Light varnishing variations offer a more translucent look, but the more transparent, the less UV ray protection, which requires more coats and more maintenance.  Clear finishes are a good option to provide a hard clear finish resistant to knocks, scratches, and chemicals.  When over time the sun penetrates to the wood causing a brittle, flaky surface, it must be refinished.  Varnish can be removed with chemical stripper or a heat tools.  Varnished exterior brightwork and restored wood looks beautiful but requires maintenance.  If left completely uncoated, it will weather gray, and eventually turn dark.  Dirt collects and black mold spores rot the wood.