On wooden surfaces, as with other types of surfaces, it is always safe and important to first clean a test area. In wood, pressure and water might damage the material or drive the paint deeper into the wood. Even low pressure spraying can create such problems, so test it first.
If a pressure washer is being used, it’s a good idea to start off with a test area. Different pressure settings must be tested on the surface to prevent surface damage. Also, using a wide spraying pattern avoids any paint etching onto the surface or area that is being cleaned. An extra amount of care is needed when cleaning old masonry walls, because they are more prone to crumbling. While cleaning out the test area, make small and medium adjustments to determine the right pressure and pace for the particular surface being worked on.
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