isolation coat

The purists would answer that watercolour paintings should be behind museum quality, anti-reflective, conservation UV filtered glass, and confined within a frame. And most watercolour paintings are, as this used to be the only option for exhibiting your watercolour artwork. However there are many more presentation options for watercolour artists to consider once their work has a protective varnished final layer. 

A varnished acrylic painting will have greater longevity, as varnishing will protect the surface from permanent damage from a number of airborne pollutants including dust, smoke and steam.