is a very important tool used in the cleaning and restoration of wood.  Power washers are also widely misunderstood. Just like any other power tool, if not used properly, it can do a lot of damage.  But when used by a professional it is very effective.  There are many different levels of power washing.  A new deck will only require a light cleaning with minimal pressure.  Older decks that have grayed out will require a more heavy duty detailed cleaning.  Anytime wood is cleaned with a power washer or a scrub brush, you will see raised grain. The softer the wood, the more raised grain there will be.  Also, different grain structures are more susceptible to grain raising than others are.  Some grains can literally be lifted with the pick of a fingernail.  When raised grain occurs, a light sanding with 80-100 grit sand paper is all that is needed to quiet the grain back down before sealing.