Eventually a painting will need to be cleaned. Dust, grime and the natural absorption of the first original varnish layer will require a light dusting and revarnishing. This is usually recommended when the painting is still fairly new; within the first five years. After that, a revarnishing (without removing the underlying varnish) every generation or so will protect the painting and keep it looking exceptional. Eventually the painting may become heavily grime laden, or the layers of varnish may oxidize or deteriorate and a chemical cleaning (removal and reduction of the protective varnish layers) can be undertaken by SBC.