restorative cleaning is the same as the maintenance cleaning methodology. However, restorative cleaning caustics do have free caustic. They will eat into finishes and wood, can etch glass, metal, and paint and possibly burn you severely. Be sure to protect surfaces you don’t intend to strip prior to applying the cleaner with masking or wet things down like flowers, shrubs or grass. Definitely wear a mask and eye protection when you are mixing or spraying these solutions.
Never make the mistake of thinking that a super alkaline cleaner can be diluted enough to work as a maintenance cleaner. You won’t know how much free caustic you are dealing with and too much free caustic can ruin an otherwise easy maintenance coating.